jdbc，采用properties文件保存数据库账号密码以及链接

1,在根目录创建 mysql.properties 文件,使用这个文件是为了方便以后生成class文件后可修改链接任意数据库

 

2,导入jar包，自行百度下载。

 

3,写一个 SqlUtil.class （Sql工具类）

package com.sogood.util;
import java.io.IOException;
import java.sql.*;
import java.util.Properties;

public class SqlUtil {
    private static String username;
    private static String password;
    private static String url;

    static {
        Properties pps = new Properties();
        try {
            pps.load(SqlUtil.class.getResourceAsStream("/com/sogood/mysql.properties"));
            username = pps.getProperty("username");
            password = pps.getProperty("password");
            url = pps.getProperty("url");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() {
        Connection con = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection(url, username, password);// 创建数据连接
        } catch (SQLException e) {
            e.printStackTrace();
            System.out.println("数据库连接失败");
        } catch (ClassNotFoundException e) {
            throw new RuntimeException("驱动类找不到");
        }
        return con;
    }

    public static void close(Connection con, Statement stm, ResultSet rs) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (stm != null) {
            try {
                stm.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (con != null) {
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

　

4，写一个Demo.class 类测试一下

package com.sogood.jdbc;

import com.sogood.util.SqlUtil;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class Demo {
    public static void main(String[] args) throws SQLException {
        query();
    }

    private static void query() {
        Connection con = null;
        Statement stm = null;
        ResultSet rs = null;
        try {
            con = SqlUtil.getConnection();
            String sql = "SELECT * FROM STUDENT";
            stm = con.createStatement();
            rs = stm.executeQuery(sql);
            System.out.println("查询结果:");
            while (rs.next()) {
                int id = rs.getInt("id");
                System.out.println("id = " + id);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            SqlUtil.close(con, stm, rs);
        }
    }
}