What is Spring Boot

What is Spring Boot

This will be a short post more focused towards introducing Spring Boot, We will discussWhat is Spring Boot“? and how Spring Boot is helpful in building Java based enterprise applications.

 

Introduction

As a Java developer, it’s very likely that we have worked with Spring Framework based application directly or indirectly.Spring has a number of ways to configure its behavior, it provides the option to use XML based configurations or to use Annotations, JavaConfig is becoming the de facto standard for the new Spring based applications.Although these options seem really good, with large enterprise applications involves hundreds of modules and complicated business rules, these configurations can become really complicated. Below are some of the complications which large application can bring in to the picture

 

  • Each module has its own configurations.
  • Each module contains its own set of dependencies (third-party dependencies)
  • Upgrading application (e.g Spring 4.x to 5.x) will be complicated as we need to ensure that all required dependencies are upgraded correctly.
  • In case some of the dependencies are not working correctly, trying to find out root cause is a large application is really complicated and challenging.

 

All above issues are more or less related to making sure we have everything before dev team can start working on actual tasks. Now let’s talk about another use case which we use to do with any Spring based application, Let’s say we want to create a web-based application, these are most common steps most of us will be doing on regular basis

 

  • Create a web application using Maven or IDE of our choice.
  • Copy standard web application configurations (web.xml configuration for Spring MVC application).
  • Tweak above configurations based on our requirements.
  • Configure Spring MVC standard beans like ViewResolver, MessageSource etc.
  • Configure Database properties to be used for our application.
  • Establish DB layer and ensure underlying DB connection is in place before we can start using it (EntityManagerFactory, TransactionManager etc.)

 

This list can grow significantly based on type of our application

 

 

1. What is Spring Boot

All of the above steps seem very to us but they add a lot of overhead to the development team and instead of focusing on solving the actual business problem, initial time will be consumed to ensure that everything is in the correct place to start work. Think of Spring Boot as a tool which can do these initial tasks for us automatically.Spring Boot works on an opinionated view of the Spring platform being used by us and ensures that team can quickly start working on solving the actual business problem rather than spending time on the initial configurations and setup.

Spring Boot provides the following feature out of the box

    1. It simplifies Spring dependencies by taking the opinionated view ( we will discuss it in more details).
    2. Spring Boot provides a preconfigured set of technologies/framework to reduces error-prone configuration so we as a developer focused on building our business logic rather than thinking of project setup.
    3. You really don’t need those big XML configurations for your project.
    4. Embed Tomcat, Jetty or Undertow directly.
    5. Provide opinionated Maven POM to simplify your configuration

 

Using Spring Boot, it’s easy to manage and handle issues highlighted in the introduction section. .We are not required to manually search for compatible jars during upgrade,  Spring Boot will ensure that our application is upgraded to  the correct version (This is called working on application with minimum fuss)

Let’s take a look at a sample pom.xml for our web application to get an understanding of sample Spring Boot configuration

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.javadevjournal.demo</groupId>
    <artifactId>sample web application</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.7.RELEASE</version>
    </parent>
    <name>rWeb Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-hateoas</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>
</project>

Just pay close attention to <packaging> tag, Spring Boot provides flexibility to run our application as a jar and not forcing us to use war as required packaging type.

2. Better Dependency Management

Just check configuration closely and you won’t be finding any entry for all those Spring dependencies (like web MVC, core, AOP, ORM, Validation API etc.), you might have noticed similar entries spring-boot-starter-*, this is Spring Boot dependency management process. We have added spring-boot-starter-web to our pom.xml and Spring Boot will pull all required dependencies for Spring MVC application (no more manual configurations).

 

 

3. Auto Configurations

Auto Configuration is another interesting feature of Spring Boot this is why Spring Boot team say’s that it has opinions.These are some of work Spring Boot will do for you

  1. It will add all dependencies as highlighted in point 2.
  2. Auto Configurations indicates that Spring Boot has some reasonable defaults i.e based on the configurations Spring Boot will guess the type of application and will supply default implementations required to run your application in case we have not defined those in our application. in case you define these, Spring Boot will ensure that these defaults will be taken out of the context and let your custom configurations will take charge of application.
  3. To give a more clear picture, let’s say you have defined dependency for JPA and have not defined any database configurations, Spring Boot will automatically create required configurations for us. 

 

Read our article on to get the in-depth understanding of Spring Boot Auto Configurations.

 

 

3. Servlet Container

Do you recall that process of deploying your application on the Servlet container (Tomcat etc.), every time we make those small changes and require to deploy those into the app server to test our changes? Spring Boot provides support for embedded Servlet container and we are no longer require to deploy our application on app server (This can be run easily using standard main method) but at the same time we can access our application on the browser using http://<host>:<port>

Spring-boot-starter-web entry in our pom.xml will provide embedded servlet container for our web application, Apache Tomcat is the default servlet container provided by Spring Boot, however, Spring boot provides ways to use other servlet containers (all we have to add the required starter for this).

 

Read our post Building an Application with Spring Boot to start building your application with Spring Boot.

 

 

Summary

In this post, we get an understanding of the Spring Boot, we covered What is Spring Boot? and what are the Benefits of Spring Boot? We discussed different features of the Spring Boot. Spring Boot internally does a lot of things for us which seems to magical to us. In this series, we will be uncovering all these internal details of the Spring Boot.

Spring Boot Logging

Introduction to Spring Boot Logging

Logging is one of the important features of any enterprise application, in this post we will get an understanding of Spring Boot Logging mechanism along with few of configuration details.

 

Introduction 

Spring Boot comes with many ready to use features and Logging is one of those features, by default Spring Boot use Commons Logging for its internal logging but it also provides options to use/configure any other log mechanism.

If we are using Spring Boot Starters for our application, Logback will be used for logging by default unless we want to use any other logging API.

 

1.  Understand Log Output

Before we get into more details, let’s take a quick look at the default log out for the Spring Boot application to understand it more clearly.

2017-11-07 20:26:37.317  INFO 5388 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot[email protected]53404716: startup date [Tue Nov 07 20:26:34 PST 2017]; root of context hierarchy
2017-11-07 20:26:37.404  INFO 5388 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/],methods=[GET || POST]}" onto public java.lang.String com.umesh.rest.web.controller.DemoController.sayHello(javax.servlet.http.HttpServletRequest) throws java.io.IOException
2017-11-07 20:26:37.407  INFO 5388 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/demo/greeting],methods=[GET]}" onto public java.lang.String com.umesh.rest.web.controller.LoggingDemoController.sayHello()
2017-11-07 20:26:37.409  INFO 5388 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2017-11-07 20:26:37.410  INFO 5388 --- [  restartedMain] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)

There are certain things to understand above log output

  • Date and Time: First section indicates date and time of the log output. (e.g. 2017-11-07 20:26:37.317)
  • Log Level: Second main output indicated log level (e.g. INFO in our case).
  • Number as third output indicates process id (e.g. 5388)
  • — indicated separator
  • Output enclosed in [] indicates Thread name.
  • Last 2 output indicates Logger Name / Log Class name and logs message.

