JavaIDEA连接MySQL教程及常见错误解决

客官°小女子只卖身不卖艺 2021-11-16 16:40 625阅读 0赞

## （一）复制jar包 ##

将对应MySQL版本的jar包，复制libs目录中（libs是自己创建的）  
![在这里插入图片描述][20190729085951608.png]

## （二）添加library ##

复制成功后，右击libs,选择Add to Library…

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NoYXh1MTIz_size_16_color_FFFFFF_t_70]

## (三）注册驱动 ##

Class.forName("com.mysql.jdbc.Driver");

注意，此处可能会出现问题：

> Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is`com.mysql.cj.jdbc.Driver’. The driver is  
> automatically registered via the SPI and manual loading of the driver  
> class is generally unnecessary.

将代码改成这样既可：

Class.forName("com.mysql.cj.jdbc.Driver");

## （四）获取数据库的连接对象 ##

Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/db1", "root", "root");

此处可能会出现错误：  
**错误一：**

> \*\* BEGIN NESTED EXCEPTION \*\* javax.net.ssl.SSLException MESSAGE: closing inbound before receiving peer’s close\_notify STACKTRACE:  
> javax.net.ssl.SSLException: closing inbound before receiving peer’s  
> close\_notify  
> at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:129)  
> at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:117)  
> at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:308)  
> at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:264)  
> at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:255)  
> at java.base/sun.security.ssl.SSLSocketImpl.shutdownInput(SSLSocketImpl.java:645)  
> at java.base/sun.security.ssl.SSLSocketImpl.shutdownInput(SSLSocketImpl.java:624)  
> at com.mysql.cj.protocol.a.NativeProtocol.quit(NativeProtocol.java:1312)  
> at com.mysql.cj.NativeSession.quit(NativeSession.java:182)  
> at com.mysql.cj.jdbc.ConnectionImpl.realClose(ConnectionImpl.java:1750)  
> at com.mysql.cj.jdbc.ConnectionImpl.close(ConnectionImpl.java:720)  
> at org.mybatis.generator.config.Context.closeConnection(Context.java:535)  
> at org.mybatis.generator.config.Context.introspectTables(Context.java:468)  
> at org.mybatis.generator.api.MyBatisGenerator.generate(MyBatisGenerator.java:222)  
> at org.mybatis.generator.api.ShellRunner.main(ShellRunner.java:117)
> 
> \*\* END NESTED EXCEPTION \*\*

**解决方法：**

原因应该是MySQL的版本太高导致的。  
设置useSSL为false既可

**错误二：**

> The server time zone value ‘ÖÐ¹ú±ê×¼Ê±¼ä’ is unrecognized or  
> represents more than one time zone.

原因是MySQL的时区不统一

键盘上这个键  
![在这里插入图片描述][20190729091219245.png]

*  R 输入cmd

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NoYXh1MTIz_size_16_color_FFFFFF_t_70 1]  
进入命令行

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NoYXh1MTIz_size_16_color_FFFFFF_t_70 2]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NoYXh1MTIz_size_16_color_FFFFFF_t_70 3]

输入

show variables like '%time_zone%';

查看时区，如果是System, 则进行修改

set global time_zone='+8:00';

就该为正确的既可。

当然还有另外一种方法：

修改代码中的URL:

Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/db1" +
                    "?serverTimezone=GMT%2B8&useSSL=false", "root", "root");

## （五）定义sql语句 ##

String sql = "update students set age =10 where id ='1'";

## （六）获取sql 的对象 ##

Statement stmt = connection.createStatement();

## （七）执行sql语句 ##

int count = stmt.executeUpdate(sql);

## （八）打印结果 ##

System.out.println(count);

## （九）释放资源 ##

stmt.close();
    connection.close();

完整代码：

import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.Statement;
    
    public class demo01_jdbc {
    
        public static void main(String[] args) throws Exception{
            //1. 复制jar包到libs 目录下右击libs 点击add as lib...
            //2. 注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //3. 获取数据库的连接对象
            Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/db1" +
                    "?serverTimezone=GMT%2B8&useSSL=false", "root", "root");
            //4. 定义sql语句
            String sql = "update students set age =10 where id ='1'";//?serverTimezone=GMT%2B8
            //5.获取sql 的对象
            Statement stmt = connection.createStatement();
            //6.执行sql语句
            int count = stmt.executeUpdate(sql);
            //7.打印结果
            System.out.println(count);
            //8.释放资源
            stmt.close();
            connection.close();
        }
    }

[20190729085951608.png]: /images/20211116/ec470c529d3947559f7d04aa85ec78d8.png
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[20190729091219245.png]: /images/20211116/fa06c38e5a394a469c308339723acf62.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NoYXh1MTIz_size_16_color_FFFFFF_t_70 1]: /images/20211116/c00fad359260467198ccebc8c777fb08.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NoYXh1MTIz_size_16_color_FFFFFF_t_70 3]: /images/20211116/a655fef1f0ea48f6ad3c11dec218089c.png