3.2. Alternative code generation

3.2. Alternative code generation
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The Java 6 APT annotation processing functionality is used in Querydsl for code generation in the JPA, JDO and Mongodb modules. For cases where annotated Java souces are not available, such as the usage of a different JVM language such as Scala or Groovy or annotation addition via bytecode manipulation the GenericExporter class can be used to scan the classpath for annotated classes and generate query types for them.

GenericExporter can be used directly or via the querydsl-maven-plugin.

3.2.1. Direct usage

To make GenericExporter available add a dependency to the querydsl-codegen module to your project, or to be more precise com.mysema.querydsl:querydsl-codegen:${querydsl.version}.

Below is an example for JPA

    		
GenericExporter exporter = new GenericExporter();
exporter.setKeywords(Keywords.JPA);
exporter.setEntityAnnotation(Entity.class);
exporter.setEmbeddableAnnotation(Embeddable.class);
exporter.setEmbeddedAnnotation(Embedded.class);        
exporter.setSupertypeAnnotation(MappedSuperclass.class);
exporter.setSkipAnnotation(Transient.class);
exporter.setTargetFolder(new File("target/generated-sources/java"));
exporter.export(DomainClass.class.getPackage());

This will export all the JPA annotated classes in the package of the DomainClass class and subpackages to the target/generated-sources/java directory.

3.2.2. Usage via Maven

The goals generic-export, jpa-export and jdo-export of the querydsl-maven-plugin can be used for GenericExporter usage via Maven.

Here is an example for JPA annotated classes

    		
<plugin>
  <groupId>com.mysema.querydsl</groupId>
  <artifactId>querydsl-maven-plugin</artifactId>
  <version>${querydsl.version}</version>  
  <executions>
    <execution>    
      <goals>
        <goal>jpa-export</goal>
      </goals>
      <configuration>
        <targetFolder>target/generated-sources/java</targetFolder>
        <packages>
          <package>com.example.domain</package>
        </packages>
      </configuration>      
    </execution>
  </executions>
</plugin>

This will export the JPA annotated classes of the com.example.domain package and subpackages to the target/generated-sources/java directory.

If you need Scala output of the classes, use a variant of the following configuration

    					
<plugin>
  <groupId>com.mysema.querydsl</groupId>
  <artifactId>querydsl-maven-plugin</artifactId>
  <version>${querydsl.version}</version>  
  <dependencies>
    <dependency>
      <groupId>com.mysema.querydsl</groupId>
      <artifactId>querydsl-scala</artifactId>
      <version>${project.version}</version>
    </dependency>
    <dependency>
      <groupId>org.scala-lang</groupId>
      <artifactId>scala-library</artifactId>
      <version>${scala.version}</version>
    </dependency>
  </dependencies>
  <executions>
    <execution>
      <goals>
        <goal>jpa-export</goal>
      </goals>
      <configuration>
        <targetFolder>target/generated-sources/scala</targetFolder>
        <scala>true</scala>
        <packages>
          <package>com.example.domain</package>
        </packages>       
      </configuration>
    </execution>
  </executions>
</plugin>