10-dtos.md

DTOs

Fulib makes it easy to generate DTOs (Data Transfer Objects) from existing model classes without a lot of duplication. We recommend putting all DTOs into a package and GenDtos class that are separate from your model. Here's an example:

src/gen/java/org/example/dtos/model/GenModel:

public class GenModel implements ClassModelDecorator
{
   public class User
   {
      String id;
      String name;
      @Link("user")
      Address address;
   }

   public class Address
   {
      String id;
      String city;
      String street;
      @Link("address")
      User user;
   }

   @Override
   public void decorate(ClassModelManager m)
   {
      m.haveNestedClasses(GenModel.class);
   }
}

src/gen/java/org/example/dtos/dto/GenDtos:

public class GenDtos implements ClassModelDecorator
{
   @DTO(model = GenModel.User.class, omit = { "id" })
   class UserDto
   {}

   @DTO(model = GenModel.Address.class, pick = { "city", "street" })
   class AddressDto
   {}

   @Override
   public void decorate(ClassModelManager m)
   {
      // This omits PropertyChangeListeners etc. from the generated code
      m.getClassModel().setDefaultPropertyStyle(Type.POJO);
      m.haveNestedClasses(GenDtos.class);
   }
}

The example shows the basic usage of the @DTO annotation.

• model sets the model class we want to copy fields from.
• omit is optional and specifies which fields should not be copied to the DTO class.
• pick is optional and specifies which fields should be copied to the DTO class. If pick is provided, all other fields will be ignored.

Let's take a look at the generated code:

src/main/java/org/example/dtos/dto/UserDto.java

```java public class UserDto { public static final String PROPERTY_NAME = "name"; public static final String PROPERTY_ADDRESS = "address"; private String name; private String address;

  public String getName()
  {
     return this.name;
  }

  public UserDto setName(String value)
  {
     this.name = value;
     return this;
  }

  public String getAddress()
  {
     return this.address;
  }

  public UserDto setAddress(String value)
  {
     this.address = value;
     return this;
  }

  @Override
  public String toString()
  {
     final StringBuilder result = new StringBuilder();
     result.append(' ').append(this.getName());
     result.append(' ').append(this.getAddress());
     return result.substring(1);
  }

}

<!-- end_code_fragment: -->
</details>

<details>
<summary>
   <code>src/main/java/org/example/dtos/dto/AddressDto.java</code>
</summary>

<!-- insert_code_fragment: docs.dtos.AddressDto | fenced:java -->
```java
public class AddressDto
{
   public static final String PROPERTY_CITY = "city";
   public static final String PROPERTY_STREET = "street";
   private String city;
   private String street;

   public String getCity()
   {
      return this.city;
   }

   public AddressDto setCity(String value)
   {
      this.city = value;
      return this;
   }

   public String getStreet()
   {
      return this.street;
   }

   public AddressDto setStreet(String value)
   {
      this.street = value;
      return this;
   }

   @Override
   public String toString()
   {
      final StringBuilder result = new StringBuilder();
      result.append(' ').append(this.getCity());
      result.append(' ').append(this.getStreet());
      return result.substring(1);
   }
}

In the UserDto class, we can see that all attributes from User were copied over except for id, because it was specified in omit. The address association in User was converted to a String field, which can hold the Address ID in our DTO.

The AddressDto class contains only the city and street attributes, thanks to the pick array.

For completeness, here is the generated code for the User and Address model classes. Note how these use the default Bean property style, which generates PropertyChange support.

