Add the following dependency to your Maven project and make sure that the Maven 2 repo of Mysema Source (http://source.mysema.com/maven2/releases) is accessible from your POM :

<http://xslthl.sf.net:tag><dependency></http://xslthl.sf.net:tag>
  <http://xslthl.sf.net:tag><groupId></http://xslthl.sf.net:tag>com.mysema.querydsl<http://xslthl.sf.net:tag></groupId></http://xslthl.sf.net:tag>
  <http://xslthl.sf.net:tag><artifactId></http://xslthl.sf.net:tag>querydsl-hql<http://xslthl.sf.net:tag></artifactId></http://xslthl.sf.net:tag>
  <http://xslthl.sf.net:tag><version></http://xslthl.sf.net:tag>0.4.0<http://xslthl.sf.net:tag></version></http://xslthl.sf.net:tag>
<http://xslthl.sf.net:tag></dependency></http://xslthl.sf.net:tag>

And now, configure the Maven APT plugin :

<http://xslthl.sf.net:tag><project></http://xslthl.sf.net:tag>
  <http://xslthl.sf.net:tag><build></http://xslthl.sf.net:tag>
  <http://xslthl.sf.net:tag><plugins></http://xslthl.sf.net:tag>
    ...
    <http://xslthl.sf.net:tag><plugin></http://xslthl.sf.net:tag>
      <http://xslthl.sf.net:tag><groupId></http://xslthl.sf.net:tag>com.mysema.maven<http://xslthl.sf.net:tag></groupId></http://xslthl.sf.net:tag>
      <http://xslthl.sf.net:tag><artifactId></http://xslthl.sf.net:tag>maven-apt-plugin<http://xslthl.sf.net:tag></artifactId></http://xslthl.sf.net:tag>
      <http://xslthl.sf.net:tag><version></http://xslthl.sf.net:tag>0.3.0<http://xslthl.sf.net:tag></version></http://xslthl.sf.net:tag>
      <http://xslthl.sf.net:tag><executions></http://xslthl.sf.net:tag>
        <http://xslthl.sf.net:tag><execution></http://xslthl.sf.net:tag>
          <http://xslthl.sf.net:tag><goals></http://xslthl.sf.net:tag>
            <http://xslthl.sf.net:tag><goal></http://xslthl.sf.net:tag>process<http://xslthl.sf.net:tag></goal></http://xslthl.sf.net:tag>
          <http://xslthl.sf.net:tag></goals></http://xslthl.sf.net:tag>
          <http://xslthl.sf.net:tag><configuration></http://xslthl.sf.net:tag>
            <http://xslthl.sf.net:tag><outputDirectory></http://xslthl.sf.net:tag>target/generated-sources/java<http://xslthl.sf.net:tag></outputDirectory></http://xslthl.sf.net:tag>
            <http://xslthl.sf.net:tag><processor></http://xslthl.sf.net:tag>com.mysema.query.hql.apt.JPAAnnotationProcessor<http://xslthl.sf.net:tag></processor></http://xslthl.sf.net:tag>
          <http://xslthl.sf.net:tag></configuration></http://xslthl.sf.net:tag>
        <http://xslthl.sf.net:tag></execution></http://xslthl.sf.net:tag>
      <http://xslthl.sf.net:tag></executions></http://xslthl.sf.net:tag>
    <http://xslthl.sf.net:tag></plugin></http://xslthl.sf.net:tag>
    ...
  <http://xslthl.sf.net:tag></plugins></http://xslthl.sf.net:tag>
  <http://xslthl.sf.net:tag></build></http://xslthl.sf.net:tag>
<http://xslthl.sf.net:tag></project></http://xslthl.sf.net:tag>

The JPAAnnotationProcessor finds domain types annotated with the javax.persistence.Entity annotation and generates query types for them.

Run mvn eclipse:eclipse or clean install and you will get your Query types generated into target/generated-sources/java. Now you are able to construct JPAQL/HQL query instances and instances of the query domain model.

To create queries with Querydsl you need to instantiate variables and Query implementations. We will start with the variables.

Let's assume that your project has the following domain type :

@Entity
public class Customer {
  private String firstName;
  private String lastName;

  public String getFirstName(){
    return firstName;
  }

  public String getLastName(){
    return lastName;
  }

  public void setFirstName(String fn){
    firstName = fn;
  }

  public void setLastName(String ln)[
    lastName = ln;
  }
}

Querydsl will generate a query type with the simple name QCustomer into the same package as Customer. QCustomer can be used as a statically typed variable in Querydsl queries as a representative for the Customer type.

QCustomer has a default instance variable which can be accessed as a static field :

QCustomer customer = QCustomer.customer;

Alternatively you can define your own Customer variables like this :

QCustomer customer = new QCustomer("myCustomer");

For the HQL-module HQLQueryImpl is the main Query implementation. It is instantiated like this :

HQLQuery query = new HQLQueryImpl (session); // where session is a Hibernate session

To retrieve the customer with the first name Bob you would construct a query like this :

QCustomer customer = QCustomer.customer;
HQLQuery query = new HQLQueryImpl (session);
Customer bob = query.from(customer)
  .where(customer.firstName.eq("Bob"))
  .uniqueResult(customer);

The from call defines the query source, the where part defines the filter and uniqueResult defines the projection and tells Querydsl to return a single element. Easy, right?