使用命令设计模式 [英] Using Command Design pattern

问题描述

任何一个人都可以用简单的命令模式来解释。我在互联网上引用，但我感到困惑。

解决方案

  public interface Command {
 public void execute（）; 
} 
  

在大多数情况下，命令是不可变的，包含封装单个操作的指令这是按需执行的。您可能还有一个RuntimeCommand在执行时接受指令，但是根据实施情况，您可以深入了解策略或装饰器模式。

在我自己的看来，我认为非常重要的是注意命令的不变的上下文，否则命令成为一个建议。例如：

  public final class StopServerCommand实现Command {
 private final Server server; 
 
 public StopServerCommand（服务器服务器）{this.server = server; } 
 
 public void execute（）{
 if（server.isRunning（））server.stop（）; 
} 
} 
 
 public class Application {
 // ... 
 public void someMethod（）{
 stopButton.addActionListener ActionListener（）{
 public void actionPerformed（Event e）{
 stopCommand.execute（）; 
} 
}）; 
} 
} 
  

我个人并不喜欢命令。在我自己的经验中，他们只对框架回调有效。

如果有帮助，想一个隐喻意义上的命令;训练有素的士兵由他/她的指挥官指挥，并且要求士兵执行这个命令。

Can any one explain with simple example of Command Pattern. I refer in internet but i got confused.

解决方案

public interface Command {
   public void execute();
}

For the most part, commands are immutable and contain instructions that encapsulate a single action that is executed on demand. You might also have a RuntimeCommand that accepts instructions upon execution, but this delves more into the Strategy or Decorator Patterns depending on the implementations.

In my own opinion, I think it's very important to heed the immutable context of a command otherwise the command becomes a suggestion. For instance:

public final class StopServerCommand implements Command {
    private final Server server;

    public StopServerCommand(Server server) { this.server = server; }

    public void execute() {
        if(server.isRunning()) server.stop();
    }
}

public class Application {
    //...
    public void someMethod() {
        stopButton.addActionListener(new ActionListener() {
            public void actionPerformed(Event e) {
                 stopCommand.execute();
            }
        });
    }
}

I personally don't really like commands. In my own experience, they only work well for framework callbacks.

If it helps, think of a command in a metaphorical sense; a trained soldier is given a command by his/her commanding officer, and on demand the soldier executes this command.

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