 

2.  Example

To understand how to configure and control Spring Boot Logging, let’s create a simple Controller with few log statements in it.


import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@Controller public class LoggingDemoController {
    
 private final Logger log = LoggerFactory.getLogger(this.getClass());
 
 @GetMapping("/demo/greeting") public String sayHello() {
  log.info("Info log statement for LoggingDemoController");
  log.warn("Warn log statement for LoggingDemoController");
  log.error("Error log statement for LoggingDemoController");
  return "greeting";
  
 }
 
}

On running above application by opening http://localhost:8080/demo/greeting, we can see following output in the console.

2017-11-07 20:43:41.566  INFO 5430 --- [io-10070-exec-4] c.u.r.w.c.LoggingDemoController          : Info log statement for LoggingDemoController
2017-11-07 20:43:41.567  WARN 5430 --- [io-10070-exec-4] c.u.r.w.c.LoggingDemoController          : Warn log statement for LoggingDemoController
2017-11-07 20:43:41.567 ERROR 5430 --- [io-10070-exec-4] c.u.r.w.c.LoggingDemoController          : Error log statement for LoggingDemoController

Spring Boot Logging API provides a number of features which help us to decouple out code

  • We are using SFL4J facade for our logging thus we are decoupled from underlying Logback API.
  • By using it, we are free to replace Logback with any other logging API without changing our code base.

 

3.  Log File Output

by default, Spring Boot Logging API will log output to the console and not to any file, for writing log output to a file, we can set logging.file or logging.path property in the application.properties file.

logging.file =/work/demo/log/loggingdemocontroller.log
//or
logging.path= /work/demo/log

Please note that if in case we use logging.path property, Spring Boot will write a file with a name spring.log to the specified directory.

 

4.  Setting Log Levels

Spring Boot provides an easy way to configure and set logging levels for your application.We can use application.properties file to configure the desired Logging level for our application by using ‘logging.level.*=LEVEL’. Let’s use our previous example to get an understanding of setting log level in our application. We will configure our log level to output only WARN and ERROR logs.

application.properties

logging.level.com.javadevjournal.rest= WARN

On running above application by opening http://localhost:8080/demo/greeting, we can see following output in the console.

2017-11-08 20:05:13.362  WARN 8647 --- [nio-8080-exec-1] c.j.r.w.c.LoggingDemoController          : Warn log statement for LoggingDemoController
2017-11-08 20:05:13.362 ERROR 8647 --- [nio-8080-exec-1] c.j.r.w.c.LoggingDemoController          : Error log statement for LoggingDemoController

Since we configured our log level to the WARN, Spring Boot Logging API will only output log statements for WARN and higher (in our case WARN and ERROR).

The root logger can be configured using logging.level.root.

 

5.  Configure Logback Through External File.

For most of the applications, Spring Boot Logging default configurations are more than sufficient, however, for large-scale enterprise applications have complex logging requirements and Spring Boot provide a way to configure it through the external XML file.

You can put logback.xml or logback-spring.xml file in the root of your classpath it will be picked up from there by Spring Boot. Please note that logback-spring.xml is preferred over the logback.xml file by Spring Boot.

here is a sample logback-spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <include resource="org/springframework/boot/logging/logback/base.xml"/>
    <logger name="com.javadevjournal.rest" level="WARN" additivity="false">
        <appender-ref ref="CONSOLE"/>
        <appender-ref ref="FILE"/>
    </logger>
</configuration>

If you want to get more understanding of the System properties which the LoggingSystem takes care of creating for us, please have a look at base.xml file inside spring-boot jar and especially the following line 

<property name="LOG_FILE" value="${LOG_FILE:-${LOG_PATH:-${LOG_TEMP:-${java.io.tmpdir:-/tmp}}}/spring.log}"/>

 

6. Spring Boot Profiles in Logging

Spring Profiling is an excellent concept which provides us the flexibility to define properties for the different environment without any code change. Spring Boot provides the same profile mechanism for the logback configuration by using the <springProfile> element. Let’s use an example to understand how you can define different logging level for DEV and Production environments using the same logback configuration.

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <include resource="org/springframework/boot/logging/logback/base.xml" />
    <springProfile name="dev">
        <logger name="com.javadevjournal.rest" level="DEBUG" additivity="false">
            <appender-ref ref="CONSOLE" />
        </logger>>
    </springProfile>
    <springProfile name="production">
        <logger name="com.javadevjournal.rest" level="WARN" additivity="false">
            <appender-ref ref="FILE" />
        </logger>
    </springProfile>
 </configuration>

Read Spring Profiles to get an understanding of how to use Spring Profiles feature for your application. 

 

7. Configure Log4j

Not all application want to use default logging configuration and it holds true for Spring Boot Logging mechanism, however, Spring Boot provides an easy way to use any other logging framework.In case you want to use Log4j2 for logging configuration, all you have to add the log4j2 starter in your application (no other complex configurations).

Please be aware that if If you are using the starters for your application, you need to exclude logback and then include log4j 2 instead.

Here is a sample configuration to use log4j for your application.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>

 

Summary 

In this post, we explored different features of the Spring Boot Logging API, we discussed what are the default configurations provided by Spring Boot along with options to configure or customize these options.

Logging is one of the main tool in the application development and with complex enterprise applications, logging requirement can become very complex with the time, however, Spring Boot Logging API provides all the tools to handle all these complex use cases with minimal configuration changes.

If you are starting with Spring Boot, please read Building an Application with Spring Boot to start your journey with Spring Boot

Log Incoming Requests In Spring

How to Log Incoming Requests In Spring

In this post, we will explore as of how to Log Incoming Requests In Spring. We will explore different options to accomplish it along with the build in feature provided by Spring.

 

1. Introduction

Having the ability to log incoming request in a web application is a very common requirement for modern web applications.In this article, we will be covering how to do it using Spring’s logging filter.

 

2. Dependency Management

In order to add required logging dependencies, we can add spring-core, for this article, we will be using Spring Boot which will handle dependency management for us. Checkout Building an Application with Spring Boot to learn about Spring Boot dependency management. We will add Spring Boot dependencies to start our web application.

<dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
</dependency>

 

3. Web Controller

In order to log incoming request, we need to have a Spring Controller in place, we will be using a simple controller for our post. Read  Creating a Web Application with Spring Boot to get an understanding of creating a web application using Spring Boot.

@RestController
public class LoggingDemoController {

    @GetMapping("/demo/greeting")
    public String sayHello(){
        return "Hello Stranger !!!";
    }
}

There is nothing special with this controller and it is simply returning "Hello Stranger !!! " to the client.

