Maven compile with multiple src directories

java

maven-plugin

build-helper-maven-plugin

java-configuration

byAlex Kataev·Jan 21, 2025

To have Maven compile Java code from multiple directories, you'll need to modify the pom.xml file in your project, using the build-helper-maven-plugin to add the extra source paths. Insert these paths within the <sources> tag. Here's a basic example:

<build>
  <plugins>
    <plugin>
      <groupId>org.codehaus.mojo</groupId>
      <artifactId>build-helper-maven-plugin</artifactId>
      <version>3.2.0</version>
      <executions>
        <execution>
          <phase>generate-sources</phase> <!-- It's about to get source-y in here -->
          <goals>
            <goal>add-source</goal> <!-- More is merrier, right? -->
          </goals>
          <configuration>
            <sources>
              <source>src/other/java</source> <!-- Where the other half lives -->
            </sources>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

With the above snippet noting your directory path, Maven will compile both src/main/java (the default) and src/other/java (your additional path).

Step-by-step Guide: Juggling multiple `src` directories

Having additional src directories in a Maven managed project asks you to tread carefully since Maven is generally accustomed to a standard directory layout. It might take extra effort to make Maven feel at home in this newly tweaked environment.

Identifying and Adding Source Directories

Firstly, identify the director(ies) holding your additional source codes. Add them to your pom.xml using build-helper-maven-plugin. Remember, Maven is source-agnostic, as long as it's within src, it's all Java to it.

Managing Dependencies

Each source directory will carry its set of dependencies. Maven should be aware of all these external 'guests' you're inviting. Include these dependencies in your project to ensure a smooth build.

Resolving Conflicts

Multiple src directories might lead to duplicated classes or resource files. These conflicts need to be resolved before Maven can go about its compiling business, or it might throw a tantrum.

Exploring Plugin Configuration

To convince Maven into accounting for surplus src directories, it's vital that the build-helper-maven-plugin and its execution is bound to the generate-sources phase. By doing this, we ensure that no source is left unread when it's compilation time.

Ensuring Plugin Compatibility

Remember, your Maven copes better under familiar environments. Always cross-verify the build-helper-maven-plugin version against your Maven's version to avoid any compatibility interruptions during your coffee breaks.

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