= 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.



== Code of Conduct
This project adheres to the Contributor Covenant link:CODE_OF_CONDUCT.adoc[code of
conduct]. By participating, you are expected to uphold this code. Please report
unacceptable behavior to spring-code-of-conduct@pivotal.io.



== Using GitHub Issues
We use GitHub issues to track bugs and enhancements. If you have a general usage question
please ask on https://stackoverflow.com[Stack Overflow]. The Spring Boot team and the
broader community monitor the https://stackoverflow.com/tags/spring-boot[`spring-boot`]
tag.

If you are reporting a bug, please help to speed up problem diagnosis by providing as much
information as possible. Ideally, that would include a small
https://github.com/spring-projects/spring-boot-issues[sample project] that reproduces the
problem.



== Reporting Security Vulnerabilities
If you think you have found a security vulnerability in Spring Boot please *DO NOT*
disclose it publicly until we've had a chance to fix it. Please don't report security
vulnerabilities using GitHub issues, instead head over to https://pivotal.io/security and
learn how to disclose them responsibly.



== Sign the Contributor License Agreement
Before we accept a non-trivial patch or pull request we will need you to
https://cla.pivotal.io/sign/spring[sign the Contributor License 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.

* We use the https://github.com/spring-io/spring-javaformat/[Spring JavaFormat] project
  to apply code formatting conventions. If you use Eclipse and you follow the '`Importing
  into eclipse`' instructions below you should get project specific formatting
  automatically. You can also install the https://github.com/spring-io/spring-javaformat/#intellij-idea[Spring JavaFormat IntelliJ Plugin]
  or format the code from the Maven build by running
  `./mvnw io.spring.javaformat:spring-javaformat-maven-plugin:apply`.
* The build includes checkstyle rules for many of our code conventions. Run
  `./mvnw validate` if you want to check you changes are compliant.
* 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.
* 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).
* When writing a commit message please follow https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html[these conventions],
  if you are fixing an existing issue please add `Fixes gh-XXXX` at the end of the commit
  message (where `XXXX` is the issue number).



== Working with the Code
If you don't have an IDE preference we would recommend that you use
https://spring.io/tools/sts[Spring Tools Suite] or
https://eclipse.org[Eclipse] when working with the code. We use the
https://eclipse.org/m2e/[M2Eclipse] eclipse plugin for maven support. Other IDEs and tools
should also work without issue.



=== Building from Source
Spring Boot source can be built from the command line using
https://maven.apache.org/run-maven/index.html[Apache Maven] on JDK 1.8 or above.
We include '`Maven Wrapper`' scripts (`./mvnw` or `mvnw.bat`) that you can run rather
than needing to install Maven locally.



==== Default Build
The project can be built from the root directory using the standard Maven command:

[indent=0]
----
	$ ./mvnw 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`

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

[indent=0]
----
	$ ./mvnw clean install -DskipTests -Pfast
----



==== 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's 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
built. To prepare the build, from the root directory use:

[indent=0]
----
	$ ./mvnw -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:

[indent=0]
----
	$ ./mvnw -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`. 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
You can import the Spring Boot code into any Eclipse 2019-03-based distribution. The
easiest way to setup a new environment is to use the Eclipse Installer with the provided
`spring-boot-project.setup` file (in the `/eclipse` folder).


==== Using the Eclipse Installer
Spring Boot includes a `.setup` files which can be used with the Eclipse Installer to
provision a new environment. To use the installer:

* Download and run the latest
  https://www.eclipse.org/downloads/packages/installer[Eclipse Installer].
* Switch to "Advanced Mode" using the drop down menu on the right.
* Select "`Eclipse IDE for Java Developers`" under "`Eclipse.org`" as the product to
  install, `2019-03` as the product version, and click "`next`".
* For the "`Project`" click on "`+`" to add a new setup file. Select "`Github Projects`"
  and browse for `<checkout>/eclipse/spring-boot-project.setup` from your locally cloned
  copy of the source code. Click "`OK`" to add the setup file to the list.
* Double-click on "`Spring Boot`" from the project list to add it to the list that will
  be provisioned then click "`Next`".
* Click show all variables and make sure that "`Checkout Location`" points to the locally
  cloned source code that you selected earlier. You might also want to pick a different
  install location here.
* Click "`Finish`" to install the software.

Once complete you should find that a local workspace has been provisioned complete with
all required Eclipse plugins. Projects will be grouped into working-sets to make the code
easier to navigate.

If you want to work on the `spring-boot-gradle-plugin` you should remove the imported Maven
project and reimport it as a Gradle project.

TIP: If you see import errors with `com.sun` packages make sure you have setup a valid
`JavaSE-1.8` environment. From preferences select "`Java`", "`Installed JREs`",
"`Execution Environments`" and make sure "`JavaSE-1.8`" points to a Java 1.8
install (we use AdoptOpenJDK on our CI).



==== Manual Installation with M2Eclipse
If you prefer to install Eclipse yourself you should use the
https://eclipse.org/m2e/[M2Eclipse] eclipse plugin. 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:



===== Install the Spring Formatter plugin
* Select "`Help`" -> "`Install New Software`".
* Add `https://dl.bintray.com/spring/javaformat-eclipse/` as a site.
* Install "Spring Java Format"

NOTE: The plugin is optional. Projects can be imported without the plugins, 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 Other IDEs
Maven is well supported by most Java IDEs. Refer to your vendor documentation.



== Integration Tests
The sample applications are used as integration tests during the build (when you
`./mvnw 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.
