责任链模式

1. 抽象责任链处理者

public abstract class AbstractHandler {
    //处理级别常量定义
    public static final int HANDLE_LEVEL_FIRST = 0;
    public static final int HANDLE_LEVEL_SECOND = 1;
    //责任链下一级别
    private AbstractHandler nextHandler;
    //设置责任链下一级别
    public void setNextHandler(AbstractHandler nextHandler) {
        this.nextHandler = nextHandler;
    }
    //具体处理，本函数返回为void，可以返回具体处理结果
    public final void handle(AbstractRequest request) {
        if (request.getRequestLevel() == getHandleLevel()) {
            //当前处理级别
            this.response(request);
        } else if (nextHandler != null) {
            //下一处级别
            this.nextHandler.handle(request);
        } else {
            //没有能够处理级别
            Log.d("handler", "没有应答");
        }
    }
    //当前级别处理级别
    protected abstract int getHandleLevel();
    //当前级别响应
    protected abstract void response(AbstractRequest request);
}

2. 抽象责任链处理者实现类

public class FirstHandler extends AbstractHandler {
    @Override
    protected int getHandleLevel() {
        return AbstractHandler.HANDLE_LEVEL_FIRST;
    }
    @Override
    protected void response(AbstractRequest request) {
        //当前级别具体业务处理
        Log.d("handler", request.getRequest());
        Log.d("handler", "FirstHandler处理结果");
    }
}
public class SecondHandler extends AbstractHandler {
    @Override
    protected int getHandleLevel() {
        return AbstractHandler.HANDLE_LEVEL_SECOND;
    }
    @Override
    protected void response(AbstractRequest request) {
        //当前级别具体业务处理
        Log.d("handler", request.getRequest());
        Log.d("handler", "SecondHandler处理结果");
    }
}

3. 请求抽象类或接口

public abstract class AbstractRequest {
    //请求级别
    protected abstract int getRequestLevel();
    //获取请求内容
    protected abstract String getRequest();
}

4. 请求抽象类或接口实现类

public class ConcreteRequest extends AbstractRequest {
    @Override
    protected int getRequestLevel() {
        return AbstractHandler.HANDLE_LEVEL_FIRST;
    }
    @Override
    protected String getRequest() {
        return "请求内容";
    }
}

5. 场景使用

    //责任链角色
    AbstractHandler firstHandler = new FirstHandler();
    AbstractHandler secondHandler = new SecondHandler();
    //请求
    AbstractRequest request = new ConcreteRequest();
    //组装责任链
    firstHandler.setNextHandler(secondHandler);
    //提交请求
    firstHandler.handle(request);