loginservlet.java

用java编写的网页基于Ajax的应用

package book.servlet;

import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import book.portal.*;
import book.portal.table.UserEO;

public class LoginServlet extends HttpServlet {
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, java.io.IOException {
		boolean bSuccess = true;// 判断是否登陆成功的标记
		String errMessage = "";// 显示错误消息
		UserEO user = null;// 定义一个UserEO对象
		String name = request.getParameter("userName");// 获得用户名的值
		String password = request.getParameter("passWord");// 获得密码的值
		if (name == null || name.trim().equals(""))// 判断用户名是否为空
		{
			bSuccess = false;
			errMessage = "Please enter user name";
		}else{//如果不为空则查询数据库中是否存在该用户
			String strSQL = "select user_id from ajax_user where user_name='"+ name+"'";		
			try {
				ResultSet rs = DbManager.getResultSet(strSQL);
				rs.last();
				int row = rs.getRow();
				if (row!=1)
				{
					bSuccess=false;
					errMessage = "This user name is not exist";
				}
			} catch (SQLException e) {
				bSuccess = false;
			}
		}
		if (bSuccess && (password == null || password.trim().equals("")))// 判断密码是否为空
		{
			bSuccess = false;
			errMessage = "Please enter password";
		}
		if (bSuccess)// 如果都不为空，则查询数据库
		{
			// 查询的sql语句
			String strSQL = "select user_id from ajax_user where user_name='"
					+ name + "' and password='" + password + "'";
			try {
				ResultSet rs = DbManager.getResultSet(strSQL);// 获得一个记录集
				rs.last();// 移动到最后一行
				int row = rs.getRow();// 获得总的记录数
				if (row == 1)// 如果只找到一条记录，则表示找到该对应的用户
				{
					user = new UserEO(rs.getInt("USER_ID"));// 实例化该用户
					HttpSession session = ((HttpServletRequest) request)
							.getSession(true);
					session.setAttribute("user", user.getId()+"");// 设置session;
				} else {// 如果没找到该用户
					bSuccess = false;
					errMessage = "Invalid password!";
				}
			} catch (SQLException e) {
				bSuccess = false;
				errMessage = "Invalid user name or password!";
			}
		}
		if (bSuccess)// 如果登陆成功，则转向homepage.jsp页面.
		{
			RequestDispatcher dispatcher = request.getRequestDispatcher("homepage.jsp");
			dispatcher.forward(request, response);
		} else {// 如果没有登陆成功，返回错误信息
			response.setContentType("text/html");
			java.io.PrintWriter out = response.getWriter();
			out.println(errMessage);
		}
	}

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

		doPost(request, response);
	}

}