By default Querydsl initializes only direct reference properties. In cases where longer initialization paths are required, these have to be annotated in the domain types via com.mysema.query.annotations.QueryInit annotations. QueryInit is used on properties where deep initializations are needed. The following example demonstrates the usage.

@Entity      
class Event {
    @QueryInit("customer")
    Account account;
}      

@Entity
class Account{
    Customer customer;    
}

@Entity
class Customer{
    String name;
    // ...
}

This example enforces the initialization of the account.customer path, when an Event path is initialized as a root path / variable. The path initialization format supports wildcards as well, e.g. "customer.*" or just "*".

The automatic path initialization replaces the manual one, which required the entity fields to be non-final. The declarative format has the benefit to be applied to all top level instances of a Query type and to enable the usage of final entity fields.

Automatic path initialization is the preferred initialization strategy, but manual initialization can be activated via the Config annotation, which is described below.

The serialization of Querydsl can be customized via Config annotations on packages and types. They customize the serialization of the annotated package or type.

The serialization options are

Below are some examples.

Customization of Entity type serialization:

@Config(entityAccessors=true)
@Entity
public class User {
    //...
}     

Customization of package content:

@Config(listAccessors=true)
package com.mysema.query.domain.rel;

import com.mysema.query.annotations.Config;

If you want to customize the serializer configuration globally, you can do this via the following APT options

Using the Maven APT plugin this works for example like this:

<project>
  <build>
  <plugins>
    ...
    <plugin>
      <groupId>com.mysema.maven</groupId>
      <artifactId>apt-maven-plugin</artifactId>
      <version>1.0.9</version>
      <executions>
        <execution>
          <goals>
            <goal>process</goal>
          </goals>
          <configuration>
            <outputDirectory>target/generated-sources/java</outputDirectory>
            <processor>com.mysema.query.apt.jpa.JPAAnnotationProcessor</processor>
            <options>
              <querydsl.entityAccessors>true</querydsl.entityAccessors>
            </options>          
          </configuration>
        </execution>
      </executions>
    </plugin>
    ...
  </plugins>
  </build>
</project>

Custom type mappings can be used on properties to override the derived Path type. This can be useful for example in cases where comparison and String operations should be blocked on certain String paths or Date / Time support for custom types needs to be added. Support for Date / Time types of the Joda time API and JDK (java.util.Date, Calendar and subtypes) is built in, but other APIs might need to be supported using this feature.

The following example demonstrates the usage:

@Entity      
public class MyEntity{      
    @QueryType(PropertyType.SIMPLE)
    public String stringAsSimple;
        
    @QueryType(PropertyType.COMPARABLE)
    public String stringAsComparable;
        
    @QueryType(PropertyType.NONE)
    public String stringNotInQuerydsl;    
}        

The value PropertyType.NONE can be used to skip a property in the query type generation. This case is different from @Transient or @QueryTransient annotated properties, where properties are not persisted. PropertyType.NONE just omits the property from the Querydsl query type.

To declare a static method as a delegate method add the QueryDelegate annotation with the corresponding domain type as a value and provide a method signature that takes the corresponding Querydsl query type as the first argument.

Here is a simple example from a unit test:

   
@QueryEntity
public static class User{
       
    String name;
       
    User manager;
       
}

   
@QueryDelegate(User.class)
public static BooleanPath isManagedBy(QUser user, User other){
    return user.manager.eq(other);
}   

And the generated methods in the QUser query type:

   
public BooleanPath isManagedBy(QUser other) {
    return com.mysema.query.domain.DelegateTest.isManagedBy(this, other);
}
    

Delegate methods can also be used to extend built-in types. Here are some examples

       
public class QueryExtensions {

    @QueryDelegate(Date.class)
    public static BooleanExpression inPeriod(DatePath<Date> date, Pair<Date,Date> period){
        return date.goe(period.getFirst()).and(date.loe(period.getSecond()));
    }

    @QueryDelegate(Timestamp.class)
    public static BooleanExpression inDatePeriod(DateTimePath<Timestamp> timestamp, Pair<Date,Date> period){
        Timestamp first = new Timestamp(DateUtils.truncate(period.getFirst(), Calendar.DAY_OF_MONTH).getTime());
        Calendar second = Calendar.getInstance();
        second.setTime(DateUtils.truncate(period.getSecond(), Calendar.DAY_OF_MONTH));
        second.add(1, Calendar.DAY_OF_MONTH);
        return timestamp.goe(first).and(timestamp.lt(new Timestamp(second.getTimeInMillis())));
    }
    
}    

When delegate methods are declared for builtin types then subclasses with the proper delegate method usages are created:

      
public class QDate extends DatePath<java.sql.Date> {

    public QDate(BeanPath<? extends java.sql.Date> entity) {
        super(entity.getType(), entity.getMetadata());
    }

    public QDate(PathMetadata<?> metadata) {
        super(java.sql.Date.class, metadata);
    }

    public BooleanExpression inPeriod(com.mysema.commons.lang.Pair<java.sql.Date, java.sql.Date> period) {
        return QueryExtensions.inPeriod(this, period);
    }

}

public class QTimestamp extends DateTimePath<java.sql.Timestamp> {

    public QTimestamp(BeanPath<? extends java.sql.Timestamp> entity) {
        super(entity.getType(), entity.getMetadata());
    }

    public QTimestamp(PathMetadata<?> metadata) {
        super(java.sql.Timestamp.class, metadata);
    }

    public BooleanExpression inDatePeriod(com.mysema.commons.lang.Pair<java.sql.Date, java.sql.Date> period) {
        return QueryExtensions.inDatePeriod(this, period);
    }

}

It is possible to create Querydsl query types for non annotated types by creating @QueryEntities annotations. Just place a QueryEntities annotation into a package of your choice and the classes to mirrored in the value attribute.

To actually create the types use the com.mysema.query.apt.QuerydslAnnotationProcessor. In Maven you do it like this:

<project>
  <build>
  <plugins>
    ...
    <plugin>
      <groupId>com.mysema.maven</groupId>
      <artifactId>apt-maven-plugin</artifactId>
      <version>1.0.9</version>
      <executions>
        <execution>
          <goals>
            <goal>process</goal>
          </goals>
          <configuration>
            <outputDirectory>target/generated-sources/java</outputDirectory>
            <processor>com.mysema.query.apt.QuerydslAnnotationProcessor</processor>
          </configuration>
        </execution>
      </executions>
    </plugin>
    ...
  </plugins>
  </build>
</project>

For cases where annotated Java sources 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.

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.

            
<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>           

                        
<execution>
  <goals>
    <goal>compile</goal>
  </goals>
  <configuration>
    <sourceFolder>target/generated-sources/scala</targetFolder>
    <packages>
      <package>com.example.domain</package>
    </packages>       
  </configuration>
</execution>         

                        
<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>