 

4. Custom Solutions

We will not get into details for this solution, but we can Spring provides interceptors to perform actions before and after web request.You can use HandlerInterceptor to create your custom implementation to log incoming request.

You have to be careful while using such approach as input stream will be marked as consumed the moment it is read for the first time.

We can also use Spring’s ContentCachingRequestWrapper to handle above issue by storing request stream in the cache but this needs a certain amount of work and customization.

 

5. Spring Built-In Request Logging

Spring comes with ready to use a feature which can log your request, all we are required to configure this ready to use solution. Spring comes with AbstractRequestLoggingFilter, that perform logging operations before and after a request is processed.

Before we get into implementation details, this filter requires a subclass to override the beforeRequest(HttpServletRequest, String) and afterRequest(HttpServletRequest, String) methods to perform the actual logging around the request.

Spring provides following 2 implementations for AbstractRequestLoggingFilter

  1. CommonsRequestLoggingFilter
  2. ServletContextRequestLoggingFilter

 

ServletContextRequestLoggingFilter Simple request logging filter that writes the request URI (and optionally the query string) to the ServletContext log.We are going to discuss CommonsRequestLoggingFilter in this post.

 

5.1 CommonsRequestLoggingFilter using Spring Boot

Spring Boot is the new way to create and run your Spring-powered applications, we can enable CommonsRequestLoggingFilter by simply registering it as a bean with our application.

@Bean
public CommonsRequestLoggingFilter requestLoggingFilter() {
    CommonsRequestLoggingFilter loggingFilter = new CommonsRequestLoggingFilter();
    loggingFilter.setIncludeClientInfo(true);
    loggingFilter.setIncludeQueryString(true);
    loggingFilter.setIncludePayload(true);
    loggingFilter.setIncludeHeaders(false);
    return loggingFilter;
}

In addition to above configuration, we need to make sure to set log level as DEBUG for CommonsRequestLoggingFilter either through application.properties or YAML

logging.level.org.springframework.web.filter.CommonsRequestLoggingFilter=DEBUG

Once these configurations are in place, you should be able to see a similar output in the console

2017-10-25 19:52:02.708 DEBUG 70034 --- [io-10070-exec-4] o.s.w.f.CommonsRequestLoggingFilter      : Before request [uri=/demo/greeting;client=0:0:0:0:0:0:0:1]
2017-10-25 19:52:02.791 DEBUG 70034 --- [io-10070-exec-4] o.s.w.f.CommonsRequestLoggingFilter      : After request [uri=/demo/greeting;client=0:0:0:0:0:0:0:1]

And voila, you have your requests are getting logged.

5.2 CommonsRequestLoggingFilter without Spring Boot

If you are not using Spring Boot, You can configure this by using traditional Filter.We have following options to configure this in our traditional web application

  1. Configure this Filter either through xml configuration or Java configuration with default values.
  2. Create a custom filter by extending CommonsRequestLoggingFilter to modify default behaviour.

 

5.2.1 CommonsRequestLoggingFilter using XML

If you want to use CommonsRequestLoggingFilter with no changes, you can simply configure it in your application configuration file as a filer

<filter>
    <filter-name>requestLoggingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CommonsRequestLoggingFilter</filter-class>
    <init-param>
        <param-name>includeClientInfo</param-name>
        <param-value>true</param-value>
    </init-param>
    <init-param>
        <param-name>includePayload</param-name>
        <param-value>true</param-value>
    </init-param>
    <init-param>
        <param-name>includeQueryString</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>
 
5.2.2 CommonsRequestLoggingFilter using Java Web Initializer

If you are not a fan of using XML configuration for your web application, Spring provides a way to configure it using WebApplicationInitializer.Please note that WebApplicationInitializer Interface to be implemented in Servlet 3.0+ environments in order to configure the ServletContext programmatically.

public class MyWebAppInitializer implements WebApplicationInitializer {

    @Override
    public void onStartup(ServletContext container) {
        XmlWebApplicationContext appContext = new XmlWebApplicationContext();
        appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");

        ServletRegistration.Dynamic dispatcher =
                container.addServlet("dispatcher", new DispatcherServlet(appContext));
        dispatcher.setLoadOnStartup(1);
        dispatcher.addMapping("/");

        container.addFilter("requestLoggingFilter", CommonsRequestLoggingFilter.class)
                .addMappingForServletNames(null, false, "dispatcher");
    }

}
5.2.3 Custom CommonsRequestLoggingFilter

If you want to customize behaviour of CommonsRequestLoggingFilter, you can always create your custom Filter by extending CommonsRequestLoggingFilter

public class CustomeRequestLoggingFilter extends CommonsRequestLoggingFilter {

    // custom code
}

You can use any of the above options to configure your custom Filter.

 

Summary

In this post, we explore as of how to Log Incoming Request in Spring.Spring comes with many hidden features which can always help us to avoid writing custom/duplicate code and CommonsRequestLoggingFilter is one of such hidden gem in Spring.

Building an Application with Spring Boot

Building an Application with Spring Boot

In this post, we will explore Building an Application with Spring Boot. We will cover different aspects of Spring Boot along with different options to build an application using Spring Boot.

 

1. Introduction

Spring Boot is an opinionated, convention over configuration.Spring Boot takes away most part of the project set up by taking an opinionated view of the Spring platform so that new and existing users can quickly get to the bits they need.Spring Boot makes it easy to create a Spring-powered enterprise application with minimum fuss. 

 

2. Spring Boot Features

Spring Boot provides the following feature out of the box

  1. It simplifies Spring dependencies by taking the opinionated view ( we will discuss it in more details).
  2. Spring Boot provides a preconfigured set of technologies/framework to reduces error-prone configuration so we as a developer focused on building our business logic rather than thinking of project setup.
  3. You really don’t need those big XML configurations for your project.
  4. Embed Tomcat, Jetty or Undertow directly.
  5. Provide opinionated Maven POM to simplify your configuration

 

3. Creating Spring Boot Project

One of the main challenges to starting up a new project is the initial setup for the project. We need to take a call about the different directory structure and also need to make sure we are following all the industry standards.If you are using Maven, you might already be using Maven startup artefact which helps us to do those initial setups more quickly.

Spring Initializr is another great tool to quickly start Spring Boot projects. Spring Initializr is a web application that generates Spring Boot projects. Keep in mind that it will only generate project structure and not any code for you based on your preference (Maven or Gradle). If you are starting your project, my recommendation is to start with Spring Initializr.

There are multiple ways to use Spring Boot Initializr to generate project structure for you.

  1. Using  Spring Initializr Web Interface.
  2. Use Spring Boot CLI tool.
  3. Use your IDE

 

3.1 Using Spring Initializer Web Interface

This is the simplest way to generate project structure for your application.Open Spring Initializr Web interface your browser and you will be presented with a wizard to start your configurations.

