一、责任链模式的优点
责任链模式非常显著的优点是将请求和处理分开。请求者可以不用知道是谁处理的，处理者可以不用知道请求的全貌，两者解耦，提供系统的灵活性。
二、责任链模式的缺点
责任链有两个非常显著的缺点：一是性能问题，每个请求都是从链头遍历到链尾，特别是在链比较长的时候，性能是一个非常大的问题，。二是调试很不方便，特别是链条比较长，环节比较多的时候，由于采用了类似递归的方式，调试的时候逻辑可能比较复杂。
三、责任链模式的注意事项
链中节点数量需要控制，避免出现超长链的情况，一般的作做法是在Handler中设置一个最大节点数量，在setNext方法中判断是否已经是超过其阀值，超过则不允许该链建立，避免无意识地破坏系统性能。
四、最佳实践
在通用源码中Handler是抽象类，融合了模板方法模式，每个实现类只要实现两个方法，echo方法处理请求和getHandlerLevel获得处理级别，想想单一职责和迪米特法则，通过融合模板方式，各个实现类只要关注自己业务逻辑就成了，至于说什么事要自己处理，就让父类去决定，也就是说父类实现了请求传递的功能，子类实现请求的处理，符合单一职责原则，各个实现类只完成一个动作或逻辑，也就是只有一个原因引起类的改变。
责任链屏蔽了请求的处理过程，你发起一个请求到底是谁处理的，这个你不需要关系，只要你把请求抛给责任链的第一个处理者，最终都会返回一个结果，作为请求者可以不用知道到底是谁来处理的，这是责任链的核心。
五、代码示例
未使用责任链模式之前
package com.slp.responsibility;
public interface IHandler {
public void HandlerMessage(IWomen women);
}
package com.slp.responsibility;
public interface IWomen {
/**
* 获得个人情况
* @return
*/
public int getType();
/**
* 获得个人请示，要做什么？出去逛街？约会？还是看电影？
* @return
*/
public String getRequest();
}
package com.slp.responsibility;
public class Father implements IHandler {
/**
* 未出嫁的女儿请示父亲
*/
@Override
public void HandlerMessage(IWomen women) {
System.out.println("女儿的请求是："+women.getRequest());
System.out.println("父亲的答复是：同意");
}
}
package com.slp.responsibility;
public class Husband implements IHandler {
@Override
public void HandlerMessage(IWomen women) {
System.out.println("妻子的请求是："+women.getRequest());
System.out.println("丈夫的答复是：同意");
}
}
package com.slp.responsibility;
public class Son implements IHandler {
@Override
public void HandlerMessage(IWomen women) {
System.out.println("母亲的请求是："+women.getRequest());
System.out.println("儿子的答复是：同意");
}
}
package com.slp.responsibility;
public class Women implements IWomen {
/**
* 通过int类型的参数来描述个人状况
*/
private int type = 0;
/**
* 获取函数传过来的请求
*/
private String request = "";
@Override
public int getType() {
return this.type;
}
@Override
public String getRequest() {
return this.request;
}
public Women(int type, String request) {
super();
this.type = type;
this.request = request;
}
}
package com.slp.responsibility;
import java.util.ArrayList;
import java.util.Random;
public class Client {
public static void main(String[] args) {
Random random = new Random();
ArrayList<IWomen> arrayList = new ArrayList();
for(int i=0;i<5;i++){
arrayList.add(new Women(random.nextInt(4),"我要出去逛街"));
}
IHandler father = new Father();
IHandler husband = new Husband();
IHandler son = new Son();
for (IWomen women : arrayList) {
if(women.getType()==1){
System.out.println("女儿向父亲请示");
father.HandlerMessage(women);
}else if(women.getType()==2){
System.out.println("妻子向丈夫请示");
husband.HandlerMessage(women);
}else if(women.getType()==3){
System.out.println("母亲向儿子请示");
son.HandlerMessage(women);
}else{
System.out.println("不做处理");
}
}
}
}
使用责任链模式之后
package com.slp.responsibility.renew;
public interface IWomen {
/**
* 获得个人情况
* @return
*/
public int getType();
/**
* 获得个人请示，要做什么？出去逛街？约会？还是看电影？
* @return
*/
public String getRequest();
}
package com.slp.responsibility.renew;
public abstract class Handler {
public final static int FATHER_LEVEL_REQUEST = 1;
public final static int HUSBAND_LEVEL_REQUEST = 2;
public final static int SON_LEVEL_REQUEST = 1;
//能处理的级别
private int level = 0;
//责任传递，下一个责任人是谁
private Handler nextHandler;
//每个类都有说明一下自己能处理哪些请求
public Handler(int level) {
this.level = level;
}
//一个女性要求逛街，要按这个请求处理
public final void HandleMessage(IWomen women){
if(women.getType() == this.level){
this.response(women);
}else{
//有后续环节，才把请求往后递送
if(this.nextHandler!=null){
this.nextHandler.response(women);
}else{
System.out.println("---已经没有后续处理人了，按不同意处理---");
}
}
}
protected abstract void response(IWomen women);
public void setNext(Handler handler){
this.nextHandler = handler;
}
}
package com.slp.responsibility.renew;
public class Father extends Handler{
public Father() {
super(Handler.FATHER_LEVEL_REQUEST);
}
@Override
protected void response(IWomen women) {
System.out.println("-----女儿向父亲请示----");
System.out.println(women.getRequest());
System.out.println("父亲的答复是：同意\n");
}
}
package com.slp.responsibility.renew;
public class Husband extends Handler {
public Husband() {
super(Handler.HUSBAND_LEVEL_REQUEST);
}
@Override
protected void response(IWomen women) {
System.out.println("----妻子向丈夫请示----");
System.out.println(women.getRequest());
System.out.println("丈夫的答复是：同意\n");
}
}
package com.slp.responsibility.renew;
public class Son extends Handler {
public Son() {
super(Handler.SON_LEVEL_REQUEST);
}
@Override
protected void response(IWomen women) {
System.out.println("------母亲向儿子请示------");
System.out.println(women.getRequest());
System.out.println("儿子的答复是：同意\n");
}
}
package com.slp.responsibility.renew;
public class Women implements IWomen {
private int type = 0;
private String request ="";
public Women(int type, String request) {
super();
this.type = type;
switch (this.type){
case 1:
this.request="女儿的请求是："+request;
break;
case 2:
this.request="妻子的请求是："+request;
break;
case 3:
this.request="母亲的请求是："+request;
break;
}
}
@Override
public int getType() {
return this.type;
}
@Override
public String getRequest() {
// TODO Auto-generated method stub
return this.request;
}
}
package com.slp.responsibility.renew;
import java.util.ArrayList;
import java.util.Random;
public class Client {
public static void main(String[] args) {
Random random = new Random();
ArrayList<IWomen> arrayList = new ArrayList();
for(int i=0;i<5;i++){
arrayList.add(new Women(random.nextInt(4),"我要出去逛街"));
}
Handler father = new Father();
Handler husband = new Husband();
Handler son = new Son();
father.setNext(husband);
husband.setNext(son);
for(IWomen women :arrayList){
father.HandleMessage(women);
}
}
}