Ajax（6） Ajax向servlet请求数据库操作 并显示到当前页面 这个未经测试

假设：
1、你的页面在Web-Root下，内容为：  <div id="showMsg"></div><input type="text" id="userName" />，所用编码为utf-8
2、你的servlet为：  HelloWorldServlet.java  映射路径为   servlet/helloWorldServlet
步骤：
1、引入jquery-1.6.4.min.js
2、编写id为userName的输入框的点击触发函数：
      $("#userName").keyup(function(){
            $.ajax({
                  type: "post",
                  url: "servlet/helloWorldServlet?userName="+$(this).val(),
                  dataType: "json",
                  success: function(data){
                        $("#showMsg").html(data.msg);//修改id为showMsg标签的html
                  }, error: function(){
                        alert("请求出错");
                  }
            })
      })
3、后台处理接收到的内容：
      request.setCharactorEncoding("utf-8");
      String userName = request.getParameter("userName");
      response.setCharactorEncoding("utf-8");
      PringWriter out = response.getWriter();
      out.print("{\"msg\":\"你好~~"+userName+"!\"}");

注意事项：
1、这里的编码统一为utf-8
2、请求路径servlet/helloWorldServlet为相对路径，因此你的页面必须在项目的Web-Root下（也就是默认的web文件夹下，名字可能因项目配置不同而改变）
3、没了，记得给分哦，打字很辛苦的~

servlet返回ajax请求数据

未来几年，程序员都应该这样写简历  

问题描述: 在前台(jsp)用ajax提交数据, 后台(servlet)处理后返回"1"或者"0". 可是前台获得的返回数据是长度为3的字符串, 即"1__"或"0__"(_表示一个空白字符).

环境:  tomcat-7.0.29 + MySQL 5.5 + jquery 1.7

其他: 以为是UTF-8 + BOM的问题, 可是把所有文件都改为UTF-8了,问题依旧.

这是后台处理请求的Validate.java文件

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import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.sql.*;   public class Validate extends HttpServlet {     public void doGet(HttpServletRequest request, HttpServletResponse response)         throws IOException, ServletException {             String user_name = new String(request.getParameter("userName").getBytes("ISO-8859-1"), "UTF-8");             String user_pwd = new String(request.getParameter("password").getBytes("ISO-8859-1"), "UTF-8");             PrintWriter out = response.getWriter();             String driver = "com.mysql.jdbc.Driver";             String dbUser = "root";             String dbPwd = "3306";             String db = "appbase";             String url = "jdbc:mysql://localhost:3306/" + db + "?user=" + dbUser + "&password=" + dbPwd;             ResultSet rs = null;             String sqlString = "select * from client where login_account='" + user_name + "' and password='" + user_pwd + "'";             try {                 Class.forName(driver).newInstance();                 Connection conn = DriverManager.getConnection(url);                 Statement ps = conn.createStatement();                 rs = ps.executeQuery(sqlString);                 if(rs.next())                     out.println("1");                 else                     out.println("0");             } catch(ClassNotFoundException e) {                 out.println("ClassNotFoundException");             } catch(SQLException ex) {                 out.println("SQLException");             } catch(Exception exe) {                 out.println("OtherException");             }               } }

这是前台ajax提交数据的代码:

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$(document).ready(function() {         $("#_submit").click(function() {             var user_name = $("#_user_name").val();             var user_pwd = $("#_user_pwd").val();             $.ajax({                 url: "login/validate",                 data: { userName: user_name, password: user_pwd },                 type: "GET",                 datatype: "html",                 success: function(data){                     alert(data.length);                 }             });         });     });