Maven Micro-Tip: Get sources and Javadocs

When you're using Maven in an IDE you often find the need for your IDE to resolve source code and Javadocs for your library dependencies. There's an easy way to accomplish that goal.

mvn dependency:sources
mvn dependency:resolve -Dclassifier=javadoc

The first command will attempt to download source code for each of the dependencies in your pom file.

The second command will attempt to download the Javadocs.

Maven is at the mercy of the library packagers here. So some of them won't have source code packaged and many of them won't have Javadocs.

In case you have a lot of dependencies it might also be a good idea to use inclusions/exclusions to get specific artifacts, the following command will for example only download the sources for the dependency with a specific artifactId:

mvn dependency:sources -DincludeArtifactIds=guava

Source: http://tedwise.com/2010/01/27/maven-micro-tip-get-sources-and-javadocs/

Documentation: https://maven.apache.org/plugins/maven-dependency-plugin/sources-mojo.html

If a project creates a jar of the project sources and deploys it to a maven repository, then you'll find it :)

Just FYI, sources artifacts are generally created by the maven-source-plugin. This plugin can bundle the main or test sources of a project into a jar archive and, as explained in Configuring Source Plugin:

(...) The generated jar file will be named by the value of the finalName plus "-sources" if it is the main sources. Otherwise, it would be finalName plus "-test-sources" if it is the test sources.

The additional text was given to describe an artifact ("-sources" or "-test-sources" here) is called a classifier.

To declare a dependency on an artifact that uses a classifier, simply add the <classifier> element. For example:

<dependency>
  <groupId>org.hibernate</groupId>
  <artifactId>hibernate</artifactId>
  <version>3.2.7.ga</version>
  <classifier>sources</classifier>
</dependency>

Note that you generally don't do this, most IDEs provide support to download sources (and/or JavaDoc) from the main artifact without declaring explicitly a dependency on them.

Finally, also note that some repository search engines allow searching for artifacts using the classifier (at least Nexus does with the advanced search). See this search for example.

The maven idea plugin for IntelliJ Idea allows you to specify whether or not sources and java doc should be resolved and downloaded

mvn idea:idea -DdownloadSources=true -DdownloadJavadocs=true

you can find info in this related question: Get source jar files attached to Eclipse for Maven-managed dependencies
if you use the eclipse maven plugin then use 'mvn eclipse:eclipse -DdownloadSources=true'

You can, if they are uploaded. Generally they are called "frameworkname-version-source(s)"

If you know the groupId and aritifactId,you can generate download url like this.

    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.2.3</version>
    </dependency>

http://central.maven.org/maven2/ch/qos/logback/logback-classic/

and you will get a page like this, chose the version you need,just enjoy it!

Maven repositories do provide simple way to download sources jar.

I will explain it using a demonstration for "spring-boot-actuator-autoconfigure".

1. Go to maven repository - https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-actuator-autoconfigure
2. The page lists various versions. Click-on to desired one, let's say, 2.1.6.RELEASE - https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-actuator-autoconfigure/2.1.6.RELEASE
3. The page have link "View All" next to "Files". Click it - https://repo1.maven.org/maven2/org/springframework/boot/spring-boot-actuator-autoconfigure/2.1.6.RELEASE/
4. The page lists various files including the one for sources - https://repo1.maven.org/maven2/org/springframework/boot/spring-boot-actuator-autoconfigure/2.1.6.RELEASE/spring-boot-actuator-autoconfigure-2.1.6.RELEASE-sources.jar

Otherwise, you can always "git clone" the repo from github, if its there and get the specific code.

As explained by others, you can use "mvn dependency:sources" command the get and generate sources jar for the dependency you are using.

Note: Some dependencies will not have sources.jar, as those contains no source code but a pom file. e.g. spring-boot-starter-actuator. As in this case:

Starter POMs are a set of convenient dependency descriptors that you can include in your application. You get a one-stop-shop for all the Spring and related technology that you need, without having to hunt through sample code and copy paste loads of dependency descriptors.

Reference: Intro to Spring Boot Starters

In IntelliJ IDEA you can download artifact sources automatically while importing by switching on Automatically download Sources option:

Settings → Build, Execution, Deployment → Build Tools → Maven → Importing

If you want find the source jar file for any of the artifact manually, go to maven repository location for the particular artifact and in Files click on 'view All'. You can find source jar file.

For debugging you can also use a "Java Decompiler" such as: JAD and decompile source on the fly (although the generated source is never the same as the original). Then install JAD as a plugin in Eclipse or your favorite IDE.

If you're using Eclipse, I would recommend downloading both the source and the Javadocs of third-party libraries.

Right click on project and download both as per the screenshot below.

Downloading Javadocs means that typically you can get contextual help for methods from third-party libraries, with useful description of parameters, etc. This is essential if you don't know the library well. In some cases I have found that Javadocs are available when the source isn't.