使用IDEA学习JSP代码第028课-CFANZ编程社区

new397.properties

jdbc.driver_class = com.mysql.jdbc.Driver
jdbc.connection.url = jdbc:mysql://localhost:3306/test
jdbc.connection.username = root
jdbc.connection.password = mysql123

new398.java

package pack03;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class new398_ConfigManager
{
    private static new398_ConfigManager configManager;

    private static Properties properties;

    public new398_ConfigManager()
    {
        String configFile = "new397.properties";
        //使用idea，在web目录下新建一个文件夹，然后标记为resources，将properties文件放入其中。
        properties = new Properties();
        InputStream in = new398_ConfigManager.class.getClassLoader().getResourceAsStream(configFile);
        try
        {
            properties.load(in);
            in.close();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }

    }

    public static new398_ConfigManager getInstance()
    {
        if(configManager == null)
        {
            configManager = new new398_ConfigManager();
        }

        return configManager;
    }

    public String getString(String key)
    {
        return properties.getProperty(key);
    }
}

new399.jsp

<%@ page import="java.sql.*" %>
<%@ page import="pack03.new398_ConfigManager" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title></title>
    <link rel="stylesheet" href="../other/boot/css/bootstrap.min.css">
    <script type="text/javascript" src="../other/jQuery/jQuery-3.4.1.js"></script>
    <script type="text/javascript" src="../other/boot/js/bootstrap.min.js"></script>



</head>
<body>
    <%!

        public void getNewsList()
        {
            Connection conn = null;
            Statement stmt = null;
            ResultSet rs  = null;

            String driver = new398_ConfigManager.getInstance().getString("jdbc.driver_class");
            String url = new398_ConfigManager.getInstance().getString("jdbc.connection.url");
            String username = new398_ConfigManager.getInstance().getString("jdbc.connection.username");
            String password = new398_ConfigManager.getInstance().getString("jdbc.connection.password");

            try
            {
                Class.forName(driver);
                conn = DriverManager.getConnection(url,username,password);
                stmt = conn.createStatement();
                rs = stmt.executeQuery("select a,b,c from table1"); //运行后，提示错误，表不存在
                while (rs.next())
                {
                    int id = rs.getInt("a");
                    String title = rs.getString("b");
                    String summary = rs.getString("c");
                    String content = rs.getString("content");
                    String author = rs.getString("author");
                    Timestamp time = rs.getTimestamp("createdate");
                    System.out.println(id + "\t" + title + "\t" + summary + "\t" + content + "\t" + author + "\t" + time);
                    //以上均为模拟代码，供参考
                }

            }
            catch (SQLException | ClassNotFoundException e)
            {
                e.printStackTrace();
            }
            finally
            {
                try
                {
                    if(rs != null)
                    {
                        rs.close();
                    }

                    if(stmt != null)
                    {
                        stmt.close();
                    }

                    if(conn != null)
                    {
                        conn.close();
                    }
                }
                catch (SQLException e)
                {
                    e.printStackTrace();
                }
            }


        }
    %>

    <%
        getNewsList(); //表没有建立，提示错误
    %>
</body>
</html>