 Building an Application with Spring Boot

You are required to fill some information in the web interface to start with

  1. What kind of project you want to generate (Maven or Gradle)
  2. What is your preferred language (Apart from Java you will get an option for Kotlin and Groovy)
  3. Spring Boot Version
  4. Standard project group and artefact details.
  5. Dependencies.

Dependencies is an interesting feature in the web interface, based on your selected Dependencies, web interface will automatically add Spring Boot Starter dependencies in the generated pom.xml file.In case you want a more control on the generated project structure or not sure what all dependencies you want to add to your project, click on the “Switch to the full version”.

Spring Boot

 

With the full version, you have the option to select Java version, packaging mode (maybe .war for traditional deployment) along with an option to select dependencies for your project. Once you click on “Generate Project” button, Spring Initializr will generate project you will be given a zip to download. You can import the unzipped project as a simple Maven/ Gradle based project in your IDE.

I will not be covering details as to how you can import this in your IDE. Please refer to relevant IDE document for more details.

 

3.2 Using Spring Boot CLI

We can also use Spring Boot CLI to generate structure for your project, once you have installed CLI, open command prompt and type spring. If CLI is installed correctly, you should be seeing the very similar output on typing spring.


localhost:~ javadevjournal$ spring
usage: spring [--help] [--version]
       [<args>]

Available commands are:

  run [options]  [--] [args]
    Run a spring groovy script

We can use init as an additional parameter with spring to create a new project. Spring Boot CLI will internally be going to use start.spring.io to generate project structure for you.

localhost:~ javadevjournal$ spring init --dependencies=web springboot-demo-project
Using service at https://start.spring.io
Project extracted to '/Users/umesh/springboot-demo-project'

It created springboot-demo-project directory with a maven based project using spring-boot-starter-web. This will create a project with the same default setting as available on the start.spring.io web interface. We can pass different parameters to customize project generation.

Let’s say we want to generate our project based on Java 1.7, we can pass --java-version=1.8 as an additional parameter to Spring Boot CLI.

spring init --java-version=1.7 --dependencies=web springboot-demo-project

When you will run above command, it will automatically set java-version in the generated pom.xml file as 1.7.

<properties>
    <java.version>1.7</java.version>
</properties>

If you are not sure what are the capabilities of the Spring init service, run init command with --list flag.

 spring init --list

 

4. Peek Inside pom.xml

Let’s start looking into pom.xml file to understand Spring Boot configurations in more detail. I will be covering only Spring Boot related changes in pom.xml. Here is the pom.xml file from our sample project.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.umeshawasthi</groupId>
  <artifactId>ems</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>ems</name>
  <description>Employee Management System outline Spring Boot Features</description>

  <parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
     <version>1.5.4.RELEASE</version>
     <relativePath/> <!-- lookup parent from repository -->
  </parent>
   <!-- project properties repository -->
  <dependencies>
     <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
     </dependency>

     <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <scope>provided</scope>
     </dependency>
        <!-- Spring boot test depedency -->
  </dependencies>
</project>

One of the main features of Spring Boot is the “Starters”, they are an easy way to add required dependencies (jars) in your classpath. When using Spring Boot, we don’t have to add jar/dependencies in your classpath (In case a starter is not available, you might have to add these dependencies in the pom.xml or can create your own custom starter). We just need to add correct “Starters” in our pom.xml file and Spring Boot will make sure to add those dependencies automatically.

 

5. Application Entry Point

@SpringBootApplication
public class EmsApplication {

  public static void main(String[] args) {
    
     SpringApplication.run(EmsApplication.class, args);
  }
}
5.1 @SpringBootApplication Annotation

Our main class is using @SpringBootApplication annotation. @SpringBootApplication is equivalent to using @Configuration, @EnableAutoConfiguration and @ComponentScan with their default values.If you are starting your project, it’s recommended to use annotation. Using @SpringBootApplication in your main class is equivalent to following 3 annotations

  1. @Configuration as a source of bean definitions.
  2. @EnableAutoConfiguration It gives Spring Boot an idea as to how you want to configure your application.
  3. @ComponentScan to automatically pick up all Spring components, including @Configuration classes.

 

5.2 Main Method

Another interesting feature of our main class is the main method. This is a standard method that will follow standard Java workflow. Our main class will pass on control to Spring Boot SpringApplication class. SpringApplication Class run method will be used to the BootStrap application. We will be taking a more deep look into the SpringApplication later section.

 

6. Hello World Controller

package com.javadevjournal.demo.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;


@RestController
public class HelloWorldController {

   @RequestMapping("/")
   public String helloWorld(){
       return "Hello World!!";
   }
}

There is nothing special in our Controller. It’s a standard Spring-MVC controller with standard Spring MVC annotations.

 

6. Running Application

It’s time to run our first Spring Boot powered application. We have multiple ways to run our Spring Boot application.

  1. If you are using IDE, you can use IDE to run your application.
  2. We can use mvn spring-boot:run command from the root directory to start our first Spring Boot application.
 .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.4.RELEASE)

2017-07-08 15:49:50.319  INFO 1238 --- [           main] com.javadevjournal.demo.EmsApplication   : Starting EmsApplication on localhost with

Open up the browser of your choice and type http://localhost:8080, you should see “Hello World” as an output.

 

Summary 

Spring Boot provides a good boost to the Spring-based applications. In this post, we learned about different options of Building an Application with Spring Boot.Setting up a new project is always a challenging task and we need to make sure to manage all dependencies but with Spring Boot, it was really easy and we able to run our first web application with only new lines of code without thinking much about the required dependencies or the deployment.

Custom Banners in Spring Boot

How to Use Custom Banners in Spring Boot

When we start our Spring Boot application, it comes up with a default Banner, in this post we will discuss how to use Custom Banners in Spring Boot application.

 

Introduction

It’s highly likely that you want to release your own product/application based on the Spring Boot and want to display your own custom banner in place of default Spring Boot Banner.By default Spring

By default, Spring Boot application will display the following banner on startup

.   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.7.RELEASE)<

 

1. Creating Custom Banner

In order to start, we need to create a custom banner which will be used to display on the application startup time. I will be using  Spring Boot Banner Generator to upload an image for generating ANSI character in the plain text.You can always generate it manually if you want :).

For this tutorial, I will be using  Spring Logo logo from Spring IO site. 

 

2. Using The Custom Banner

In the above section, we have created a custom banner and it’s time to start using this custom banner.We will be creating a file banner.txt under the src/main/resources folder and will paste content in this file.

Spring Boot by default will pick content from the banner.txt file, in case it will find a banner.txt in our project classpath (resources folder of our application), it will pick custom banner content and will display it on the startup.

