dtoGen^™ Book

dtoGen^™ aims to provide you with a reliable solution for generating data transfer objects by fetching/ensembling only the needed information from your domain model classes ^[1]. Usually in a N-tier solution the domain model classes reside on the server side. The domain model classes are used for fetching/saving your info from/into a persistence storage (as a relational db, filesystem, etc). According to J2EE guiding rules, a good practice is to use data transfer objects ^[2] for transfering the domain model info through the layers, this requiring hand-writting of another graph of objects.

dtoGen^™ tries to take this responsibility from the developer and let him concentrate on the real business.

I have imagined dtoGen^™ to be used in the following scenarios: ^[3]

You can find out more about these scenarios by looking at the DTO definitions upon which dtoGen^™ is tested. (test directory).

I use in this document the following definitions

dtoGen^™ uses 3 different javadoc tags on 2 java code elements:

We can imagine that any entity can provide a set of identity fields^[4] because any domain model object is uniquely identifiable by some means.

Required parameters

The dto.gen.class tag and dto.gen.property use required parameters. If these are missing than the tag is dismissed and some error/warning message is printed.

toString generation

For the generation of toString method inside a DTO I do the following checks: if there are any java bean properties having the class tag param use-in-tostring set to true than the generate-tostring must also be set to true. In case the generate-tostring is set to true and no java bean properties has the param use-in-tostring set to true than an empty toString method is generated.

equals generation

The validations done for generating equals ^[5] method inside the DTO are the same as for toString generation.

One of the most interesting things done automatically by dtoGen^™ is the deep conversion of type. I will explain here the algorithms used for the type conversions.

 /**
  * @dto.gen.class class="FooDTO"
  */
 public class Foo {
   private String  name;
   private Bar bar;
   private FooBar country;
   
   // getters and setters
   /**
    * @dto.gen.property dtos="FooDTO"
    */
   public String getName() {
     [...]
   }
   
   /**
    * @dto.gen.property dtos="FooDTO"
    */
   public Bar getBar() {
     [...]
   }
   
   /**
    * @dto.gen.property dtos="FooDTO"
    */
    public FooBar getFooBar() {
      [...]
    }
 }
          

public class FooDTO implements java.io.Serializable {
  private String name;
  private BarDTO address;
  private FooBar country;
  [...]
}
          

/**
 * @dto.gen.class class="FooDTO"
 */
public class Foo {
  private String name;
  
  /**
   * @dto.gen.property dtos="FooDTO" name="personName"
   */
  public String getName() {
    [...]
  }
}
          

public class FooDTO implements java.io.Serializable {
  private String personName;
  
  public String getPersonName() {
    [...]
  }
}
          

/**
 * @dto.gen.class class="FooDTO"
 */
public class Foo {
  private Long longValue;
  
  /**
   * @dto.gen.property dtos="FooDTO"
   *                   type="Integer"
   */
  public Long getLongValue() {
    [...]
  }
}
          

public class FooDTO {
  private Integer longValue;
  
  [...]
}
          

[still to come]

[still to come]

This chapter is a simple list of known issues/todos to be solved asap. Each will give also the solution and the schedule.

This chapter will be written when I will feel it is needed.

I must thank the following for their contribution: