13-CHAIN-OF-RESPONSIBILITY

FGJ: Create:2024/01/27 Update: (2024-10-24)

责任链模式 #

描述 #
顾名思义，责任链模式（Chain of Responsibility Pattern）为请求创建了一个接收者对象的链。这种模式给予请求的类型，对请求的发送者和接收者进行解耦。这种类型的设计模式属于行为型模式。

在这种模式中，通常每个接收者都包含对另一个接收者的引用。如果一个对象不能处理该请求，那么它会把相同的请求传给下一个接收者，依此类推。
我们创建抽象类 AbstractLogger，带有详细的日志记录级别。然后我们创建三种类型的记录器，都扩展了 AbstractLogger。每个记录器消息的级别是否属于自己的级别，如果是则相应地打印出来，否则将不打印并把消息传给下一个记录器。
UML #

代码实现 #

public class Main {
    private static AbstractLogger getChainOfLoggers(){

        AbstractLogger debugLogger = new DebugLogger(AbstractLogger.DEBUG);
        AbstractLogger infoLogger = new InfoLogger(AbstractLogger.INFO);
        AbstractLogger errorLogger = new ErrorLogger(AbstractLogger.ERROR);

        debugLogger.setNextLogger(infoLogger);
        infoLogger.setNextLogger(errorLogger);

        return debugLogger;
    }

    public static void main(String[] args) {
        AbstractLogger loggerChain = getChainOfLoggers();

        loggerChain.logMessage(AbstractLogger.DEBUG, "This is a debug level information.");

        loggerChain.logMessage(AbstractLogger.INFO, "This is an info level information.");

        loggerChain.logMessage(AbstractLogger.ERROR, "This is an error level information.");
    }
}

public abstract class AbstractLogger {
    public static int DEBUG = 1;
    public static int INFO = 2;
    public static int ERROR = 3;

    protected int level;

    //责任链中的下一个元素
    protected AbstractLogger nextLogger;

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

    public void logMessage(int level, String message){
        if(this.level >= level){
            write(message);
        }
        if(nextLogger != null){
            nextLogger.logMessage(level, message);
        }else{ System.out.println();}
    }

    abstract protected void write(String message);
}

public class DebugLogger extends AbstractLogger {

    public DebugLogger(int level){
        this.level = level;
    }

    @Override
    protected void write(String message) {
        System.out.println("Debug::Logger: " + message);
    }
}

public class InfoLogger extends AbstractLogger {

    public InfoLogger(int level){
        this.level = level;
    }

    @Override
    protected void write(String message) {
        System.out.println("Info::Logger: " + message);
    }
}

public class ErrorLogger extends AbstractLogger {

    public ErrorLogger(int level){
        this.level = level;
    }

    @Override
    protected void write(String message) {
        System.out.println("Error::Logger: " + message);
    }
}

Reference #
- https://www.runoob.com/design-pattern/chain-of-responsibility-pattern.html

13-CHAIN-OF-RESPONSIBILITY

责任链模式 #

描述 #

UML #

代码实现 #

Reference #