In case we want Spring Boot to pick banner content from other location and not from the default banner.txt, we can customize that by setting banner.location to the location of such a file

banner.location=classpath:/path/to/banner/custom-banner.txt

Here is the output when we run our application with new content in banner.txt file

Custom Banners in Spring Boot
Custom Banners in Spring Boot

 

2.1 Using Image for Custom Banner

We can even use the image as a custom banner for our Spring Boot application, We can add banner.gif, banner.jpg or banner.png image file to your classpath and Spring Boot will automatically pick this image as a startup banner. Please note that we need to name these banner images as a banner.extension (e.g. banner.jpg). 

You can use banner.image.location property to set a custom location for our banner image in the application.properties file, we can also use some additional properties to customize our banner


banner.image.location=classpath:banner.gif # Banner image file location (jpg/png can also be used).
banner.image.width= # Width of the banner image in chars (default 76)
banner.image.height= # Height of the banner image in chars (default based on image height)
banner.image.margin= # Left hand image margin in chars (default 2)
banner.image.invert= # If images should be inverted for dark terminal themes (default false)

Images will be converted into an ASCII art representation before getting printed on the startup which can add a lot of time on startup in case we have a complex image.It is recommended to use text format for a Custom Banners in Spring Boot.

If you want you can use SpringApplication.setBanner(… ) method to set custom banner programmatically but in my opinion, this is not preferred way and you need to implement your own printBanner() provided under org.springframework.boot.Banner interface. 

 

Summary 

In this short post, we learned how to use a Custom Banners in Spring Boot. We explored the option to create a custom banner using a banner.txt file or placing your custom image in your classpath.

Spring Boot Starters

Introduction to Spring Boot Starters

In this post, we will introduce Spring Boot Starters to you and will discuss what are the benefits and advantages of Spring Boot Starters.

 

Introduction

Before starting any project be it a small project or an enterprise level application, one of the critical aspects is dependency management, doing it manually for a small application is not a hard job but when it comes to complex applications, managing all project dependencies manually is not ideal and prone to many issues as well wasting of the time which can be used in some other important aspects of the project.

Ond of the fundamental principle behind Spring Boot is to address similar issues.Spring Boot Starters are a set of convenient dependency descriptors which can be easily included in any level of application.These starters work as a  bootstrapping process for the Spring related technologies, we no longer need to worry about the dependencies and they will be automatically managed by Spring Boot Starters.      

The starters contain a lot of the dependencies that you need to get a project up and running quickly and with a consistent, supported a set of managed transitive dependencies.

 

1. Why Do We Need Starters?

When we start with the Spring Boot, one of the fundamental questions which come to our mind is why do we need Spring Boot Starters? or how these starters will help me in my application?

As mentioned earlier, these starters work to bootstrap your application, all we need is to include correct starter in our application and Spring Boot will ensure that all dependencies required for the chosen starter are in your classpath.

To understand it more clearly, let’s take an example that we want to build a simple Spring Web-MVC application, in order to start, we need to think of the following points before actually starting working on our web application code.

  • Correct Spring MVC Dependencies.
  • Required dependencies for Web technologies (e.g We want to use Thymeleaf)
  • We need to make sure that all these dependencies are compatible

 

With Spring Boot Starters, bootstrapping our Spring-MVC web application is really straightforward, We need to include spring-boot-starter-web starter in our pom.xml,

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Above entry in pom.xml will ensure that all required dependencies should be in your classpath and we are all set to start working on our web application. 

Currently, there are around 50+  starters offered by Spring Boot excluding third party starters.For the updated list of starters, please refer to  Spring Boot Starter

In this section, I will be covering some of the commonly used starters.

 

2. Web Starter

This is one of the most commonly used Spring Boot Starter, This starter will ensure that all required dependencies to create Spring Web application (including REST) are included in your classpath, it will also add tomcat-starter as default server to run our web application. To include Web Starter in our application, add following entry in pom.xml.

<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Now we can create our Spring-MVC Controller

 @RestController
    public class SampleController {

        @RequestMapping("/greeting")
        String hello() {
            return "HelloWorld!";
        }
    }

If you run your application and access,http://localhost:8080/greetings you should be able to get “Hello Word” as the response.We created a REST controller with minimal code.

 

3. Data JPA Starter

Most of the application will need some persistence mechanism and JPA is established standard for the persistence, Spring Boot Starters comes with JPA Starters, You no longer have to configure those JPA dependencies manually, this can be easily achieved by adding JPA Starter in your application.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
</dependency>

Spring JPA Starter provides automatic support for H2, Derby and Hsqldb.Let’s have a look at how easy is to create a sample JPA application using JPA starter.

@Entity
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String firstName;
    private String lastName;

    protected User() {
    }

    public User(String firstName, String lastName) {
        //this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", firstName='" + firstName + '\'' +
                ", lastName='" + lastName + '\'' +
                '}';
    }
}

Here is our UserRepository

public interface UserRepository extends CrudRepository<User,Long> {
    List<User> findUserByLastName(String lastName);
}

Time to test our code, here is the JUnit test

@RunWith(SpringRunner.class)
@SpringBootTest
public class JpademoApplicationTests {

   @Autowired
   UserRepository userRepository;

   @Test
   public void contextLoads() {

        User user = userRepository.save(new User("Demo","User"));
        User searchUser= userRepository.findOne(user.getId());

        assertNotNull(searchUser);
        assertEquals(user.getFirstName(),searchUser.getFirstName());

   }

}

As we saw in above code, you longer need to specify those database configurations or extra DB configurations, by adding JPA starter, many features were available to us out of the box with no need to configure or code. 

You can always modify/customize these configurations if needed.

 

4. Mail Starter

Sending email from our application is very common tasks and every application these days require to send emails from the system.Spring Boot Mail starter provides an easy way to handle this feature by hiding all complexities. 

We can enable email support by simply adding mail starter in our application.

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

I am using Mailgun as my SMTP Server, here are the SMTP details added to my application.properties file

spring.mail.host=smtp.mailgun.org
[email protected]
spring.mail.password=mypassword
spring.mail.properties.mail.transport.protocol=smtp
spring.mail.properties.mail.smtp.port=587
spring.mail.properties.mail.smtp.auth=true

 

Our EmailService class responsible for sending emails 

@Component
public class JavaEmailService {

    private JavaMailSender mailSender;

    public JavaEmailService(JavaMailSender mailSender) {
        this.mailSender = mailSender;
    }

    public void sendEmail(){
        MimeMessagePreparator messagePreparator = mimeMessage -> {

            MimeMessageHelper helper = new MimeMessageHelper(mimeMessage);
            helper.setFrom("[email protected]");
            helper.setTo("[email protected]");
            helper.setSubject("Sample mail subject");
            helper.setText("Test Email");
        };

        mailSender.send(messagePreparator);
    }
}

We have used  JavaMailSender provided by Spring for email. Time to test the code. Here is the JUnit test

@RunWith(SpringRunner.class)
@SpringBootTest
public class EmailTest {

    @Autowired
    JavaEmailService javaEmailService;

    @Test
    public void sendEmail(){

        javaEmailService.sendEmail();

    }
}

Again, a minimal code and configuration were needed to send a simple email, Spring Boot Mail Starter ensured that all required tools are already in place to quickly start working on the real problem.

