复合实体模式用于EJB持久性机制. Composite实体是EJB实体bean,它表示对象图.更新复合实体时,内部相关对象bean会自动更新为EJB实体bean管理.以下是Composite Entity Bean的参与者.
复合实体 - 它是主要实体bean .它可以是粗粒度的,也可以包含粗粒度对象以用于持久性目的.
粗粒度对象 - 这对象包含依赖对象.它有自己的生命周期,也管理依赖对象的生命周期.
依赖对象 - 依赖对象是一个依赖的对象粗粒度对象的持久化生命周期.
策略 - 策略表示如何实现复合实体.
我们将创建充当CompositeEntity的 CompositeEntity 对象. CoarseGrainedObject 将是一个包含依赖对象的类. CompositeEntityPatternDemo ,我们的演示类将使用 Client 类来演示复合实体模式的使用.
创建从属对象.
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 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()}; } }
创建粗粒度对象.
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()}; } }
创建复合实体.
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(); } }
创建客户端类以使用复合实体.
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); } }
使用客户端演示复合实体设计模式用法.
CompositeEntityPatternDemo.java
public class CompositeEntityPatternDemo { public static void main(String[] args) { Client client = new Client(); client.setData("Test", "Data"); client.printData(); client.setData("Second Test", "Data1"); client.printData(); } }
验证输出.
Data: Test Data: Data Data: Second Test Data: Data1