Improvement to code generated projects

In my previous post Executing a maven 2 plugin task more than once I exhibited an example where it's possible to run a plugin task a few times to generate several JAXB java beans from a XSD schema. The problem with this approach is that it is still not very intuitive since you'll find yourself filling your project dir with extra directories for generated src files ($basedir/packageA and $basedir/packageB in our case). This creates confusion since you'll soon lose track of these files and attempt to check them in to the respository if you are not careful.

That being said, I'll show you a better alternative to organize your projects. To get started, let's lay out the proposed structure (this time we will have 1 project for each XSD and then another project for the java project that uses them):

+-my_java_project
| `-src/main/java
| `-src/main/resources
|
+-my_xsd_project_a
| `-src/main/resources
|
`-my_xsd_project_b
  `-src/main/resources

Now, let's examine the pom.xml used for XSD projects:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mycompany</groupId>
  <artifactId>my_xsd_project_a</artifactId>
  <packaging>jar</packaging>
  <name>My Company - Project A</name>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.jvnet.jaxb2.maven2</groupId>
        <artifactId>maven-jaxb2-plugin</artifactId>
        <executions>
          <!-- Configuration for packageA -->
          <execution>
          <goals>
            <goal>generate</goal>
          </goals>
          </execution>
        </executions>

        <!-- Common JAXB configuration -->
        <configuration>
          <!-- Changes the default schema directory -->
          <schemaDirectory>../xml-schemas-project/</schemaDirectory>
          <extension>true</extension>
          <generatePackage>com.mycompany.packageA</generatePackage>
          <generateDirectory>generated-src-packageA</generateDirectory>
          <schemaIncludes>
          <include>xml-schemas/packageA/packageA.xsd</include>
          </schemaIncludes>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

Note that the configuration section has been extracted out of the <execution/> tag since we don't have any other <execution/> which needs particular configuration, thus we can move the configuration to the global configuration part of the plugin.

Next, if we run "mvn clean install" we will get a package with the generated classes in it. So, in order to use the generated classes we only need to include the my_xsd_project_a project as a maven2 dependency to my_java_project and that's it. Here's an example:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mycompany</groupId>
  <artifactId>my_java_project</artifactId>
  <packaging>jar</packaging>
  <name>My Company - My Java Project</name>
  ...
  <dependencies>
    <!-- Dependency to my_xsd_project_a (generated by JAXB) -->
    <dependency>
      <groupId>com.mycompany</groupId>
      <artifactId>my_xsd_project_a</artifactId>
    </dependency>

    <!-- Dependency to my_xsd_project_b (generated by JAXB) -->
    <dependency>
      <groupId>com.mycompany</groupId>
      <artifactId>my_xsd_project_b</artifactId>
    </dependency>
  </dependencies>
</project>