责任链模式 -- 设计模式

责任链模式（Chain of Responsibility Pattern）为请求创建了一个接收者对象的链。

思考: 责任链中的每个处理器都包含了下一个处理器的引用, 并且将需要处理的信息, 不停的传下去, 但是我怀疑会不会有栈溢出的问题

package day0320.ChainOfResponsibilityPattern;

public class Demo{

    public static void main(String[] args){
        AbstractLogger logger = new ConsoleLogger();
        AbstractLogger error = new ErrorLogger();
        AbstractLogger file = new FileLogger();
        AbstractLogger mylogger = new MyLogger();

        logger.setNextLogger(error);
        error.setNextLogger(file);
        file.setNextLogger(mylogger);

        // 写一条日志, 日志级别高于或者等于指定级别的日志器才需要写, 低于指定级别的日志器不需要写
        logger.logMessage("jack's doudou is a big bad guy"
                , AbstractLogger.ALL);
    }
}

abstract class AbstractLogger{

    public static int CONSOLE = 3;
    public static int ERROR = 2;
    public static int FILE = 1;
    public static int ALL = Integer.MIN_VALUE;

    private int level = 0;

    AbstractLogger nextLogger;

    public void setNextLogger(AbstractLogger nextLogger){
        this.nextLogger = nextLogger;
    }

    public int getLevel(){
        return level;
    }

    public void setLevel(int level){
        this.level = level;
    }

    public AbstractLogger getNextLogger(){
        return nextLogger;
    }

    void logMessage(String msg, int level) {
        if (this.getLevel() >=  level) {
            write(msg);
        }
        if(nextLogger != null ){
            nextLogger.logMessage(msg, level);
        }
    }

    // 是logmessage的底层支持
    abstract void write(String msg);
}

class ConsoleLogger extends AbstractLogger {

    int level = AbstractLogger.CONSOLE;
    public ConsoleLogger(){
    }

    @Override
    public int getLevel(){
        return level;
    }

    @Override
    public void setLevel(int level){
        this.level = level;
    }

    void write(String msg) {
        System.out.println("[CONSOLE] " + msg);
    }
}


class ErrorLogger extends AbstractLogger {

    int level = AbstractLogger.ERROR;

    @Override
    public int getLevel(){
        return level;
    }

    @Override
    public void setLevel(int level){
        this.level = level;
    }

    public ErrorLogger(){
    }

    void write(String msg) {
        System.out.println("[ERROR] " + msg);

    }
}


class FileLogger extends AbstractLogger {
    @Override
    public int getLevel(){
        return level;
    }

    @Override
    public void setLevel(int level){
        this.level = level;
    }

    int level = AbstractLogger.FILE;

    public FileLogger(){
    }

    void write(String msg) {
        System.out.println("[FILE] " + msg);
    }
}

class MyLogger extends AbstractLogger {

    int level = 1;

    @Override
    public int getLevel(){
        return level;
    }

    @Override
    void write(String msg){
        System.out.println("输出到ActiveMQ消息队列中: " + msg);
        System.out.println("然后: ");
        System.out.println("写在我自己的小本本上: " + msg);
    }
}