Java Design Patterns Tutorial - Java Design Pattern - Chain of Responsibility Pattern

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The chain of responsibility pattern creates a list of receiver objects for a request.

This pattern is behavioral patterns.

When using chain of responsibility pattern, normally each receiver contains reference to another receiver.

If one object cannot handle the request then it passes the same to the next receiver and so on.

Example

abstract class Logger {
   protected Logger nextLogger;
//from  w  w  w.j  a v  a 2  s. c o m
   public void setNextLogger(Logger nextLogger){
      this.nextLogger = nextLogger;
   }

   public void logMessage(String message){
      log(message);
      if(nextLogger !=null){
         nextLogger.logMessage(message);
      }
   }
   abstract protected void log(String message);  
}
class ConsoleLogger extends Logger {
   public ConsoleLogger(){
   }
   @Override
   protected void log(String message) {    
      System.out.println("Console::Logger: " + message);
   }
}
class EMailLogger extends Logger {
   public EMailLogger(){
   }
   @Override
   protected void log(String message) {    
      System.out.println("EMail::Logger: " + message);
   }
}
class FileLogger extends Logger {
   public FileLogger(){
   }
   @Override
   protected void log(String message) {    
      System.out.println("File::Logger: " + message);
   }
}
public class Main {  
   private static Logger getChainOfLoggers(){
      Logger emailLogger = new EMailLogger();
      Logger fileLogger = new FileLogger();
      Logger consoleLogger = new ConsoleLogger();
      emailLogger.setNextLogger(fileLogger);
      fileLogger.setNextLogger(consoleLogger);
      return emailLogger;  
   }
   public static void main(String[] args) {
      Logger loggerChain = getChainOfLoggers();
      loggerChain.logMessage("Null pointer");
      loggerChain.logMessage("Array Index Out of Bound");
      loggerChain.logMessage("Illegal Parameters");
   }
}

The code above generates the following result.

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