责任链模式

责任链模式：使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。将这些对象连成一条链，并顺着这条链传递该请求，直到有一个对象处理它为止。以下是例子：

//接口Request拥有getType与execute方法 

public class RequestStudent implements Request{

public String getType() {

return "StudentRequest";

}

public void execute() {

System.out.println("[RequestStudent] :\t Students request has been accepted!");

}

}

//handlerRequest是接口Handler 的方法

public class HandlerStudent implements Handler {

private Handler nextSuccessor;

public HandlerStudent(Handler nextSuccessor){

this.nextSuccessor = nextSuccessor; }

public void handlerRequest(Request request) {

// 处理StudentRequest

if(request.getType().equalsIgnoreCase("StudentRequest")){

System.out.println("HandlerStudent begin to response StudentRequest;");

request.execute(); }

else{

//把请求传递给其他受理者

if(this.nextSuccessor!=null){

nextSuccessor.handlerRequest(request); }

else{

System.out.println("request[" + request.getType() + "] has not handler to deal!"); } } } }

//测试类 

public class Test { public static void main(String[] args) {  

Handler handler = new HandlerStudent(new HandlerTeacher(new HandlerSchoolmaster(null)));

Request studentReq = new RequestStudent();

Request teacherReq = new RequestTeacher();

Request schoolmasterReq = new RequestSchoolmaster();

Request presidentReq = new RequestPresident();

//传入student request

handler.handlerRequest(studentReq);

System.out.println("=========");

//传入teacher request

handler.handlerRequest(teacherReq);

System.out.println("=========");

//传入schoolmaster request

handler.handlerRequest(schoolmasterReq);

System.out.println("=========");

//传入president request

handler.handlerRequest(presidentReq);

System.out.println("========="); } }