src/main/java/org/example/dtos/model/User.java

public class User
{
   public static final String PROPERTY_ID = "id";
   public static final String PROPERTY_NAME = "name";
   public static final String PROPERTY_ADDRESS = "address";
   private String id;
   private String name;
   private Address address;
   protected PropertyChangeSupport listeners;

   public String getId()
   {
      return this.id;
   }

   public User setId(String value)
   {
      if (Objects.equals(value, this.id))
      {
         return this;
      }

      final String oldValue = this.id;
      this.id = value;
      this.firePropertyChange(PROPERTY_ID, oldValue, value);
      return this;
   }

   public String getName()
   {
      return this.name;
   }

   public User setName(String value)
   {
      if (Objects.equals(value, this.name))
      {
         return this;
      }

      final String oldValue = this.name;
      this.name = value;
      this.firePropertyChange(PROPERTY_NAME, oldValue, value);
      return this;
   }

   public Address getAddress()
   {
      return this.address;
   }

   public User setAddress(Address value)
   {
      if (this.address == value)
      {
         return this;
      }

      final Address oldValue = this.address;
      if (this.address != null)
      {
         this.address = null;
         oldValue.setUser(null);
      }
      this.address = value;
      if (value != null)
      {
         value.setUser(this);
      }
      this.firePropertyChange(PROPERTY_ADDRESS, oldValue, value);
      return this;
   }

   public boolean firePropertyChange(String propertyName, Object oldValue, Object newValue)
   {
      if (this.listeners != null)
      {
         this.listeners.firePropertyChange(propertyName, oldValue, newValue);
         return true;
      }
      return false;
   }

   public PropertyChangeSupport listeners()
   {
      if (this.listeners == null)
      {
         this.listeners = new PropertyChangeSupport(this);
      }
      return this.listeners;
   }

   @Override
   public String toString()
   {
      final StringBuilder result = new StringBuilder();
      result.append(' ').append(this.getId());
      result.append(' ').append(this.getName());
      return result.substring(1);
   }

   public void removeYou()
   {
      this.setAddress(null);
   }
}

src/main/java/org/example/dtos/model/Address.java

public class Address
{
   public static final String PROPERTY_ID = "id";
   public static final String PROPERTY_CITY = "city";
   public static final String PROPERTY_STREET = "street";
   public static final String PROPERTY_USER = "user";
   private String id;
   private String city;
   private String street;
   private User user;
   protected PropertyChangeSupport listeners;

   public String getId()
   {
      return this.id;
   }

   public Address setId(String value)
   {
      if (Objects.equals(value, this.id))
      {
         return this;
      }

      final String oldValue = this.id;
      this.id = value;
      this.firePropertyChange(PROPERTY_ID, oldValue, value);
      return this;
   }

   public String getCity()
   {
      return this.city;
   }

   public Address setCity(String value)
   {
      if (Objects.equals(value, this.city))
      {
         return this;
      }

      final String oldValue = this.city;
      this.city = value;
      this.firePropertyChange(PROPERTY_CITY, oldValue, value);
      return this;
   }

   public String getStreet()
   {
      return this.street;
   }

   public Address setStreet(String value)
   {
      if (Objects.equals(value, this.street))
      {
         return this;
      }

      final String oldValue = this.street;
      this.street = value;
      this.firePropertyChange(PROPERTY_STREET, oldValue, value);
      return this;
   }

   public User getUser()
   {
      return this.user;
   }

   public Address setUser(User value)
   {
      if (this.user == value)
      {
         return this;
      }

      final User oldValue = this.user;
      if (this.user != null)
      {
         this.user = null;
         oldValue.setAddress(null);
      }
      this.user = value;
      if (value != null)
      {
         value.setAddress(this);
      }
      this.firePropertyChange(PROPERTY_USER, oldValue, value);
      return this;
   }

   public boolean firePropertyChange(String propertyName, Object oldValue, Object newValue)
   {
      if (this.listeners != null)
      {
         this.listeners.firePropertyChange(propertyName, oldValue, newValue);
         return true;
      }
      return false;
   }

   public PropertyChangeSupport listeners()
   {
      if (this.listeners == null)
      {
         this.listeners = new PropertyChangeSupport(this);
      }
      return this.listeners;
   }

   @Override
   public String toString()
   {
      final StringBuilder result = new StringBuilder();
      result.append(' ').append(this.getId());
      result.append(' ').append(this.getCity());
      result.append(' ').append(this.getStreet());
      return result.substring(1);
   }

   public void removeYou()
   {
      this.setUser(null);
   }
}