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Contributing to Spring Boot

Spring Boot is released under the Apache 2.0 license. If you would like to contribute something, or simply want to hack on the code this document should help you get started.

Sign the Contributor License Agreement

Before we accept a non-trivial patch or pull request we will need you to sign the contributor’s agreement. Signing the contributor’s agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do. Active contributors might be asked to join the core team, and given the ability to merge pull requests.

Code Conventions and Housekeeping

None of these is essential for a pull request, but they will all help. They can also be added after the original pull request but before a merge.

Use the Spring Framework code format conventions. If you use Eclipse and you follow the `Importing into eclipse'' instructions below you should get project specific formatting automatically. You can also import formatter settings using the `eclipse-code-formatter.xml file from the eclipse folder. If using IntelliJ, you can use the Eclipse Code Formatter Plugin to import the same file.
Make sure all new .java files to have a simple Javadoc class comment with at least an @author tag identifying you, and preferably at least a paragraph on what the class is for.
Add the ASF license header comment to all new .java files (copy from existing files in the project)
Add yourself as an @author to the .java files that you modify substantially (more than cosmetic changes).
Add some Javadocs and, if you change the namespace, some XSD doc elements.
A few unit tests would help a lot as well — someone has to do it.
If no-one else is using your branch, please rebase it against the current master (or other target branch in the main project).

Working with the code

If you don’t have an IDE preference we would recommend that you use Spring Tools Suite or Eclipse when working with the code. We use the m2eclipe eclipse plugin for maven support. Other IDEs and tools should also work without issue.

Building from source

To build the source you will need to install Apache Maven v3.0.6 or above and JDK 1.7.

Default build

The project can be built from the root directory using the standard maven command:

$ mvn clean install

Note	You may need to increase the amount of memory available to Maven by setting a `MAVEN_OPTS` environment variable with the value `-Xmx512m -XX:MaxPermSize=128m`

If you are rebuilding often, you might also want to skip the tests until you are ready to submit a pull request:

$ mvn clean install -DskipTests

Full Build

Multi-module Maven builds cannot directly include maven plugins that are part of the reactor unless they have previously been built. Unfortunately this restriction causes some compilations for Spring Boot as we include a maven plugin and use it within the samples. The standard build works around this restriction by launching the samples via the maven-invoker-plugin so that they are not part of the reactor. This works fine most of the time, however, sometimes it useful to run a build that includes all modules (for example when using maven-versions-plugin. We use the full build on our CI servers and during the release process.

Running a full build is a two phase process.

1) Prepare the build

Preparing the build will compile and install the spring-boot-maven-plugin so that it can be referenced during the full build. It also generates a settings.xml file that enables a snapshot, milestone or release profiles based on the version being build. To prepare the build, from the root directory use:

$ mvn -P snapshot,prepare install -DskipTests

Note	You may notice that preparing the build also changes the `spring-boot-starter-parent` POM. This is required for our release process to work correctly.

2) Run the full build

Once the build has been prepared, you can run a full build using the following commands:

$ mvn -s ./settings.xml -f spring-boot-full-build -P full clean install

Note

As for the standard build, you may need to increase the amount of memory available to Maven by setting a MAVEN_OPTS environment variable with the value -Xmx512m -XX:MaxPermSize=128m. We generate more artifacts when running the full build (such as Javadoc jars), so you may find the process a little slower than the standard build.

Importing into eclipse with m2eclipse

We recommend the m2eclipe eclipse plugin when working with eclipse. If you don’t already have m2eclipse installed it is available from the "eclipse marketplace".

Spring Boot includes project specific source formatting settings, in order to have these work with m2eclipse, we provide an additional eclipse plugin that you can install:

Download org.eclipse.m2e.maveneclipse.site.zip from https://github.com/philwebb/m2eclipse-maveneclipse/releases.
Select Install new software from the help menu
Click Add… to add a new repository
Click the Archive… button
Select the org.eclipse.m2e.maveneclipse.site.zip that you previously downloaded
Install "Maven Integration for the maven-eclipse-plugin"

Note	This plugin is optional. Projects can be imported without the plugin, your code changes just won’t be automatically formatted.

With the requisite eclipse plugins installed you can select import existing maven projects from the file menu to import the code. You will need to import the root spring-boot pom and the spring-boot-samples pom separately.

Importing into eclipse without m2eclipse

If you prefer not to use m2eclipse you can generate eclipse project metadata using the following command:

$ mvn eclipse:eclipse

The generated eclipse projects can be imported by selecting import existing projects from the file menu.

Importing into other IDEs

Maven is well supported by most Java IDEs. Refer to you vendor documentation.

Integration tests

The sample application are used as integration tests during the build (when you mvn install). Due to the fact that they make use of the spring-boot-maven-plugin they cannot be called directly, and so instead are launched via the maven-invoker-plugin. If you encounter build failures running the integration tests, check the build.log file in the appropriate sample directory.