JDBC的简单使用

本文仅用作云笔记作用，不像博客那样严密

完成

最后的代码如下：

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

public class Hello {

    public static final String URL = "jdbc:mysql://localhost:3306/guestbook?useSSL=false";
    public static final String USER = "root";
    public static final String PASSWORD = "";

    public static void main(String[] args) throws Exception {
        //1.加载驱动程序
        Class.forName("com.mysql.jdbc.Driver");
        //2. 获得数据库连接
        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        //3.操作数据库，实现增删改查
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery("SELECT * FROM message");
        //如果有数据，rs.next()返回true
        while(rs.next()){
            System.out.println("姓名：" + rs.getString("username")+" 消息："+rs.getString("info"));
        }
    }
}

数据库里的内容：

遇到的坑

1. Exception in thread “main” java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
   没有导入数据库驱动jar包，从菜鸟教程下载jar包，然后添加进项目中就可以了

2. WARN: Establishing SSL connection without server’s identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn’t set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to ‘false’. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.

只需要在url后面添加上?useSSL=false，举例public static final String URL = "jdbc:mysql://localhost:3306/guestbook?useSSL=false";