编写此Java代码的更好方法是什么？

Question

public void handleParsedCommand(String[] commandArr) {
    if(commandArr[0].equalsIgnoreCase("message")) {
        int target = Integer.parseInt(commandArr[1]);
        String message = commandArr[2];
        MachatServer.sendMessage(target, this.conId, message);
    } else if(commandArr[0].equalsIgnoreCase("quit")) {
        // Tell the server to disconnect us.
        MachatServer.disconnect(conId);
    } else if(commandArr[0].equalsIgnoreCase("confirmconnect")) {
       // Blah blah and so on for another 10 types of command
    } else {
        try {
            out.write("Unknown: " + commandArr[0] + "\n");
        } catch (IOException e) {
            System.out.println("Failed output warning of unknown command.");
        }
    }
}

我有这部分服务器代码用于处理消息类型.每条消息都包含其中的类型commandArr[0]和参数commandArr[].然而,这个当前的代码,虽然工作似乎非常不优雅.有没有更好的方法来处理它？(据我所知,String价值不能用于switch陈述,即使这样,switch陈述也只是一个很小的改进.

Answer 1

我会使用Command Design Pattern重构它.

基本上,您的每个命令,消息,退出,确认连接和默认都将具有类实现,并将实现命令接口.

/*the Command interface*/
public interface ICommand {
    void execute(String[] commandArr);
}

public class Message implements ICommand {
    void execute(String[] commandArr) {
        int target = Integer.parseInt(commandArr[1]);
        String message = commandArr[2];
        MachatServer.sendMessage(target, this.conId, message);
    }
}

//same type of class for other commands

public class CommandManager {
    public ICommand getCommand(String commandName) {
        //store all the commands in a hashtable. 
        //Pull them out by name as requested.
    }

    //Esko's suggestion from comments
    public static void executeImmediately(String[] commandArr) {
        getCommand(commandArr[0]).execute(commandArr);
    }
}


public void handleParsedCommand(String[] commandArr) {

    ICommand command = CommandManager.getCommand(commandArr[0]);
    command.execute(commandArr);

//or Esko

    CommandManager.executeImmediately(commandArr);

}

Answer 2

以下是使用枚举的两个变体(几乎)以更易读的方式提供相同的行为:

1)类型安全开关的枚举:

enum CommandType {
MESSAGE,
QUIT,
CONFIRMCONNECT
}

public void handleParsedCommand(String[] commandArr) {
    CommandType cmd = null;

    try {
        cmd = CommandType.valueOf(commandArr[0].toUpperCase());
    } catch (IllegalArgumentException e) {
        // this kind of error handling, seems a bit strange, by the way.
        try {
            out.write("Unknown: " + commandArr[0] + "\n");
        } catch (IOException e) {
           System.out.println("Failed output warning of unknown command.");
        }
        return;
    }
    switch(cmd) {
        case MESSAGE:
            int target = Integer.parseInt(commandArr[1]);
            String message = commandArr[2];
            MachatServer.sendMessage(target, this.conId, message);
        case QUIT:
            // Tell the server to disconnect us.
            MachatServer.disconnect(conId);
        case CONFIRMCONNECT:
            // Blah blah and so on for another 10 types of command
        }
    }
}

主要的好处是代码更具可读性,但是您避免为每种情况创建新的方法或类,如果处理代码只有一行或两行,则不允许创建新的方法或类.

2)另一个基于枚举的变体,实际上是一个Command模式,但它有很多膨胀代码:

enum CommandType {
    MESSAGE {
        void execute(CommandProcessor cp, String[] params) {
            int target = Integer.parseInt(params[1]);
            String message = params[2];
            MachatServer.sendMessage(target, cp.conId, message);        
        }
    },
    QUIT {
        void execute(CommandProcessor cp, params param) {
            MachatServer.disconnect(cp.conId);  
        }
    },
    CONFIRMCONNECT {
        void execute(CommandProcessor cp, params param) {
              // Blah blah and so on for another 10 types of command
        }
    };

    abstract void execute(CommandProcessor cp, String[] param);
}
public void handleParsedCommand(String[] commandArr) {
    CommandType cmd = null;

    try {
        cmd = CommandType.valueOf(commandArr[0].toUpperCase());
    } catch (IllegalArgumentException e) {
        try {
            out.write("Unknown: " + commandArr[0] + "\n");
        } catch (IOException e) {
            System.out.println("Failed output warning of unknown command.");
        }
        return;
    }
    cmd.execute(this, commandArr);
}