（行为型模式六）责任链模式

package com.eyugame.modle;

/**
 * 责任链模式
 *
 * @author JYC506
 *
 */
/* 事件接收者 */
public abstract class EventReceiver {

	private EventReceiver nextEventReceiver;

	public void setNextHandler(EventReceiver nextEventReceiver) {
		this.nextEventReceiver = nextEventReceiver;
	}

	public Response handleRequest(Request request) {
		if (this.isOk(request)) {
			return this.getResponse();
		} else {
			if (this.nextEventReceiver != null) {
				return this.nextEventReceiver.handleRequest(request);
			} else {
				System.out.println("没有合适的事件接收者");
				return null;
			}
		}
	}

	public abstract Response getResponse();

	protected abstract boolean isOk(Request request);

	public static void main(String[] args) {
		/* 创建一个请求 */
		Request request = new Request(Command.EVENT2);
		/* 非责任链模式下的代码 */
		if (request.getCommand() == Command.EVENT1) {
			new EventReceiver1().handleRequest(request);
		} else if (request.getCommand() == Command.EVENT2) {
			new EventReceiver2().handleRequest(request);
		} else if (request.getCommand() == Command.EVENT3) {
			new EventReceiver3().handleRequest(request);
		} else if (request.getCommand() == Command.EVENT4) {
			new EventReceiver4().handleRequest(request);
		}
		/* 责任链模式下的代码 */
		/* 是不是责任链模式比较清晰点，低耦合,不过比较耗内存，因为都是提前并全部new出对象 */
		EventReceiver receiver1 = new EventReceiver1();
		EventReceiver receiver2 = new EventReceiver2();
		EventReceiver receiver3 = new EventReceiver3();
		EventReceiver receiver4 = new EventReceiver4();
		receiver1.setNextHandler(receiver2);
		receiver2.setNextHandler(receiver3);
		receiver3.setNextHandler(receiver4);
		receiver1.handleRequest(request);
	}
}
/*返回结果类*/
class Response {

}

/* 请求 */
class Request {

	Command command;

	public Request(Command command) {
		super();
		this.command = command;
	}

	public Command getCommand() {
		return command;
	}

	public void setCommand(Command command) {
		this.command = command;
	}

}

/* 请求命令 */
enum Command {
	EVENT1, EVENT2, EVENT3, EVENT4
}

class EventReceiver1 extends EventReceiver {

	@Override
	public Response getResponse() {
		System.out.println("事件处理者1处理并返回结果");
		return null;
	}

	@Override
	protected boolean isOk(Request request) {
		return request.getCommand() == Command.EVENT1;
	}

}

class EventReceiver2 extends EventReceiver {

	@Override
	public Response getResponse() {
		System.out.println("事件处理者2处理并返回结果");
		return null;
	}

	@Override
	protected boolean isOk(Request request) {
		return request.getCommand() == Command.EVENT2;
	}

}

class EventReceiver3 extends EventReceiver {

	@Override
	public Response getResponse() {
		System.out.println("事件处理者3处理并返回结果");
		return null;
	}

	@Override
	protected boolean isOk(Request request) {
		return request.getCommand() == Command.EVENT3;
	}

}

class EventReceiver4 extends EventReceiver {

	@Override
	public Response getResponse() {
		System.out.println("事件处理者4处理并返回结果");
		return null;
	}

	@Override
	protected boolean isOk(Request request) {
		return request.getCommand() == Command.EVENT3;
	}

}