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1.实验目的

学习和掌握jQuery获取网页元素对象的格式。使用JDBC进行数据库的连接以及使用Statement对象执行SQL查询语句。掌握使用Properties类加载Properties文件中参数的方式。使用<jsp:UseBean>标签创建对象。使用$.get方法向服务器发送请求以及获取服务器中的数据。

2.实验所用方法

上机实践

3.实验步骤及截图

建立数据库表格info:

在web目录下创建index.jsp文件用来向服务器发送请求，并对服务器返回结果进行展示:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>index</title><script type="text/javascript"src="${pageContext.request.contextPath}/jquery-3.6.0.js"></script><script language="JavaScript">function getInfo() {$.get("http://localhost:8080/chapter12/getInfo.jsp?nocache="+new  Date().getTime(),function (data) {$("#showInfo").html(data);});}$(document).ready(function () {getInfo();//调用getInfo()方法获取公告信息window.setInterval("getInfo()",600000);})</script>
</head>
<body>
<section><marquee id="showInfo" direction="up" scrollamount="3"></marquee>
</section>
</body>
</html>

创建getInfo.jsp文件用于执行SQL语句并对查询结果进行输出:

<%@ page language="java" contentType="text/html;charset=UTF-8"pageEncoding="UTF-8" %>
<%@page import="java.sql.*" %>
<jsp:useBean id="conn" class="cn.itcast.dao.ConnDB"scope="page"></jsp:useBean>
<ul><%ResultSet rs=conn.executeQuery("select title from info order by id desc");if(rs.next()){do{out.print("<li>"+rs.getString(1)+"</li>");}while (rs.next());}else{out.print("<li>暂无公告信息！</li>");}%>
</ul>

创建创建数据库请问文件ConnDB.java工具类：

package cn.itcast.dao;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
public class ConnDB {public Connection conn =null;public Statement stmt = null;public ResultSet rs = null;private static String propFileName= "connDB.properties";private static Properties prop=new Properties();private static String dbClassName ="";private static String dbUrl="";private static String user="";private static String pass="";static{try{//将Properties文件读取到InputStream对象中InputStream in=ConnDB.class.getResourceAsStream(propFileName);prop.load(in);dbClassName = prop.getProperty("DB_CLASS_NAME");dbUrl = prop.getProperty("DB_URL");user = prop.getProperty("user");pass = prop.getProperty("pass");}catch (Exception e){e.printStackTrace();                             //输出异常信息}}/*** 连接数据库*/public  Connection getConection(){try{Class.forName(dbClassName).newInstance();conn = DriverManager.getConnection(dbUrl,user,pass);}catch (Exception ee){ee.printStackTrace();}if(conn==null){System.err.print("连接失败");}return conn;}/*** 执行查询*/public ResultSet executeQuery(String sql){try{conn=getConection();stmt =conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);rs =stmt.executeQuery(sql);}catch (SQLException ex){System.err.print(ex.getErrorCode());}return rs;}public void close(){try{if(rs!=null){rs.close();}if (stmt!=null){stmt.close();}if (conn!=null){conn.close();}}catch (Exception e){e.printStackTrace();}}
}