Notice that we’re using  JavaMailSender in JavaEmailService bean – the bean was automatically created by Spring Boot.

 

5. Test Starter

We normally use Junit, Mockito or Spring Test for testing our application.We can easily include all these libraries in our application by adding Spring Boot Test starter.

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-test</artifactId>
</dependency>

Spring Boot will automatically find our correct version to be used for our application test. Here is a sample JUnit test

@RunWith(SpringRunner.class)
@SpringBootTest
public class EmailTest {

    @Autowired
    JavaEmailService javaEmailService;

    @Test
    public void sendEmail(){

        javaEmailService.sendEmail();

    }
}

Apart from these starters, below are other frequently used Spring Boot Starters

  • spring-boot-starter-security 
  • spring-boot-starter-web-services
  • spring-boot-starter-integration
  • spring-boot-starter-validation
  • spring-boot-starter-actuator

As mentioned earlier, please refer to  Spring Boot Starter for up to date list of the starters provided by Spring Boot.

Summary

This article provides an Introduction to Spring Boot Starters, we discussed as to why do we need these starters and how they can help us to quickly bootstrap our application. We explored some of the most commonly used Spring Boot Starters.

Suggested reading

Building an Application with Spring Boot

Spring Profiles

Introduction to Spring Profiles Using Spring Boot

In this post, we will be exploring Spring Profiles using Spring Boot and will see how we can use it efficiently in our project.

 

Introduction

Spring Profiles provides a powerful and easy way to control code and configuration based on the environment. Using Spring Profiles it’s possible to segregate parts of our application and make it only available in certain environments. We can use @Profile annotation to limit the availability of any @Component  or @Configuration.

 

1. Use @Profile Annotation

Main entry point for the Spring Profile is @Profile annotation which can be used to group things together. Let’s take a simple example for a Database connection bean where we want to make sure that certain DB connection should be active only in DEV mode but not in production or QA / Staging. We can use @Profile annotation to achieve this.

@Service
@Profile("development")
public class DevDBConnection implements  DatabaseService {
    
    @Override
    public void getDBConnection() {
        System.out.println("DEV DB connection established");
    }
}

Since we annotated DevDBConnection bean with “development” profile, it will only be available in the Spring container if development profile is active, in other words, if development profile is not active, this bean will not be available/active.  

Default profile used by Spring profile is the default. All the beans with no profile annotation are specified belongs to the default profile. We can also set default profile in Spring Boot by  @Profile("default") or @Profile({"default","development"}).

 

2. Use @Profile Annotation

Spring Boot provides multiple ways to active profile. We can pass profile information through the command line or use application.properties, Spring Boot also provide a way to set profile programmatically.

2.1 Using Command Line

We can pass profile information to Spring Boot using the switch through command prompt —spring.profiles.active=development,staging

 
2.2 Using Property File

We can use standard Spring environment property spring.profiles.active property in our application.properties or application.yaml to specify active profiles.

spring.profiles.active=development,staging
 
2.3 Programmatically setting profile

We can programmatically set active profile by calling setAdditionalProfiles(...) method provided by SpringApplication class

SpringApplication app = new SpringApplication(Application.class);
app.setAdditionalProfiles("development","production");

Take a note that spring.profiles.active property follows same ordering rule as followed by other properties defined by Spring Boot. Highest property source will overwrite any other property defined in the hierarchy. Please refer to Spring Boot documentation to understand how Spring Boot read these properties.

3. Profile Specific Configurations

One of the most interesting and powerful features provided by Spring Boot is the ability to define profile specific application.properties file and active these by main application.properties file.

To use profile specific configuration files, we need to the naming convention of application-{profile}.properties where profile defines the name of the intended profile. Profile specific files will be loaded from the same location as application.properties file, also be aware that profile specific properties will override properties defined in the default application.properties irrespective of whether the profile-specific files are inside or outside your packaged jar.

To understand it completely, let’s take the same example of Database configuration where we want to define different DB configurations for Development and Production.To achieve this using configuration files, we will define 2 configuration file namely application-production.properties and application-development.properties. 

application-production.properties

db.url=jdbc:oracle:thin:@<host>:1521:<sid>
db.driver=oracle.jdbc.driver.OracleDriver
db.username=<username>
db.password=<password>
db.tableprefix= 

application-development.properties

db.url=jdbc:hsqldb:file:configurations
db.driver=org.hsqldb.jdbcDriver
db.username=sa
db.password=
db.tableprefix=

In above example we used HSQL for Development while we want to use Oracle for production and based on the active profile, we can easily switch DB configurations.

Please read @ConfigurationProperties in Spring Boot to understand how Spring Boot Configuration works

4. Complete Example

Here is a complete example to understand how Spring Boot Profile work.

DataBase Service

public interface DatabaseService {

    void getDBConnection();
}

Development Profile

@Service
@Profile("development")
public class DevDBConnection implements  DatabaseService {

    @Override
    public void getDBConnection() {
        System.out.println("DEV DB connection established");
    }
}

Production Profile

@Service
@Profile("production")
public class ProdDBConnection implements DatabaseService {

    @Override
    public void getDBConnection() {
        
        System.out.println("Product DB connection establish");
    }
}

Spring Boot Runner

@SpringBootApplication
public class SpringbootTutorialsApplication implements CommandLineRunner{

   @Autowired
    DatabaseService databaseService;

    public static void main(String[] args) {

      SpringApplication.run(SpringbootTutorialsApplication.class, args);
   }

    /**
     * Callback used to run the bean.
     *
     * @param args incoming main method arguments
     * @throws Exception on error
     */
    @Override
    public void run(String... args) throws Exception {
        databaseService.getDBConnection();
    }
}

output

if you run above example with development profile as active profile, we will have the following output

DEV DB connection established

5. Conclusion

In this post, we covered Spring Profile features, we learned how to use Spring Profile in Spring Boot using different options.Spring profile is a powerful way enable right profile in our application, ability to define profile specific configuration files in Spring Boot gives a lot of flexibility to manage our applications.

Spring Boot Web Application Configuration

Spring Boot Web Application Configuration

In this short post, we will cover some of the interesting aspects of the Spring Boot web application configuration.We will be covering some of the most commonly used configurations for a web application.

 

1. Introduction

Spring Boot comes with build in intelligence which makes it easy to create the web or standalone application.Spring Boot can do a lot of things for us without even writing a single line of code for our web application and we will be covering few of those configurations.

 

2. HTTP Port

One of the common configuration for a web application is the HTTP port number, we can easily configure HTTP port number for our application using following options

  • Using application.properties file
  • By YAML based configuration
  • Setting HTTP port number programmatically.

