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1.定义
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，并沿着这条链传递该请求，直到有一个对象处理它为止。
2.结构图
Handler：定义职责的接口，通常在这里定义处理请求的方法，可以在这里实现后继链。
ConcreteHandler：实现职责的类，在这个类中，实现对在它职责范围内请求的处理，如果处理，就继续转发请求给后继者。
Client：职责链的客户端，向链上的具体处理对象提交请求，让职责链负责处理。
3.本质
职责链模式的本质：分离职责，动态组合。
4.Code Demo
Handler.java
package org.fool.dp.cor;
public abstract class Handler {
protected Handler successor;
public void setSuccessor(Handler successor) {
this.successor = successor;
}
public abstract void handleRequest();
}ConcreteHandler1.java
package org.fool.dp.cor;
public class ConcreteHandler1 extends Handler {
@Override
public void handleRequest() {
boolean someCondition = false;
if (someCondition) {
System.out.println("ConcreteHandler1 invoked...");
} else {
if (successor != null) {
successor.handleRequest();
}
}
}
}ConcreteHandler2.java
package org.fool.dp.cor;
public class ConcreteHandler2 extends Handler {
@Override
public void handleRequest() {
boolean someCondition = false;
if (someCondition) {
System.out.println("ConcreteHandler2 invoked...");
} else {
if (successor != null) {
successor.handleRequest();
}
}
}
}ConcreteHandler3.java
package org.fool.dp.cor;
public class ConcreteHandler3 extends Handler {
@Override
public void handleRequest() {
boolean someCondition = true;
if (someCondition) {
System.out.println("ConcreteHandler3 invoked...");
} else {
if (successor != null) {
successor.handleRequest();
}
}
}
}Client.java
package org.fool.dp.cor;
public class Client {
public static void main(String[] args) {
Handler handler1 = new ConcreteHandler1();
Handler handler2 = new ConcreteHandler2();
Handler handler3 = new ConcreteHandler3();
handler1.setSuccessor(handler2);
handler2.setSuccessor(handler3);
handler1.handleRequest();
}
}