二月三日

　　今日将ajax中的动态后台验证重复添加写出来了

一

　　动态验证主要就是运用了ajax异步处理验证运用josn数据类型

$(function(){
	


	$("#id").blur(function(){
		var usernameInput=$("#id").val;
		$.post(
				"chakan",
				{"username":usernameInput},
				function(data){
					var isExist = data.isExist;
					//3、根据返回的isExist动态的显示信息
					var usernameInfo = "";
					if(isExist){
						//该用户存在
						usernameInfo = "该用户名可以使用";
						alert("1");
						$("#usernameInfo").css("color","red");
					}else{
						usernameInfo = "该用户名已经存在"
							alert("2");
						$("#usernameInfo").css("color","green");
					}
					$("#span1").html(usernameInfo);
					
				},
				"json"
		
		
		
		
		);
		
		
	});
	
	
});

　　后台主要是

package servlet;

import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

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

import DBUtil.DBUtil;
import bean.user;

/**
 * Servlet implementation class chakan
 */
@WebServlet("/chakan")
public class chakan extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public chakan() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		
	String username=request.getParameter("username");
	System.out.println("username");
	String sql="select * from user where JobID='"+username+"'";
	boolean flag=false;
	 Connection conn=DBUtil.getConn();
		Statement state=null;
		ResultSet rs=null;
		List<user>list=new ArrayList<>();
		try {
			state = conn.createStatement();
			rs = state.executeQuery(sql);
			//要用statement类的executeQuery()方法来下达select指令以查询数据库，
			//executeQuery()方法会把数据库响应的查询结果存放在ResultSet类对象中供我们使用。
			while (rs.next()){
			
					
	flag=true;
	
				 
				
				
			}
		}
		catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBUtil.close(rs, state, conn);
		}
	response.getWriter().write("{"flag":"+flag+"}");
	
	
	}

	/**
	 * @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);
	}

}

　　效果图