定义 ：Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request .Chain the receiving objects and pass the request along the chain until an object handles it
使多个对象都有机会处理请求，从而避免了请求的发送者和接受者之间的耦合关系。 将这些对象连成一条链，并沿着这条链传递该请求，知道有对象处理它为止
例子
package ChainOfResponiability;
public interface Ixiaoming {
int getType();
String getRequest();
}
package ChainOfResponiability;
public class XiaoMing implements Ixiaoming{
private int type;
private String request;
/*
* type=1 表示爸爸在家
* type=2 表示爸爸不在妈妈在家
* @see ChainOfResponiability.Ixiaoming#getType()
*/
public XiaoMing(int type,String request){
this.type=type;
this.request=request;
//方便显示
switch(this.type){
case 1:
this.request="爸爸在家"+request;
break;
case 2:
this.request="爸爸不在妈妈在"+request;
}
}
@Override
public int getType() {
return type;
}
public String getRequest(){
return request;
}
}
package ChainOfResponiability;
public abstract class Handler {
protected final static int LEVEL1=1;
protected final static int LEVEL2=2;
private int level=0;
public Handler(int level){
this.level=level;
}
public final void handleRequest(Ixiaoming xiaoming){
if(xiaoming.getType()==this.level)
this.response(xiaoming);
else{
if(this.nextHandler!=null)
this.nextHandler.handleRequest(xiaoming);
else
System.out.println("熊孩子没人guan啦");
}
}
private Handler nextHandler;
public void setNextHandler(Handler handler){
this.nextHandler=handler;
}
protected abstract void response(Ixiaoming xiaoming);
}
package ChainOfResponiability;
public class Father extends Handler{
public Father() {
super(LEVEL2);
}
@Override
protected void response(Ixiaoming xiaoming) {
System.out.println("爸爸在家不许去");
}
}
package ChainOfResponiability;
public class Mother extends Handler{
public Mother() {
super(LEVEL1);
}
@Override
protected void response(Ixiaoming xiaoming) {
System.out.println("爸爸不再快去吧");
}
}
package ChainOfResponiability;
import java.util.ArrayList;
public class Client {
public static void main(String []args){
ArrayList<Ixiaoming> list=new ArrayList<Ixiaoming>();
list.add(new XiaoMing(1,"我要出去玩"));
list.add(new XiaoMing(2,"我要出去玩"));
list.add(new XiaoMing(3,"我要出去玩"));
Handler father=new Father();
Handler mother=new Mother();
father.setNextHandler(mother);
for(Ixiaoming i:list)
father.handleRequest(i);
}
}
看下优点：可动态添加处理程序，在无处理情况下还会提供错误处理。 Client 可以动态组装处理顺序比较方便，处理权掌握在处理链手中。
缺点: 性能问题。 链过长会导致严重的性能问题。