Design Patterns - Composite Entity Pattern

Composite Entity pattern is used in EJB persistence mechanism. A Composite entity is an EJB entity bean which represents a graph of objects. When a composite entity is updated, internally dependent objects beans get updated automatically as being managed by EJB entity bean. Following are the participants in Composite Entity Bean.

Composite Entity - It is primary entity bean. It can be coarse grained or can contain a coarse grained object to be used for persistence purpose.

Coarse-Grained Object - This object contains dependent objects. It has its own pfe cycle and also manages pfe cycle of dependent objects.

Dependent Object - Dependent object is an object which depends on coarse grained object for its persistence pfecycle.

Strategies - Strategies represents how to implement a Composite Entity.

Implementation

We are going to create CompositeEntity object acting as CompositeEntity. CoarseGrainedObject will be a class which contains dependent objects. CompositeEntityPatternDemo, our demo class will use Cpent class to demonstrate use of Composite Entity pattern.

Step 1

Create Dependent Objects.

DependentObject1.java

pubpc class DependentObject1 {
	
   private String data;

   pubpc void setData(String data){
      this.data = data; 
   } 

   pubpc String getData(){
      return data;
   }
}

DependentObject2.java

pubpc class DependentObject2 {
	
   private String data;

   pubpc void setData(String data){
      this.data = data; 
   } 

   pubpc String getData(){
      return data;
   }
}

Step 2

Create Coarse Grained Object.

CoarseGrainedObject.java

pubpc class CoarseGrainedObject {
   DependentObject1 do1 = new DependentObject1();
   DependentObject2 do2 = new DependentObject2();

   pubpc void setData(String data1, String data2){
      do1.setData(data1);
      do2.setData(data2);
   }

   pubpc String[] getData(){
      return new String[] {do1.getData(),do2.getData()};
   }
}

Step 3

Create Composite Entity.

CompositeEntity.java

pubpc class CompositeEntity {
   private CoarseGrainedObject cgo = new CoarseGrainedObject();

   pubpc void setData(String data1, String data2){
      cgo.setData(data1, data2);
   }

   pubpc String[] getData(){
      return cgo.getData();
   }
}

Step 4

Create Cpent class to use Composite Entity.

Cpent.java

pubpc class Cpent {
   private CompositeEntity compositeEntity = new CompositeEntity();

   pubpc void printData(){
   
      for (int i = 0; i < compositeEntity.getData().length; i++) {
         System.out.println("Data: " + compositeEntity.getData()[i]);
      }
   }

   pubpc void setData(String data1, String data2){
      compositeEntity.setData(data1, data2);
   }
}

Step 5

Use the Cpent to demonstrate Composite Entity design pattern usage.

CompositeEntityPatternDemo.java

pubpc class CompositeEntityPatternDemo {
   pubpc static void main(String[] args) {
   
       Cpent cpent = new Cpent();
       cpent.setData("Test", "Data");
       cpent.printData();
       cpent.setData("Second Test", "Data1");
       cpent.printData();
   }
}

Step 6

Verify the output.

Data: Test
Data: Data
Data: Second Test
Data: Data1