introduce

Composite Entity Pattern is used in EJB persistence mechanism. A composite entity is an EJB entity bean that represents the graphics of objects. When a composite entity is updated, the internally dependent object beans are automatically updated because they are managed by EJB entity beans. The following are the participants in the composite entity bean.

• Composite Entity - It is the primary entity bean. It can be coarse-grained, or it can contain a coarse-grained object for a continuous life cycle.
• Coarse-Grained Object - This object contains dependent objects. It has its own life cycle and can also manage the life cycle of dependent objects.
• Dependent Object - Dependent Object is an object whose lifecycle depends on coarse-grained objects.
• Strategies - Policies represent how to implement composite entities.

Realization

We will create a ComppositeEntity object as a composite entity. CoarseGrainedObject is a class that contains dependent objects.

Composite EntityPatternDemo, our demo class uses the Client class to demonstrate the use of composite entity patterns.

Step 1

Create dependent objects.

DependentObject1.java

public class DependentObject1 {

    private String data;

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

    public String getData(){
        return data;
    }

}

DependentObject2.java

public class DependentObject2 {

    private String data;

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

    public String getData(){
        return data;
    }

}

Step 2

Create coarse-grained objects.

CoarseGrainedObject.java

public class CoarseGrainedObject {

    DependentObject1 do1 = new DependentObject1();

    DependentObject2 do2 = new DependentObject2();

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

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

}

Step 3

Create composite entities.

CompositeEntity.java

public class CompositeEntity {

    private CoarseGrainedObject cgo = new CoarseGrainedObject();

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

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

}

Step 4

Create client classes that use composite entities.

Client.java

public class Client {

    private CompositeEntity compositeEntity = new CompositeEntity();

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

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

}

Step 5

Use Client to demonstrate the usage of composite entity design patterns.

CompositeEntityPatternDemo.java

public class CompositeEntityPatternDemo {

    public static void main(String[] args) {
        Client client = new Client();
        client.setData("Test", "Data");
        client.printData();
        System.out.println();

        client.setData("Second Test", "Data1");
        client.printData();
    }

}

Step 6

Verify the output.

Data: Test
Data: Data

Data: Second Test
Data: Data1