package de.peguform.projectmanager.project.hibernate;

import java.io.Serializable;

public class Project {
   
   public class ProjectPK implements Serializable{
      
      ProjectPK(){
         
      }
      private String name;
      private int createdate;
      
      public int getCreatedate() {
         return createdate;
      }
      public void setCreatedate(int createdate) {
         this.createdate = createdate;
      }
      public String getName() {
         return name;
      }
      public void setName(String name) {
         this.name = name;
      }
      
   }
   
   private String name;
   private int createdate;
   private String description;
   private String creator;
   private ProjectPK projectPK;
   
   public Project(){
      projectPK = new ProjectPK();
   }
   public int getCreatedate() {
      return createdate;
   }
   public void setCreatedate(int createdate) {
      this.createdate = createdate;
      projectPK.setCreatedate(createdate);
   }
   public String getCreator() {
      return creator;
   }
   public void setCreator(String creator) {
      this.creator = creator;
   }
   public String getDescription() {
      return description;
   }
   public void setDescription(String description) {
      this.description = description;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
      projectPK.setName(name);
   }
   public ProjectPK getProjectPK() {
      return projectPK;
   }
   public void setProjectPK(ProjectPK projectPK) {
      this.projectPK = projectPK;
   }

}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
  <class name="de.peguform.projectmanager.project.hibernate.Project" table="Project">
   <composite-id name="projectPK" class="de.peguform.projectmanager.project.hibernate.Project$ProjectPK">
   
   <key-property name="name" column="name"/>
   <key-property name="createdate" column="createdate"/>
   </composite-id>
 
  <property name="description">
    <column name="description"/>
  </property>
  <property name="creator">
    <column name="creator"/>
  </property>
   </class>
</hibernate-mapping>

package de.peguform.projectmanager.user.hibernate;

import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class User {
   
   
   private String username;
   private String firstname;
   private String lastname;
   private String role;
   private String email;
   private Set projects = new HashSet() ;
   
   public String getEmail() {
      return email;
   }
   public void setEmail(String email) {
      this.email = email;
   }
   public String getFirstname() {
      return firstname;
   }
   public void setFirstname(String firstname) {
      this.firstname = firstname;
   }
   public String getLastname() {
      return lastname;
   }
   public void setLastname(String lastname) {
      this.lastname = lastname;
   }
   public String getRole() {
      return role;
   }
   public void setRole(String role) {
      this.role = role;
   }
   public String getUsername() {
      return username;
   }
   public void setUsername(String username) {
      this.username = username;
   }
   public Set getProjects() {
      return projects;
   }
   public void setProjects(Set projects) {
      this.projects = projects;
   }
   
}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
   <class name="de.peguform.projectmanager.user.hibernate.User"
      table="User">
      <id name="username" column="username" />


      <property name="lastname">
         <column name="lastname" />
      </property>
      <property name="firstname">
         <column name="firstname" />
      </property>
      <property name="role">
         <column name="role" />
      </property>
      <property name="email">
         <column name="email" />
      </property>
      
      <set name="projects">
            <key column="creator"/>
            <one-to-many class="de.peguform.projectmanager.project.hibernate.Project" />
            
        </set>
   </class>
</hibernate-mapping>

Hibernate: select this_.username as username0_0_, this_.lastname as lastname0_0_, this_.firstname as firstname0_0_, this_.role as role0_0_, this_.email as email0_0_ from User this_
userBenjaZ
Hibernate: select projects0_.creator as creator1_, projects0_.name as name1_, projects0_.createdate as createdate1_, projects0_.name as name1_0_, projects0_.createdate as createdate1_0_, projects0_.description as descript3_1_0_, projects0_.creator as creator1_0_ from Project projects0_ where projects0_.creator=?
Exception in thread "main" org.hibernate.InstantiationException: No default constructor for entity: de.peguform.projectmanager.project.hibernate.Project$ProjectPK
   at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:84)
   at org.hibernate.tuple.component.AbstractComponentTuplizer.instantiate(AbstractComponentTuplizer.java:89)
   at org.hibernate.type.ComponentType.instantiate(ComponentType.java:482)
   at org.hibernate.type.ComponentType.instantiate(ComponentType.java:488)
   at org.hibernate.type.ComponentType.resolve(ComponentType.java:580)
   at org.hibernate.type.ComponentType.nullSafeGet(ComponentType.java:275)
   at org.hibernate.loader.Loader.getKeyFromResultSet(Loader.java:1088)
   at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:553)
   at org.hibernate.loader.Loader.doQuery(Loader.java:689)
   at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
   at org.hibernate.loader.Loader.loadCollection(Loader.java:1985)
   at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:36)
   at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:565)
   at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60)
   at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1716)
   at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:344)
   at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:86)
   at org.hibernate.collection.PersistentSet.iterator(PersistentSet.java:163)
   at Testclass.main(Testclass.java:28)

ProjectPK(Project project)
{
....
}