How to Compile Multiple Java Source Directories in a Single Maven Project

How can I compile multiple Java source directories within a single Maven project?

<build>
    <sourceDirectory>src/main/java</sourceDirectory>
    <sourceDirectory>src/other/java</sourceDirectory>
</build>

Maven, a popular build automation tool for Java projects, allows for the configuration of multiple source directories to compile Java files. This can be particularly useful when your project has different directories for various modules or components.

<project>
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>multiple-sources</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <sourceDirectory>src/main/java</sourceDirectory>
        <sourceDirectory>src/other/java</sourceDirectory>
    </build>
</project>

Causes

• Single source directory by default: Maven assumes a standard directory structure, which typically has one main source directory.
• Need for custom setup: For projects where code is organized across multiple directories, additional configuration is needed.

Solutions

• Use '<build>' element in 'pom.xml': Define multiple source directories within the build section of the pom.xml file.
• Combine source directories using the 'sourceSets' plugin for more complex configurations.

Mistake: Forgetting to configure the build section in pom.xml

Solution: Always ensure you've added the source directories inside the <build> section to avoid compile errors.

Mistake: Incorrectly specifying the path to source directories

Solution: Double-check the paths provided in 'pom.xml' to ensure they are accurate.