浅谈JAVA 责任链模式

public abstract class AbstractLogger {
  public static int INFO = 1;
  public static int DEBUG = 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);
   }
  }
 
  abstract protected void write(String message);
  
}

public class ConsoleLogger extends AbstractLogger {
 
  public ConsoleLogger(int level){
   this.level = level;
  }
 
  @Override
  protected void write(String message) {  
   System.out.println("Standard Console::Logger: " + message);
  }
}

public class ErrorLogger extends AbstractLogger {
 
  public ErrorLogger(int level){
   this.level = level;
  }
 
  @Override
  protected void write(String message) {  
   System.out.println("Error Console::Logger: " + message);
  }
}

public class FileLogger extends AbstractLogger {
 
  public FileLogger(int level){
   this.level = level;
  }
 
  @Override
  protected void write(String message) {  
   System.out.println("File::Logger: " + message);
  }
}

public class ChainPatternDemo {
  
  private static AbstractLogger getChainOfLoggers(){
 
   AbstractLogger errorLogger = new ErrorLogger(AbstractLogger.ERROR);
   AbstractLogger fileLogger = new FileLogger(AbstractLogger.DEBUG);
   AbstractLogger consoleLogger = new ConsoleLogger(AbstractLogger.INFO);
 
   errorLogger.setNextLogger(fileLogger);
   fileLogger.setNextLogger(consoleLogger);
 
   return errorLogger; 
  }
 
  public static void main(String[] args) {
   AbstractLogger loggerChain = getChainOfLoggers();
 
   loggerChain.logMessage(AbstractLogger.INFO, "This is an information.");
 
   loggerChain.logMessage(AbstractLogger.DEBUG, 
     "This is a debug level information.");
 
   loggerChain.logMessage(AbstractLogger.ERROR, 
     "This is an error information.");
  }
}