Dispenser mapping for a Hibernate object for DTO

Question

I am trying to use Dozer to convert a domain object into DTO objects. So, I want to convert PersistentList, PersistentBag, ... from my domain object to ArrayList, ... to my DTO objects to avoid a lazy problem.

This is an example of two objects in my domain:

public class User {
      private Collection<Role> roles;
      ...
}

public class Role {
      private Collection<User> users;
      ...
}

My DTO objects are the same, except that the class has DTO types. So, to convert the domain to DTO objects, I use the following Dozer mapping:

 <configuration>
  <custom-converters>
   <converter type=com.app.mapper.converter.BagConverter">
    <class-a>org.hibernate.collection.PersistentBag</class-a>
    <class-b>java.util.List</class-b>
   </converter>
  </custom-converters>
 </configuration>

 <mapping>
  <class-a>com.app.domain.User</class-a>
  <class-b>com.app.dto.UserDTO</class-b>
 </mapping>

 <mapping>
  <class-a>com.app.domain.Role</class-a>
  <class-b>com.app.dto.RoleDTO</class-b>
 </mapping>

BagConverter is a Dozer custom converter, which is its code:

  public class BagConverter<T> extends DozerConverter<PersistentBag, List>{

 public BagConverter() {
  super(PersistentBag.class, List.class);
 }

 public PersistentBag convertFrom(List source, PersistentBag destination) {
  PersistentBag listDest = null;

  if (source != null) {

   if (destination == null) {
    listDest = new PersistentBag();
   } else {
    listDest = destination;
   }

   listDest.addAll(source);
  }

  return listDest;
 }

 public List convertTo(PersistentBag source, List destination) {
  List listDest = null;

  if (source != null) {

   if (destination == null) {
    listDest = new ArrayList<T>();
   } else {
    listDest = destination;
   }

   if (source.wasInitialized()) {
    listDest.addAll(source);
   }
  }

  return listDest;
 }}

, User, PersistentBag . UserDTO. , , UserDTO ArrayList of Role ArrayList of RoleDTO, .

, , dozer . ? , , dto, Java?

.

Sylvain.

Answer 1

, CustomConverter, ( ), , , ..

( , - ). MapperAware, Dozer. , , .

Answer 2

Dozer DTO. , PersistentList, PersistentBag,... ArrayList,... DTO, .

, , o.h.c.PersistentBag ( ), a List. - :

<mapping>
  <class-a>com.myapp.domain.User</class-a>
  <class-b>com.myapp.dto.UserDTO</class-b>
  <field>
    <a>roles</a>
    <b>roles</b>
    <a-hint>com.myapp.domain.Role</a-hint>
    <b-hint>com.myapp.dto.RoleDTO</b-hint>
  </field>
</mapping>

, ( ).

Answer 3

:

<mapping>
    <class-a>com.myapp.domain.User</class-a>
    <class-b>com.myapp.dto.UserDTO</class-b>
    <field>
        <a>roles</a>
        <b>roles</b>
        <a-hint>com.myapp.domain.Role</a-hint>
        <b-hint>com.myapp.dto.RoleDTO</b-hint>
    </field>
</mapping>

. Dozer User RoleDTO UserDTO, Hibernate, User EAGER.

, , . .

Answer 4

, , PersistentBags. @Entity POJO java.util.List, Hibernate . , POJO . :

@Entity
public class User {
  private java.util.List<Role> roles = new java.util.Arraylist<Role>(); //Hibernate doesn't really care about this new Arraylist stuff, it will use its org.hibernate.collection.PersistentList
  ... //other fields and methods
}

, Entity POJO DTO, , Pascal, aka

<mapping>
  <class-a>com.myapp.domain.User</class-a>
  <class-b>com.myapp.dto.UserDTO</class-b>
  <field>
    <a>roles</a>
    <b>roles</b>
    <a-hint>com.myapp.domain.Role</a-hint>
    <b-hint>com.myapp.dto.RoleDTO</b-hint>
  </field>
</mapping>

, :

@Transactional
public UserDTO getUser(...) {
  User user = dao.getUser(...);
  UserDTO dto = //Place your Dozer conversion here
  return dto;
}

, Dozer , .