责任链（Chain of Responsibility）模式 ：责任链模式是对象的行为模式。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受者直接的耦合关系。将这些对象连成一条链，沿着这条链传递该请求，直到有一个对象处理它为止。责任链模式强调的是每一个对象及其对下家的引用来组成一条链，利用这种方式将发送者和接收者解耦，类图如下：
package chainOfResp;
public abstract class Handler {
protected Handler successor;
public abstract void handlerRequest(String condition);
public Handler getSuccessor() {
return successor;
}
public void setSuccessor(Handler successor) {
this.successor = successor;
}
}
package chainOfResp;
public class ConcreteHandler1 extends Handler {
@Override
public void handlerRequest(String condition) {
// 如果是自己的责任，就自己处理，负责传给下家处理
if(condition.equals("ConcreteHandler1")){
System.out.println( "ConcreteHandler1 handled ");
return ;
}else{
System.out.println( "ConcreteHandler1 passed ");
getSuccessor().handlerRequest(condition);
}
}
}
package chainOfResp;
public class ConcreteHandler2 extends Handler {
@Override
public void handlerRequest(String condition) {
// 如果是自己的责任，就自己处理，负责传给下家处理
if(condition.equals("ConcreteHandler2")){
System.out.println( "ConcreteHandler2 handled ");
return ;
}else{
System.out.println( "ConcreteHandler2 passed ");
getSuccessor().handlerRequest(condition);
}
}
}
package chainOfResp;
public class ConcreteHandlerN extends Handler {
/**
* 这里假设n是链的最后一个节点必须处理掉
* 在实际情况下，可能出现环，或者是树形，
* 这里并不一定是最后一个节点。
*
*/
@Override
public void handlerRequest(String condition) {
System.out.println( "ConcreteHandlerN handled");
}
}
package chainOfResp;
public class Client {
public static void main(String[] args) {
Handler handler1 = new ConcreteHandler1();
Handler handler2 = new ConcreteHandler2();
Handler handlern = new ConcreteHandlerN();
//链起来
handler1.setSuccessor(handler2);
handler2.setSuccessor(handlern);
//假设这个请求是ConcreteHandler2的责任
handler1.handlerRequest("ConcreteHandler2");
}
}
package chainOfResp.example;
public abstract class Handler {
protected Handler handler;
public abstract boolean approve(double day);
public Handler getHandler() {
return handler;
}
public void setHandler(Handler handler) {
this.handler = handler;
}
}
package chainOfResp.example;
public class GroupLeader extends Handler {
@Override
public boolean approve(double day) {
if(day<0.5){
System.out.println("小组长审批通过");
return true;
}else {
System.out.println("小组长传给了他的上司");
return getHandler().approve(day);
}
}
}
package chainOfResp.example;
public class ProjectManager extends Handler {
@Override
public boolean approve(double day) {
if(day<2){
System.out.println("项目经理审批通过");
return true;
}else {
System.out.println("项目经理传给了他的上司");
return getHandler().approve(day);
}
}
}
package chainOfResp.example;
public class DepartmentManager extends Handler {
@Override
public boolean approve(double day) {
if(day<5){
System.out.println("部门经理审批通过");
return true;
}else {
System.out.println("部门经理传给了他的上司");
return getHandler().approve(day);
}
}
}
package chainOfResp.example;
public class CEO extends Handler {
@Override
public boolean approve(double day) {
System.out.println("部门经理审批通过");
return true;
}
}
package chainOfResp.example;
public class Client {
public static void main(String[] args) {
//创建节点
GroupLeader gl = new GroupLeader();
ProjectManager pm = new ProjectManager();
DepartmentManager dm = new DepartmentManager();
CEO ceo = new CEO();
//建立责任链
gl.setHandler(pm);
pm.setHandler(dm);
dm.setHandler(ceo);
//向小组长发出申请，请求审批4天的假期
gl.approve(4D);
}
}
运行结果：
原文：http://www.cnblogs.com/liujun5020/p/5421309.html