ajax初级示例（下拉列表联动）

朱雀 2022-03-18 11:17 231阅读 0赞

下拉列表联动效果如下动图：

![20190220175059790.gif][]

数据库 表字段的信息

![20190220173040565.png][]![20190220173053957.png][]

**新建web项目**

jar包及js

![20190220174044139.png][]

实体对象

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25haWxuZWhj_size_16_color_FFFFFF_t_70][]

index.jsp

<%@ 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">
    <script type="text/javascript" src="js/jquery-1.11.3.min.js"></script>
    <script type="text/javascript">
    	$(function() {
    		$("#firstSelect").change(function(){
    			$.get(
    				"/ajax_test/AjaxK",
    				{atel:$("#firstSelect").val()},
    				function(data) {
    					$("#secondSelect").empty();
    					for(var i = 0; i < data.length; i++) {
    						var dataObj = data[i];
    						var $option = $("<option></option>");
    						$option.text(dataObj.aname);
    						$option.appendTo($("#secondSelect"));
    					}
    				},
    				"json"
    			);
    		});
    		
    		$.get(
    			"/ajax_test/AjaxT",
    			function(data) {
    				$("#firstSelect").empty();
    				for(var i = 0; i < data.length; i++) {
    					var dataObj = data[i];
    					var $option = $("<option></option>");
    					$option.text(dataObj.name);
    					$option.val(dataObj.num);
    					$option.appendTo($("#firstSelect"));
    				}
    			},
    			"json"
    		);
    	});
    </script>
    <title>Insert title here</title>
    </head>
    <body>
    	<div>
    		<select name="first" id="firstSelect"></select>
    		<select name="second" id="secondSelect"></select>
    	</div>
    	<table id="tabShow" border="1px">
    		<thead>
    			<tr>
    				<td>NAME</td>
    				<td>TEL</td>
    				<td>MAIL</td>
    			</tr>
    		</thead>
    		<tbody id="tableBody">
    		</tbody>
    	</table>
    </body>
    </html>

工具类

package cla.fjh.tool;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class JDBCUtil {
    	
    	static String driverClass = null;
    	static String url = null;
    	static String name = null;
    	static String password= null;
    	
    	static{
    			driverClass = "com.mysql.jdbc.Driver";
    			url = "jdbc:mysql://localhost/ajaxt";
    			name = "root";
    			password = "root";
    			
    	}
    	
    	/**
    	 * 获取连接对象
    	 * @return
    	 */
    	public static Connection getConn(){
    		Connection conn = null;
    		try {
    			Class.forName(driverClass);
    			//静态代码块 ---> 类加载了，就执行。 java.sql.DriverManager.registerDriver(new Driver());
    			//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
    			//DriverManager.getConnection("jdbc:mysql://localhost/test?user=monty&password=greatsqldb");
    			//2. 建立连接 参数一： 协议 + 访问的数据库 ， 参数二： 用户名 ， 参数三： 密码。
    			conn = DriverManager.getConnection(url, name, password);
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    		return conn;
    	}
    	
    	/**
    	 * 释放资源
    	 * @param conn
    	 * @param st
    	 * @param rs
    	 */
    	public static void release(Connection conn , Statement st , ResultSet rs){
    		closeRs(rs);
    		closeSt(st);
    		closeConn(conn);
    	}
    	public static void release(Connection conn , Statement st){
    		closeSt(st);
    		closeConn(conn);
    	}
    
    	
    	private static void closeRs(ResultSet rs){
    		try {
    			if(rs != null){
    				rs.close();
    			}
    		} catch (SQLException e) {
    			e.printStackTrace();
    		}finally{
    			rs = null;
    		}
    	}
    	
    	private static void closeSt(Statement st){
    		try {
    			if(st != null){
    				st.close();
    			}
    		} catch (SQLException e) {
    			e.printStackTrace();
    		}finally{
    			st = null;
    		}
    	}
    	
    	private static void closeConn(Connection conn){
    		try {
    			if(conn != null){
    				conn.close();
    			}
    		} catch (SQLException e) {
    			e.printStackTrace();
    		}finally{
    			conn = null;
    		}
    	}
    }

servlet类：AjaxT

package cla.fjh.ajax;
    
    import java.io.IOException;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.util.ArrayList;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.alibaba.fastjson.JSON;
    
    import cla.fjh.dao.BTest;
    import cla.fjh.tool.JDBCUtil;
    
    public class AjaxT extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		Connection conn = null;
    		PreparedStatement state = null;
    		ResultSet resultSet = null;
    		try {
    			String sql = "select * from btest;";
    			conn = JDBCUtil.getConn();
    			state = conn.prepareStatement(sql);
    			resultSet = state.executeQuery();
    			List<BTest> list = new ArrayList<BTest>();
    			while(resultSet.next()) {
    				BTest bt = new BTest(resultSet.getString("name"), resultSet.getString("num"));
    				list.add(bt);
    			}
    			String jsonString = JSON.toJSONString(list);
    			System.out.println(jsonString);
    			response.setCharacterEncoding("UTF-8");		
    			response.getWriter().print(jsonString);
    			
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

servlet类：AjaxK

package cla.fjh.ajax;
    
    import java.io.IOException;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.util.ArrayList;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.alibaba.fastjson.JSON;
    
    import cla.fjh.dao.ATest;
    import cla.fjh.tool.JDBCUtil;
    
    public class AjaxK extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		Connection conn = null;
    		PreparedStatement state = null;
    		ResultSet resultSet = null;
    		String atel = request.getParameter("atel");
    		try {
    			String sql = "select * from atest where atel = " + atel;
    			conn = JDBCUtil.getConn();
    			state = conn.prepareStatement(sql);
    			resultSet = state.executeQuery();
    			List<ATest> list = new ArrayList<ATest>();
    			while(resultSet.next()) {
    				ATest at = new ATest(resultSet.getString("aname"), resultSet.getString("atel"),resultSet.getString("amail"));
    				list.add(at);
    			}
    			String jsonString = JSON.toJSONString(list);
    			response.setCharacterEncoding("UTF-8");		
    			response.getWriter().print(jsonString);
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

web.xml

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25haWxuZWhj_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25haWxuZWhj_size_16_color_FFFFFF_t_70 2][]

[20190220175059790.gif]: /images/20220318/d9e4c409f8234ca394829abcb60a68dc.png
[20190220173040565.png]: https://img-blog.csdnimg.cn/20190220173040565.png
[20190220173053957.png]: /images/20220318/f927c85734db4152bd72d95001dd5f69.png
[20190220174044139.png]: /images/20220318/98ebe7a14b14484bb89e164e26a14927.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25haWxuZWhj_size_16_color_FFFFFF_t_70]: /images/20220318/b9513db9234c4c87865befc04a020946.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25haWxuZWhj_size_16_color_FFFFFF_t_70 1]: /images/20220318/f79141152a094b1ba924380812b5ba15.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25haWxuZWhj_size_16_color_FFFFFF_t_70 2]: /images/20220318/9e1ec127213441689da48d12ca8d03e8.png