71. Spring Boot Maven Plugin

The Spring Boot Maven Plugin provides Spring Boot support in Maven, letting you package executable jar or war archives and run an application “in-place”. To use it, you must use Maven 3.2 (or later).

[Note]Note

See the Spring Boot Maven Plugin Site for complete plugin documentation.

71.1 Including the Plugin

To use the Spring Boot Maven Plugin, include the appropriate XML in the plugins section of your pom.xml, as shown in the following example:

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<!-- ... -->
	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<version>2.1.11.BUILD-SNAPSHOT</version>
				<executions>
					<execution>
						<goals>
							<goal>repackage</goal>
						</goals>
					</execution>
				</executions>
			</plugin>
		</plugins>
	</build>
</project>

The preceding configuration repackages a jar or war that is built during the package phase of the Maven lifecycle. The following example shows both the repackaged jar as well as the original jar in the target directory:

$ mvn package
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original

If you do not include the <execution/> configuration, as shown in the prior example, you can run the plugin on its own (but only if the package goal is used as well), as shown in the following example:

$ mvn package spring-boot:repackage
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original

If you use a milestone or snapshot release, you also need to add the appropriate pluginRepository elements, as shown in the following listing:

<pluginRepositories>
	<pluginRepository>
		<id>spring-snapshots</id>
		<url>https://repo.spring.io/snapshot</url>
	</pluginRepository>
	<pluginRepository>
		<id>spring-milestones</id>
		<url>https://repo.spring.io/milestone</url>
	</pluginRepository>
</pluginRepositories>

71.2 Packaging Executable Jar and War Files

Once spring-boot-maven-plugin has been included in your pom.xml, it automatically tries to rewrite archives to make them executable by using the spring-boot:repackage goal. You should configure your project to build a jar or war (as appropriate) by using the usual packaging element, as shown in the following example:

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<!-- ... -->
	<packaging>jar</packaging>
	<!-- ... -->
</project>

Your existing archive is enhanced by Spring Boot during the package phase. The main class that you want to launch can be specified either by using a configuration option, as shown below, or by adding a Main-Class attribute to the manifest. If you do not specify a main class, the plugin searches for a class with a public static void main(String[] args) method.

<plugin>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-maven-plugin</artifactId>
	<configuration>
		<mainClass>com.example.app.Main</mainClass>
	</configuration>
</plugin>

To build and run a project artifact, you can type the following:

$ mvn package
$ java -jar target/mymodule-0.0.1-SNAPSHOT.jar

To build a war file that is both executable and deployable into an external container, you need to mark the embedded container dependencies as “provided”, as shown in the following example:

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<!-- ... -->
	<packaging>war</packaging>
	<!-- ... -->
	<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>
		<!-- ... -->
	</dependencies>
</project>
[Tip]Tip

See the “Section 92.1, “Create a Deployable War File”” section for more details on how to create a deployable war file.

Advanced configuration options and examples are available in the plugin info page.