需求
通过ajax异步刷新页面验证用户输入的账号密码是否在数据库中存在。
技术栈
JSP+Servlet+Oracle
具体代码
JSP部分：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><script> function createXMLHttpRequest() { try { xmlHttp = new XMLHttpRequest();//除了ie之外的其他浏览器使用ajax } catch (tryMS) { try { xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");//ie浏览器适配 } catch (otherMS) { try { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");//ie浏览器适配 } catch (failed) { xmlHttp = null; } } } return xmlHttp; } //提交请求 var xmlHttp; function checkUserExists() { var u = document.getElementById("uname"); var username = u.value; if (username == "") { alert("请输入用户名"); u.focus(); return false; } //访问字符串 var url = "loginServlet"; //创建核心xmlhttprequest组件 xmlHttp = createXMLHttpRequest(); //设置回调函数 xmlHttp.onreadystatechange = proessRequest; //初始化核心组件 xmlHttp.open("post", url, true); //设置请求头 xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded;"); //发送请求 xmlHttp.send("uname="+username); } //回调函数 function proessRequest() { if (xmlHttp.status==200 && xmlHttp.readyState == 4) { var b = xmlHttp.responseText;//得到服务端的输出结果 if (b=="true") { document.getElementById("alert").innerHTML = "<font color='red'>用户名已经存在！</font>"; }else { document.getElementById("alert").innerHTML = "<font color='blue'>用户名可以使用！</font>"; } } }</script><body> 请输入用户名： <input id="uname" name="uname" type="text" onblur="checkUserExists()" /><div id="alert" style="display:inline"></div></body></html> 这里没有用Dao层，直接用servlet和service层进行验证。
下面是service下JDBC查询的代码：
import java.sql.Connection;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import com.stx.service.User;import com.stx.service.ConnectionManager;public class ajaxService { public boolean searchUser (String uname) { //jdbc查询用户名是否存在 boolean isFalse = false; Connection connection = null; Statement stmt = null; ResultSet rs = null; connection = ConnectionManager.getConnection(); try { stmt = connection.createStatement(); String sql = "select * from user_b where uname='"+uname+"'";//sql语句 rs = stmt.executeQuery(sql); isFalse=rs.next(); } catch (SQLException e) { e.printStackTrace(); } finally { ConnectionManager.closeResultSet(rs); ConnectionManager.closeStatement(stmt); ConnectionManager.closeConnection(connection); } return isFalse; }} JDBC连接代码：
import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;public class ConnectionManager { private final static String DRIVER_CLASS = "oracle.jdbc.OracleDriver"; private final static String URL = "jdbc:oracle:thin:@localhost:1521:orcl"; private final static String DBNAME = "ibook"; private final static String PASSWORD = "qwer"; public static Connection getConnection() { Connection connection = null; try { Class.forName(DRIVER_CLASS); connection = DriverManager.getConnection(URL, DBNAME, PASSWORD); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } return connection; } public static void closeResultSet(ResultSet rs) { try { if (rs != null) rs.close(); } catch (SQLException e) { e.printStackTrace(); } } public static void closeConnection(Connection connection) { try { if (connection != null && !connection.isClosed()) connection.close(); } catch (SQLException e) { e.printStackTrace(); } } public static void closeStatement(Statement stmt) { try { if (stmt != null) stmt.close(); } catch (SQLException e) { e.printStackTrace(); } }} 关于user类：
public class User { private String uname; public User() { super(); } public User(String uname) { super(); this.uname = uname; } public String getUname() { return uname; } public void setUname(String uname) { this.uname = uname; } 关于控制层servlet：
import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.stx.service.ajaxService;/** * Servlet implementation class loginServlet */public class loginServlet extends HttpServlet { private static final long serialVersionUID = 1L; private ajaxService ajaxService = new ajaxService(); /** * @see HttpServlet#HttpServlet() */ public loginServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); String uname = request.getParameter("uname");//获取到输入的用户名 boolean isUname = ajaxService.searchUser(uname);//调用service中的查询方法 response.setCharacterEncoding("UTF-8");//设置字符编码 PrintWriter out = response.getWriter(); out.print(isUname); out.flush(); out.close();//关闭资源 } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); }} 以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持VeVb武林网。
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