Java design mode command pattern and function in Java

The command pattern belongs to the behavior pattern of the object. Command mode is also known as action mode or trading (Transaction) mode.

The command pattern encapsulates a request or operation into an object. The command mode allows the system to parameterize the client using different requests, queue requests, or log request logs, which can provide undo and redo functions for the command.

Structure of the command pattern

　　The command pattern is the encapsulation of the command. The command mode divides the responsibility for issuing the command and the responsibility for executing the command, delegating it to different objects.

Each command is an action: the requesting party makes a request to perform an action, the receiving party receives the request, and executes the action. The command pattern allows the requesting party and the receiving party to be independent, so that the requesting party does not have to know the interface of the party receiving the request, not to know how the request was received, and whether the operation was executed, when it was executed, and how it was executed.

The command allows the requesting party and the party receiving the request to evolve independently, with the following advantages:

(1) The command mode makes it easy to add new commands to the system.

(2) Allow the party receiving the request to decide whether to veto the request.

(3) It is easier to design a command queue.

(4) The revocation and recovery of the request can be easily achieved.

(5) If required, it is easier to log commands into the logs.

Advantages of the Command mode

more loosely coupled

　　The command pattern completely decouples the object that originated the command-the client, and the object that implements the command-that is, the object that initiated the command is completely unaware of who the implementation object is and how it is implemented.

more dynamic Control

　　The command mode encapsulates the request, and it can be parameterized, queued and journaled dynamically, which makes the system more flexible.

It's a natural compound command.

Command objects in command mode can be easily combined into composite commands, which are macro commands, making the system easier to operate and more powerful.

Better Extensibility

Since the object that initiated the command is fully decoupled from the specific implementation, it is easy to extend the new command, just implement the new command object, then set the specific implementation object to the Command object when assembling, and then you can use the command object, and the existing implementation does not have to change at all.

Original link http://www.cnblogs.com/java-my-life/archive/2012/06/01/2526972.html

Java design mode command pattern and function in Java