To use querydsl-collections without generated query types you need to use the Querydsl alias feature. Here are some examples.

To get started, add the following static imports :

import static com.mysema.query.alias.Alias.*;

And now create an alias instance for the Cat class. Alias instances can only be created for classes with an empty constructor. Make sure your class has one.

The alias instance of type Cat and its getter invocations are transformed into Querydsl paths by wrapping them into dollar method invocations. The call c.getKittens() for example is internally transformed into the property path c.kittens inside the dollar method.

Cat c = alias(Cat.class, "cat");
for (String name : from($(c),cats)
  .where($(c.getKittens()).size().gt(0))
  .list($(c.getName()))){
    System.out.println(name);
}

The following example is a variation of the previous, where the access to the list size happens inside the dollar-method invocation.

Cat c = alias(Cat.class, "cat");
for (String name : from($(c),cats)
  .where($(c.getKittens().size()).gt(0))
  .list($(c.getName()))){
    System.out.println(name);
}

All non-primitive and non-String typed properties of aliases are aliases themselves. So you may cascade method calls until you hit a primitive or non-Bean type (e.g. java.lang.String) in the dollar-method scope.

e.g.

$(c.getMate().getName())

is transformed into c.mate.name internally, but

$(c.getMate().getName().toLowerCase())

is not transformed properly, since the toLowerCase() invocation is not tracked.

Note also that you may only invoke getters, size(), contains(Object) and get(int) on alias types. All other invocations throw exceptions.

The example above can be expressed like this with generated query types

QCat cat = new QCat("cat");
for (String name : from(cat,cats)
  .where(cat.kittens.size().gt(0))
  .list(cat.name)){
    System.out.println(name);
}

When you use generated query types, you instantiate query types instead of alias instances and use the property paths directly without any dollar-method wrapping.

If you are not using JPA or JDO you can generate Querydsl query types for your domain types by annotating them with the com.mysema.query.annotations.QueryEntity annotation and adding the following plugin configuration into your Maven configuration (pom.xml) :

<project>
  <build>
  <plugins>
    ...
    <plugin>
      <groupId>com.mysema.maven</groupId>
      <artifactId>maven-apt-plugin</artifactId>
      <version>1.0.2</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>

Place the jar files from the full-deps bundle on your classpath and use the following tasks for Querydsl code generation :

    <!-- APT based code generation -->
    <javac srcdir="${src}" classpathref="cp">
      <compilerarg value="-proc:only"/>      
      <compilerarg value="-processor"/>
      <compilerarg value="com.mysema.query.apt.QuerydslAnnotationProcessor"/>
      <compilerarg value="-s"/>
      <compilerarg value="${generated}"/>
    </javac>
    
    <!-- compilation -->
    <javac classpathref="cp" destdir="${build}">      
      <src path="${src}"/>
      <src path="${generated}"/>
    </javac>    

Replace src with your main source folder, generated with your folder for generated sources and build with your target folder.