getservlet.java

本程序使用ajax技术实现聊天室程序.使用ajax动态获取聊天记录.

package book.chat;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Vector;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import book.chat.table.MessageEO;
import book.chat.table.UserEO;

public class GetServlet extends HttpServlet{
	public void doPost(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, java.io.IOException {
		boolean bSuccess = true;
		String chatID = request.getParameter("chatId");
		String lastID = request.getParameter("last");
		
		if ( chatID==null||chatID.equals("") )
			return ;
		if ( lastID==null||lastID.equals("") )
			return ;
		
		Vector vResult = new Vector();
		String sql = "select message_id from message where chat_id="+chatID+" and message_id >"+lastID;
		try {
			MessageEO message =null;
			ResultSet rs = DbManager.getResultSet( sql );
			while (rs.next())
			{
				message = new MessageEO(rs.getInt("MESSAGE_ID"));
				vResult.add(message);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		DbManager.releaseConnection();
		
		response.setContentType("text/xml");//设置返回数据类型为xml格式
		java.io.PrintWriter out = response.getWriter();
		System.out.println(parasToXML(vResult));
		out.print(parasToXML(vResult));//调用parasToXML()方法
	}

public void doGet(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, java.io.IOException {

doPost(request, response);
}
public String parasToXML(Vector v) {// 该方法将数据转化成XML格式输出
	StringBuffer buf = new StringBuffer();
	buf.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
	buf.append("<root>");
	for (int i = 0; i < v.size(); i++) {
		MessageEO message = (MessageEO) v.get(i);
		buf.append("<message id=\""+message.getMessageID()+"\">");
		buf.append("<user>" + message.getUserName() + "</user>");
		buf.append("<text>" + message.getMessage() + "</text>");
		buf.append("<time>" + message.getPostTime()+ "</time>");
		buf.append("</message>");
	}
	buf.append("</root>");
	return buf.toString();
}

}