 

2.1 Setting HTTP Port by Configuration

For properties file

server.port=9001

For YAML

server:
        port: 8083

 

2.2 Setting HTTP Port by Programmatically

We can also set HTTP port programmatically in Spring Boot

@Component
public class CustomConfiguration implements EmbeddedServletContainerCustomizer {
    /**
     * Customize the specified {@link ConfigurableEmbeddedServletContainer}.
     *
     * @param container the container to customize
     */
    @Override
    public void customize(ConfigurableEmbeddedServletContainer container) {
        container.setPort(9001);
    }
}

 

3. Context Path

Default context for a Spring Boot web application is "/", Spring Boot provides the option to set context either through configuration or programmatically.

 

3.1 Setting Context by Configuration

For properties file

server.contextPath=/javadevjournal

For YAML

server:
        contextPath:/javadevjournal

 

3.2 Setting Context by Programmatically

We can also set context programmatically in Spring Boot

@Component
public class CustomConfiguration implements EmbeddedServletContainerCustomizer {
    /**
     * Customize the specified {@link ConfigurableEmbeddedServletContainer}.
     *
     * @param container the container to customize
     */
    @Override
    public void customize(ConfigurableEmbeddedServletContainer container) {
        container.setPort(9001);
        container.setContextPath("/javadevjournal");
    }
}

 

4. BasicErrorController

If you are working with Spring Boot application, you should be familiar with While Label Error Page. Spring Boot automatically register BasciErrorController bean if we do not specify our own custom bean.We can customize this by extending ErrorController.

@Controller
public class CustomErrorController implements ErrorController {

    private static final String PATH = "/error";


    @RequestMapping(value = PATH)
    public String error() {
        return "errorHandling";
    }

    /**
     * Returns the path of the error page.
     *
     * @return the error path
     */
    @Override
    public String getErrorPath() {
        return PATH;
    }
}

5. Custom Error Pages

Spring Boot provides a way to use your own custom error pages based on the error code. We need to add error code based pages under the /error directory and Spring Boot will use correct page based on the error code.

We can use either static HTML or can use a template to build our custom error pages. The name of the file should be the exact status code or a series mask.

We can use a similar structure to organize our templates.

src/
 +- main/
          +- java/
          |      + <source code>
          +- resources/
                  +- public/
                          +- error/
                           |     +- 404.html
                           +- <other public assets>

 

src/
 +- main/
          +- java/
          |      + <source code>
          +- resources/
                  +- public/
                          +- error/
                           |     +- 5xx.html
                           +- <other public assets>

 

6. Configure Logging

Spring Boot has no required dependencies for the logging (except common logging API). Spring Boot internally use LoggingSystem abstraction that attempts to configure logging based on the content of the classpath.

We can fine tune log out in Spring Boot application by setting log level in the application.properties file using logging.level as a predefined prefix

logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR

 

We can use different logging framework (Logback, Log4j2) in Spring Boot application.

 

Summary

In this post, we covered  Spring Boot Web Application Configuration which is required for setting up your web application correctly or as per your need.For more details, you can always refer to Spring Boot documentation.

Internationalization in Spring Boot

Introduction to Internationalization in Spring Boot

In this short post, we will explore how to add Internationalization in Spring Boot application.

1. Introduction

Spring Boot provides a number of build in features which help us to start application development quickly. Spring Boot provides ResourceBundleMessageSource which is a foundation to the internationalization provided by Spring as part of the Spring Boot.

We will be using thymeleaf as our front end templating engine.We can enable thymeleaf in Spring Boot application by using spring-boot-starter-thymeleaf.

 
<dependency>
   <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

 

2. Application Structure

We will be working with a Maven based Spring Boot application, here is the structure for our internationalization. (it will remain same for Gradle based project). Spring Boot application by default will look for internationalization key and values under /src/main/resources folder.

src/
|--  main/
      |--    resources/
               |--   messages.properties
               |--   messages_de.properties
               |--   messages_xx.properties

 

Default locale file will name as messages.properties and files for other locales will havemessages_xx.properties a format where xx is the locale code. In our case, we have another message file containing German data.

Keys which will be used for internationalization will be same in all the message_xx.properties file and only values will be different based on the locale.

If a key does not exist in a certain requested locale, then the application will fall back to the default locale value. 

Below is our sample message.properties file

Default

welcome.message=Welcome to Demo Application
language.change=Change Language
lang.eng=English
lang.de= German

messages_DE.properties

welcome.message=Willkommen bei der Demo-Bewerbung
change.language=Sprache ändern
lang.eng=Englisch
lang.de= Deutsche

 

3. LocaleResolver

LocalResolver is required to correctly determine which local is currently being used. LocalResolver interface allows for implementations based on a request, session, cookies, etc. The default implementation is AcceptHeaderLocaleResolver. We will be using session based LocalResolver in our sample code. Please read LocaleResolver for more details.

@Bean
public LocaleResolver localeResolver(){
       SessionLocaleResolver localeResolver = new SessionLocaleResolver();
       localeResolver.setDefaultLocale(Locale.US);
       return  localeResolver;
   }

 

4.LocaleChangeInterceptor

We need to configure an interceptor which allows for changing the current locale on every request, via a configurable request parameter 

@Bean
public LocaleChangeInterceptor localeChangeInterceptor() {
    LocaleChangeInterceptor localeChangeInterceptor = new LocaleChangeInterceptor();
    localeChangeInterceptor.setParamName("language");
    return localeChangeInterceptor;
}

default parameter name used by LocalCangeInterceptor is  “locale” but we will be using “language” as the request parameter.

 

We need to add our LocaleChangeInterceptor with Spring Boot so as this can be picked correctly by Spring Boot. In order to register this bean with Spring Boot, we need to override addInterceptor() method in our Configuration class.

@Override
public void addInterceptors(InterceptorRegistry registry){
    registry.addInterceptor(localeChangeInterceptor());
}

5. Controller 

In order to see this in action, we need a controller which will be used to serve a welcome page to see Spring Boot internationalization in action.

@Controller
public class WelcomeController {

    @RequestMapping("/")
    public String hello() {
        return "welcome";
    }
}

 

Above Controller will be come in to picture when we open our application home page (in our case it is http://localhost:8080). It will pick welcome.html template located at src/main/resources/templates.

