Example appreciated command mode and

First, what is? effect

1. Mode Command "request" encapsulated into objects, to use a different request queue logs or other objects, then the parameters, since the command mode is also supported undone action

2. encapsulates the request into a command object, the specific command executed by the execution request of the recipient;

effect:

　　Decoupling the sender of the command executor ;

　　Each command is an operation

Class 3. FIG.

The Invoke (caller): The caller is responsible for command execution

The Command (Command Interface): responsible packaged into a unified operation method

Concreatecommand (command implementation class): responsible for the operation command to encapsulate the true executor

Receiver real executor command: (the recipient)

Second, the example

Code Scene: manufacturers to provide a remote control, the remote control has a switch button, you need to add this remote control different electrical appliances, such as: light, fan, air conditioning, the door

Code Analysis: The electrical command mode operation request encapsulated into objects

 

Real executor command: Light

/ ** 
 * Light (Receiver) actually executed by the command
  * / 
public  class Light { 

    public  void ON () { 
        System.out.println ( "lights" ); 
    } 

    public  void OFF () { 
        System.out.println ( "lights" ); 
    } 
}

 

 Command Interface: There are two buttons above operation, of course, you can also add other operations, such as: undo

/ ** 
 * command interface 
 * / 
public  interface the Command {
     void Execute (); 
}

The turn-on request command encapsulated in the object, if an operation of the other electrical command may be packaged as objects

/ ** 
 * turn-on command ( LinghtOnCommand ) 

* /  
public  class LinghtOnCommand the implements the Command { 
　　Private Light Light; // used herein decoupling delegate

　　public LinghtOnCommand (Light Light) { the this .light = Light;} 
　　
　　@Override 
　　public  void Execute () { light.on () ;} 
}

(Remote Control) command to the caller: the install command on the remote control, while providing pressing the button, the command is executed

/ ** 
 * remote 
 * command caller Invoke 
 * / 
public  class the CommandController {
     Private the Command SOLT; 

    public  void the setCommand (the Command Command) { 
        SOLT = Command; 
    } 

    / ** 
     * remote control button pressed 
     * / 
    public  void buttonWasPressed () { 
        solt.execute (); 
    } 
}

The client calls:

/ ** 
 * test client 
 * / 
public  class MainClient { 

    public  static  void main (String [] args) { 
        the CommandController the CommandController = new new the CommandController (); 
        Light Light = new new Light (); 
        LinghtOnCommand linghtOnCommand = new new LinghtOnCommand (Light); 

        the CommandController .setCommand (linghtOnCommand); 
        commandController.buttonWasPressed (); 
    } 
} 

// console display 
lights

Third, the summary

1. Summary

• The command mode request objects (the CommandController) and performs the requested object Decoupling
• Invoke the command object's execute (), the action will make the recipient will be executed
• Command mode is also supported revocation , the practice is to implement an undo command, returned execute () state before being executed

2. More use command mode:

• Queue request: a command taken out from the queue, calls its Execute (), wait for the call is completed, a command to discard the object, and then remove a command
• Log request
• Undo previous operation: Transaction
• Thread Pool
• 。。。