第二十四章 职责链模式

职责链模式（Chain of Responsibility)：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。将这个对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止。

注意：一个请求极有可能到了链末都得不到处理，或者因为没有正确配置而得不到处理。

/**
 * Created by hero on 16-4-7.
 */
public abstract class Handler {
    protected Handler successor;

    public void setSuccessor(Handler successor) {
        this.successor = successor;
    }

    public abstract void handleRequest(int request);
}
/**
 * Created by hero on 16-4-7.
 */
public class ConcreteHandler1 extends Handler {
    @Override
    public void handleRequest(int request) {
        if (request < 10) {
            System.out.println("handled by 1");
        } else if (successor != null) {
            successor.handleRequest(request);
        }
    }
}
/**
 * Created by hero on 16-4-7.
 */
public class ConcreteHandler2 extends Handler {
    @Override
    public void handleRequest(int request) {
        if (request < 20) {
            System.out.println("handled by 2");
        } else if (successor != null) {
            successor.handleRequest(request);
        } else {
            System.out.println("no handler");
        }
    }
}
public class Main {

    public static void main(String[] args) {
        ConcreteHandler1 concreteHandler1 = new ConcreteHandler1();
        ConcreteHandler2 concreteHandler2 = new ConcreteHandler2();
        concreteHandler1.setSuccessor(concreteHandler2);
        int[] requests = {10, 2, 22, 33, 7, 5};
        for (int request : requests)
            concreteHandler1.handleRequest(request);
    }
}