Spring Boot Starter Parent

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In this article, we are going to understand the Spring Boot Starter Parent. Spring Boot provides the parent POM for a quick and easy Spring Boot development. 

 

Introduction

Spring Boot starter parent is a convenient and easy way for dependency management. With each release, Spring Boot provides a curated list of dependencies that it supports. While working on the Spring Boot application, you may not need to provide the version number for the dependencies as these are automatically taken care by Spring Boot. This article takes a deeper look at the starter parent and some of its benefits. 

 

1. Spring Boot Starter Parent

When you create a Spring Boot project either through Spring Initializr or using IDE, typically you may have seen following entry in the pom.xml file:

<parent>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-parent</artifactId>
	<version>2.1.1.RELEASE</version>
</parent>

By setting the spring-boot-starter-parentas the parent, you are automatically adding following features to you Spring Boot application:

  1. Dependency management – Spring Boot automatically takes care of the version for you.
  2. Sensible Defaults
    1. Default Java version
    2. Source encoding
    3. Resource filtering etc.
  3. Plugin management

 

1.1 Starter Parents Internal

Spring Boot starter parent defines spring-boot-dependencies as the parent pom.

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-dependencies</artifactId>
        <version>2.1.0.RELEASE</version>
        <relativePath>../../spring-boot-dependencies</relativePath>
    </parent>

The spring-boot-dependencies manage curated list of all the dependencies while the starter parents handle the plugin configurations and other defaults. This is how our parent pom looks like:

<properties>
   <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
   <java.version>1.8</java.version>
   <resource.delimiter>@</resource.delimiter>
   <maven.compiler.source>${java.version}</maven.compiler.source>
   <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   <maven.compiler.target>${java.version}</maven.compiler.target>
</properties>

The properties section defines some of the application defaults. Spring Boot will use these default values in case none is defined in your project’s application.properties file.

<pluginManagement>
    <plugins>
	<plugin>
	  <groupId>org.jetbrains.kotlin</groupId>
	   <artifactId>kotlin-maven-plugin</artifactId>
	   <version>${kotlin.version}</version>
	      <executions>
		<execution>
		  <id>compile</id>
		  <phase>compile</phase>
		     <goals>
			<goal>compile</goal>
		      </goals>
		  </execution>
                  <!-- other execution goals -->
		  <configuration>
		      <jvmTarget>${java.version}</jvmTarget>
		       <javaParameters>true</javaParameters>
		</configuration>
	</plugin>
	<!-- othrer plugins -->
   </plugins>
<pluginManagement>

 

1.2 Spring Boot Dependencies

The Spring Boot dependencies manage the list of the dependencies as part of the dependencies management system.This is how it look like:

<properties>
	<activemq.version>5.15.7</activemq.version>
	<antlr2.version>2.7.7</antlr2.version>
	<appengine-sdk.version>1.9.67</appengine-sdk.version>
	<artemis.version>2.6.3</artemis.version>
	<aspectj.version>1.9.2</aspectj.version>
	<assertj.version>3.11.1</assertj.version>
	<atomikos.version>4.0.6</atomikos.version>
	<bitronix.version>2.1.4</bitronix.version>
	<build-helper-maven-plugin.version>3.0.0</build-helper-maven-plugin.version>
	<byte-buddy.version>1.9.3</byte-buddy.version>
	<caffeine.version>2.6.2</caffeine.version>
	<cassandra-driver.version>3.6.0</cassandra-driver.version>
	<!-- List of other dependencies -->
</properties>
<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot</artifactId>
			<version>2.1.0.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-actuator</artifactId>
			<version>2.1.0.RELEASE</version>
		</dependency>
		<!-- other list -->
	</dependencies>
</dependencyManagement>

 

2. Spring Boot Without Parent

Spring Boot starter parent takes care of a number of things for us and it is highly recommended to inherit this in your pom.xml file. There are a few use cases where you may not like to inherit the spring-boot-starter-parent POM. To handle such use case, Spring Boot provides the flexibility to still use the dependency management without inheriting it.

<dependencyManagement>
    <dependencies>
        <dependency>
            <!-- Import dependency management from Spring Boot -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>2.1.1.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

We are using a scope=import for this. Once this configuration is in place, we can start adding Spring dependencies as per our requirement. This is how we can add dependencies:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <!-- if we need to override the version -->
            <version>2.1.1.RELEASE</version>
        </dependency>
    </dependencies>
</dependencyManagement>

The version tag is optional. This is useful if we want to use a different version for a certain dependency than the one managed by Boot.

 

Summary

In this article, we talk about the Spring Boot starter parent. We covered the dependency and plugin management using starter parent in your project. We also talk about how to use spring boot without parent pom.xml file.