 

6. UI / HTML

Here is our sample HTML 

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<body>

    <h1 th:text="#{welcome.message}"></h1>

    <span th:text="#{lang.change}"></span>:
    <select id="locales">
        <option value=""></option>
        <option value="en" th:text="#{lang.eng}"></option>
        <option value="de" th:text="#{lang.de}"></option>
    </select>

</body>
</html>

 

7. Demo Application

If we run our Spring Boot application using main class and open http://localhost:8080

@SpringBootApplication
public class JavadevspringbootApplication extends WebMvcConfigurerAdapter {

   public static void main(String[] args) {
      SpringApplication.run(JavadevspringbootApplication.class, args);
   }

   @Bean
   public LocaleResolver localeResolver(){
        SessionLocaleResolver localeResolver = new SessionLocaleResolver();
        localeResolver.setDefaultLocale(Locale.US);
        return  localeResolver;
    }

    @Bean
    public LocaleChangeInterceptor localeChangeInterceptor() {
        LocaleChangeInterceptor localeChangeInterceptor = new LocaleChangeInterceptor();
        localeChangeInterceptor.setParamName("lang");
        return localeChangeInterceptor;
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry){
        registry.addInterceptor(localeChangeInterceptor());
    }
}

We will get following HTML Page

Internationalization in Spring Boot
Internationalization in Spring Boot

 

On changing the URL by adding language in the URL (http://localhost:8080/?language=de), we will get German version of the site

Internationalization in Spring Boot
Internationalization in Spring Boot

 

7. Summary

In this post, we learned how to use Internationalization in Spring Boot.We get an understanding about Spring Boot build in support for Internationalization.

Creating a Web Application with Spring Boot

Creating a Web Application with Spring Boot

In this post, we will explore details of Creating a Web Application with Spring Boot. We will explore how Spring Boot can help you to accelerate your application development.We will be building a simple web application with Spring Boot and add some useful services to it.

 

1. Introduction

One of the main challenges to starting up a new project is an initial setup for the project. We need to take a call about the different directory structure and also need to make sure we are following all the industry standards.For creating a web application with Spring Boot, we need following tools

  • Our preferred IDE (I will be using IntelliJ) 
  • Maven
  • JDK 1.8+

 

 

2. Creating Project Structure

There are multiple ways to use Spring Boot Initializr to generate project structure for you.

  1. Using  Spring Initializr Web Interface.
  2. Use Spring Boot CLI tool.
  3. Use your IDE

For the simplicity of this post, we are using Spring Initializer web interface to generate project Structure.

Spring Initializr Web interface your browser and you will be presented with a wizard to start your configurations.

Spring Initializr

You are required to fill some information in the web interface to start with

 

  1. What kind of project you want to generate (Maven or Gradle)
  2. What is your preferred language (Apart from Java you will get an option for Kotlin and Groovy)?
  3. Spring Boot Version
  4. Standard project group and artifact details.
  5. Dependencies.

Dependencies is an interesting feature in the web interface, based on your selected Dependencies, web interface will automatically add Spring Boot Starter dependencies in the generated pom.xml file.In case you want a more control on the generated project structure or not sure what all dependencies you want to add to your project, click on the “Switch to the full version”. 

We will be using The Web and Thymeleaf (For UI) for this post.

 

3. Project Structure

Spring Boot does not require any specific code layout or structure.We can always follow some of the best practices suggested by Spring Boot team, however, final structure will be driven by your project requirement.

 

Here is the layout of our sample application

Project Structure

 

 

4. Pom.xml

Let’s start looking into pom.xml file to understand Spring Boot configurations in more detail. I will be covering only Spring Boot related changes in pom.xml. Here is the pom.xml file from our sample project.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>

   <groupId>com.javadevjournal</groupId>
   <artifactId>javadevspringboot</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>war</packaging>

   <name>javadevspringboot</name>
   <description>Java Dev Journal project for Spring Boot</description>

   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>1.5.4.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>

   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-thymeleaf</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-tomcat</artifactId>
         <scope>provided</scope>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>

</project>

One of the main features of Spring Boot is the “Starters”, they are an easy way to add required dependencies (jars) in our class path. When using Spring Boot, we don’t have to add jar/dependencies in our class path (In case a starter is not available, you might have to add these dependencies in the pom.xml or can create your own custom starter). We just need to add correct “Starters” in our pom.xml file and Spring Boot will make sure to add those dependencies automatically.

 

5. Main Application

Here is our main Spring Boot application class, this is a Spring Configuration class. The annotation @SpringBootApplication enables the Spring Context and all the startup magic of Spring Boot.

 

@SpringBootApplication
public class WebApplication extends WebMvcConfigurerAdapter {

   public static void main(String[] args) {
      SpringApplication.run(WebApplication.class, args);
   }
}

 

5. 1 @SpringBootApplication Annotation

@SpringBootApplication annotation. @SpringBootApplication is equivalent to using @Configuration, @EnableAutoConfiguration and @ComponentScan with their default values.If you are starting your project, it’s recommended to use annotation.

 

Using @SpringBootApplication in your main class is equivalent to following 3 annotations

 

  • @Configuration as a source of bean definitions
  • @EnableAutoConfiguration It gives Spring Boot an idea as to how you want to configure your application.
  • @ComponentScan to automatically pick up all Spring components, including @Configuration classes

 

5. 2 Main Method

Another interesting feature of our main class is the main method. This is a standard method that will follow standard Java workflow. Our main class will pass on control to Spring Boot SpringApplication class.

SpringApplication Class run method will be used to BootStrap an application.

 

6. Welcome Controller

Last part of our setup, we will create a welcome controller which will be responsible to handles GET requests for /greeting by returning the name of a View, in this case, “welcome”. A View is responsible for rendering the HTML content.

 

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;


@Controller
public class WelcomeController {

    @RequestMapping("/welcome")
    public String welcome() {

        return "welcome";
    }
}

This is a very simple controller but has covered a lot of points in our setup.

  • @Controller annotation indicates that an annotated class is a "Controller" (e.g. a web controller).
  • @RequestMapping annotation ensures that HTTP requests to /welcome are mapped to the welcome() method.
  • We have not specified any method to the @RequestMapping annotation as default maps all HTTP operations by default.
  • As we are using Thymeleaf for view technology and returning “welcome” from welcome() method, Thymeleaf parses the template welcome.html and produce the output.

 

6. 1 UI Template 

Here is our simple Thymeleaf HTML template.

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>Getting Started: Serving Web Content</title>

</head>
<body>
Hello and Welcome to our Web Application
</body>
</html>

While using Thymeleaf as our template engine, Spring Boot will look for resources by surrounding the view name with a prefix and suffix (externalized to spring.thymeleaf.prefix and spring.thymeleaf.suffix, defaults ‘classpath:/templates/’ and ‘.html’ respectively).

 

 

7. Run Application

We are done with our simple web application, it’s time to run our application. Although it is possible to package this service as a traditional WAR file for deployment to an external application server, the simpler approach demonstrated is to create a standalone application. To run our application from IDE, We need to run our web application as a standalone java application.

  • With Maven, we can run the application using mvn spring-boot:run command.
  • we can build the JAR file with mvn clean package command and run jar by using java -jar target/demo-app-0.1.0.jar.

Now the site is up and running, visit,http://localhost:8080/welcome and if everything is in place, you should have following output on your web browser.

"Hello and Welcome to our Web Application"

 

8. Summary

In this post, we learned Creating a Web Application with Spring Boot. Spring Boot comes with many builds in feature to create and run web application more quickly and with minimal efforts.