责任链（Chain Of Responsibility）模式
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责任链（Chain Of Responsibility）
Intent
通过这种方式让多个对象都有机会处理请求,从而防止请求的发送者和接收者之间存在的耦合关系.将这些对象连接成一个链条,并依次沿着这条链条发送该请求,直到其中一个对象处理它为止.
Class Diagram
- Handler：定义处理请求的接口，并且实现后继链（successor）
Implementation
public abstract class Handler {
protected Handler successor;
public Handler(Handler successor) {
this.successor = successor;
}
protected abstract void handleRequest(Request request);
}
代码解读 public class ConcreteHandler1 extends Handler {
public ConcreteHandler1(Handler successor) {
super(successor);
}
@Override
protected void handleRequest(Request request) {
if (request.getType() == RequestType.TYPE1) {
System.out.println(request.getName() + " is handle by ConcreteHandler1");
return;
}
if (successor != null) {
successor.handleRequest(request);
}
}
}
代码解读 public class ConcreteHandler2 extends Handler {
public ConcreteHandler2(Handler successor) {
super(successor);
}
@Override
protected void handleRequest(Request request) {
if (request.getType() == RequestType.TYPE2) {
System.out.println(request.getName() + " is handle by ConcreteHandler2");
return;
}
if (successor != null) {
successor.handleRequest(request);
}
}
}
代码解读 public class Request {
private RequestType type;
private String name;
public Request(RequestType type, String name) {
this.type = type;
this.name = name;
}
public RequestType getType() {
return type;
}
public String getName() {
return name;
}
}
代码解读 public enum RequestType {
TYPE1, TYPE2
}
代码解读 public class Client {
public static void main(String[] args) {
Handler handler1 = new ConcreteHandler1(null);
Handler handler2 = new ConcreteHandler2(handler1);
Request request1 = new Request(RequestType.TYPE1, "request1");
handler2.handleRequest(request1);
Request request2 = new Request(RequestType.TYPE2, "request2");
handler2.handleRequest(request2);
}
}
代码解读 request1 is handle by ConcreteHandler1
request2 is handle by ConcreteHandler2
代码解读JDK
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