AJAX用于判定用户是否注册

    
 用户ID 
 姓名：
 密码：

 import java.io.IOException; import java.io.PrintWriter; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class CheckServlet extends HttpServlet{ public static final String DBDRIVER = "oracle.jdbc.OracleDriver"; public static final String DBURL = "jdbc:oracle:thin:@59.173.240.149:1521:heer"; public static final String DBUSER = "hnsyu_dev"; public static final String DBPASS = "hnsyuok"; public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ this.doPost(request, response); } public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ request.setCharacterEncoding("gbk"); response.setContentType("text/html"); Connection connection = null; PreparedStatement preparedStatement = null; ResultSet resultSet = null; PrintWriter out = response.getWriter(); String userid = request.getParameter("userid"); try { Class.forName(DBDRIVER); connection = DriverManager.getConnection(DBURL, DBUSER, DBPASS); String sql = "select count(userid) from userdemo where userid=?"; preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1,userid); resultSet = preparedStatement.executeQuery(); if (resultSet.next()) { if(resultSet.getInt(1)>0){ out.print("false"); System.out.println("true"); }else { out.print("false"); } } out.close(); } catch (Exception e) { e.printStackTrace(); }finally{ try { connection.close(); } catch (Exception e) { e.printStackTrace(); } } } } 

    index.jsp CheckServletCheckServlet CheckServlet/CheckServlet