简易聊天程序教程（一）自定义异常和消息格式

举一个请求消息的例子：

       from:wapoonx

       to:xwp

       command:send

       hello

以上就是一个发送消息的请求，from字段表明这个消息是从谁发送过来的。to这个字段表明要发送给谁，也就是接收方是谁。command这个字段表明要执行的命令。以一个空行为标志。隔开正文和头部字段。在这个例子中正文是hello。服务器会根据command字段，从请求报文中选取自己想要的信息。

举一个响应消息的例子：

code:0

description:success

（注意这里是空的正文）

package SimpleChat;
import java.util.Map;
import java.util.TreeMap;

public class RequestMessage {
	private String from = "";
	private String to = "";
	private String command = "";
	private String rawContext = "";
	
	public RequestMessage() {
		
	}
	
	public RequestMessage(String raw) {
		parse(raw);
	}
	
	public String getFrom() {
		return from;
	}
	
	public String getTo() {
		return to;
	}
	
	public String getCommand() {
		return command;
	}
	
	public String getContext() {
		return rawContext;
	}
	
	public void setFrom(String f) {
		from = f;
	}
	
	public void setTo(String to) {
		this.to = to;
	}
	
	public void setCommand(String cmd) {
		this.command = cmd;
	} 
	
	public void setContext(String con) {
		rawContext = con;
	}
	
	public String Format() {
		String res = "from:" + from+ "\r\n";
		res += "to:" + to + "\r\n";
		res += "command:" + command + "\r\n\r\n";
		res += rawContext;
		
		return res;
	} 
	
	private void parse(String raw) {
		String[] temp = raw.split("\r\n\r\n");
		String[] fields = temp[0].split("\r\n");
		
		if (temp == null || fields == null) {
			return ;
		}
		
		for (int i = 0; i < fields.length; ++i) {
			if (fields[i].indexOf("from:") == 0) {
				from = fields[i].substring("from:".length());
			}
			else if (fields[i].indexOf("to:") == 0) {
				to = fields[i].substring("to:".length());
			}
			else if (fields[i].indexOf("command:") == 0) {
				command = fields[i].substring("command:".length());
			}
		}
		if (temp.length == 2) {
			rawContext = temp[1];			
		}
	}
	
	
	public static Map<String, String> parseContext(String rawContext) throws ChatMessageException {
		if (rawContext == null || rawContext.equals("")) {
			return new TreeMap<String, String>();
		}
		
		Map<String, String> context = new TreeMap<String, String>();
		String[] temp = rawContext.split("\r\n");
		
		for (int i = 0; i < temp.length; ++i) {
			String[] res = temp[i].split(":");
			if (res.length == 2) {
				context.put(res[0], res[1]);				
			} else {
				throw new ChatMessageException("response message is invaild. context's format error"); 
			}
		}
		
		return context;
	}
	
	public Map<String, String> parseContext() throws ChatMessageException {
		return parseContext(this.rawContext);
	}
}