Spring Boot includes build plugins for Maven and Gradle. This section answers common questions about these plugins.
Both the Maven plugin and the Gradle plugin allow generating build information containing
the coordinates, name, and version of the project. The plugins can also be configured
to add additional properties through configuration. When such a file is present,
Spring Boot auto-configures a BuildProperties
bean.
To generate build information with Maven, add an execution for the build-info
goal, as
shown in the following example:
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>2.0.0.RELEASE</version> <executions> <execution> <goals> <goal>build-info</goal> </goals> </execution> </executions> </plugin> </plugins> </build>
![]() | Tip |
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See the Spring Boot Maven Plugin documentation for more details. |
The following example does the same with Gradle:
springBoot { buildInfo() }
![]() | Tip |
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See the Spring Boot Gradle Plugin documentation for more details. |
Both Maven and Gradle allow generating a git.properties
file containing information
about the state of your git
source code repository when the project was built.
For Maven users, the spring-boot-starter-parent
POM includes a pre-configured plugin to
generate a git.properties
file. To use it, add the following declaration to your POM:
<build> <plugins> <plugin> <groupId>pl.project13.maven</groupId> <artifactId>git-commit-id-plugin</artifactId> </plugin> </plugins> </build>
Gradle users can achieve the same result by using the
gradle-git-properties
plugin, as shown in the following example:
plugins { id "com.gorylenko.gradle-git-properties" version "1.4.17" }
![]() | Tip |
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The commit time in |
If you use a Maven build that inherits directly or indirectly from
spring-boot-dependencies
(for instance, spring-boot-starter-parent
) but you want to
override a specific third-party dependency, you can add appropriate <properties>
elements. Browse the
spring-boot-dependencies
POM for a complete list of properties. For example, to pick a different slf4j
version,
you would add the following property:
<properties> <slf4j.version>1.7.5<slf4j.version> </properties>
![]() | Note |
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Doing so only works if your Maven project inherits (directly or indirectly) from
|
![]() | Warning |
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Each Spring Boot release is designed and tested against this specific set of third-party dependencies. Overriding versions may cause compatibility issues. |
The spring-boot-maven-plugin
can be used to create an executable “fat” JAR. If you
use the spring-boot-starter-parent
POM, you can declare the plugin and your jars are
repackaged as follows:
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
If you do not use the parent POM, you can still use the plugin. However, you must
additionally add an <executions>
section, as follows:
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>2.0.0.RELEASE</version> <executions> <execution> <goals> <goal>repackage</goal> </goals> </execution> </executions> </plugin> </plugins> </build>
See the plugin documentation for full usage details.
Like a war file, a Spring Boot application is not intended to be used as a dependency. If your application contains classes that you want to share with other projects, the recommended approach is to move that code into a separate module. The separate module can then be depended upon by your application and other projects.
If you cannot rearrange your code as recommended above, Spring Boot’s Maven and Gradle
plugins must be configured to produce a separate artifact that is suitable for use as a
dependency. The executable archive cannot be used as a dependency as the
executable jar
format packages application classes in BOOT-INF/classes
. This means
that they cannot be found when the executable jar is used as a dependency.
To produce the two artifacts, one that can be used as a dependency and one that is executable, a classifier must be specified. This classifier is applied to the name of the executable archive, leaving the default archive for use as a dependency.
To configure a classifier of exec
in Maven, you can use the following configuration:
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <classifier>exec</classifier> </configuration> </plugin> </plugins> </build>
Most nested libraries in an executable jar do not need to be unpacked in order to run.
However, certain libraries can have problems. For example, JRuby includes its own nested
jar support, which assumes that the jruby-complete.jar
is always directly available as a
file in its own right.
To deal with any problematic libraries, you can flag that specific nested jars should be automatically unpacked to the “temp folder” when the executable jar first runs.
For example, to indicate that JRuby should be flagged for unpacking by using the Maven Plugin, you would add the following configuration:
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <requiresUnpack> <dependency> <groupId>org.jruby</groupId> <artifactId>jruby-complete</artifactId> </dependency> </requiresUnpack> </configuration> </plugin> </plugins> </build>
Often, if you have an executable and a non-executable jar as two separate build products,
the executable version has additional configuration files that are not needed in a library
jar. For example, the application.yml
configuration file might by excluded from the
non-executable JAR.
In Maven, the executable jar must be the main artifact and you can add a classified jar for the library, as follows:
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> <plugin> <artifactId>maven-jar-plugin</artifactId> <executions> <execution> <id>lib</id> <phase>package</phase> <goals> <goal>jar</goal> </goals> <configuration> <classifier>lib</classifier> <excludes> <exclude>application.yml</exclude> </excludes> </configuration> </execution> </executions> </plugin> </plugins> </build>
To attach a remote debugger to a Spring Boot application that was started with Maven, you
can use the jvmArguments
property of the maven plugin.
See this example for more details.
To build with Ant, you need to grab dependencies, compile, and then create a jar or war
archive. To make it executable, you can either use the spring-boot-antlib
module or you can follow these instructions:
BOOT-INF/classes
directory. If you are building a war, package the application’s
classes in a nested WEB-INF/classes
directory as usual.BOOT-INF/lib
directory for a jar or
WEB-INF/lib
for a war. Remember not to compress the entries in the archive.provided
(embedded container) dependencies in a nested BOOT-INF/lib
directory for a jar or WEB-INF/lib-provided
for a war. Remember not to compress the
entries in the archive.spring-boot-loader
classes at the root of the archive (so that the Main-Class
is available).JarLauncher
for a jar file) as a Main-Class
attribute in the manifest and specify the other properties it needs as manifest entries — principally, by setting a Start-Class
property.The following example shows how to build an executable archive with Ant:
<target name="build" depends="compile"> <jar destfile="target/${ant.project.name}-${spring-boot.version}.jar" compress="false"> <mappedresources> <fileset dir="target/classes" /> <globmapper from="*" to="BOOT-INF/classes/*"/> </mappedresources> <mappedresources> <fileset dir="src/main/resources" erroronmissingdir="false"/> <globmapper from="*" to="BOOT-INF/classes/*"/> </mappedresources> <mappedresources> <fileset dir="${lib.dir}/runtime" /> <globmapper from="*" to="BOOT-INF/lib/*"/> </mappedresources> <zipfileset src="${lib.dir}/loader/spring-boot-loader-jar-${spring-boot.version}.jar" /> <manifest> <attribute name="Main-Class" value="org.springframework.boot.loader.JarLauncher" /> <attribute name="Start-Class" value="${start-class}" /> </manifest> </jar> </target>
The Ant Sample has a
build.xml
file with a manual
task that should work if you run it with the following
command:
$ ant -lib <folder containing ivy-2.2.jar> clean manual
Then you can run the application with the following command:
$ java -jar target/*.jar