设计模式之 责任链模式

责任链模式是一种非常有趣的模式。

责任链模式用于避免请求发送者与多个请求处理者耦合在一起，让所有请求的处理者持有下一格对象的引用，从而将请求串联成一条链，在有请求发生时，可将请求沿着这条链传递，直到遇到该对象的处理器。

（1）定义处理接口

public interface Handler{
    void operator();
}

（2）定义抽象处理类

public abstract class AbstractHandler{
    private Handler handler;
    
    public Handler getHandler() {
        return handler;
    }
    
    public void setHandler(Handler handler) {
        this.handler = handler;
    }
}

（3）定义责任类

public class AuthHandler extends AbstractHandler implements Handler{
    private final static Log logger = LogFactory.getLog(this.getClass());
    private String name;
    public AuthHandler(String name){
        this.name = name;
    }
    @Override
    public void operator(){
        logger.info("user auth...");
        if (getHandler() != null){
            getHandler().operator();
        }
    }
}

public class BusinessHandler extends AbstractHandler implements Handler{
    private final static Log logger = LogFactory.getLog(this.getClass());
    private String name;
    public BusinessHandler(String name){
        this.name = name;
    }
    @Override
    public void operator(){
        logger.info("business info handler ...");
        if (getHandler() != null){
            getHandler().operator();
        }
    }
}

public class ResponseHandler extends AbstractHandler implements Handler{
    private final static Log logger = LogFactory.getLog(this.getClass());
    private String name;
    public ResponseHandler(String name){
        this.name = name;
    }
    @Override
    public void operator(){
        logger.info("response  ...");
        if (getHandler() != null){
            getHandler().operator();
        }
    }
}

（4）使用责任链模式

public static void main(String[] args){
    AuthHandler authHandler = new AuthHandler("auth");
    BusinessHandler businessHandler = new BusinessHandler("business");
    ResponseHandler responseHandler = new ResponseHandler("response");
    authHandler.setHandler(businessHandler);
    businessHandler.setHandler(responseHandler);
}

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