记录成功去除bug的瞬间

注册驱动成功!
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836)
    at com.mysql.cj.jdbc.ConnectionImpl.(ConnectionImpl.java:456)
    at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
    at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197)
    at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:681)
    at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:229)
    at SelectTest.main(SelectTest.java:22)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
    at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91)
    at com.mysql.cj.NativeSession.connect(NativeSession.java:144)
    at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:956)
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:826)
    ... 6 more
Caused by: java.net.ConnectException: Connection refused: connect
    at java.base/sun.nio.ch.Net.connect0(Native Method)
    at java.base/sun.nio.ch.Net.connect(Net.java:579)
    at java.base/sun.nio.ch.Net.connect(Net.java:568)
    at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)
    at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:327)
    at java.base/java.net.Socket.connect(Socket.java:633)
    at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155)
    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65)
    ... 9 more

百度了许久，一个晚上+今天下午的一个小时左右，看到了某位同学的文章，得到启示，稍加改动，bug破解。开心！

import java.sql.*;

public class SelectTest {
    public static void main(String[] args){
    	
    	//构建Java和数据库之间的桥梁介质
        try{            
            Class.forName("com.mysql.cj.jdbc.Driver");
            System.out.println("注册驱动成功!");
        }catch(ClassNotFoundException e1){
            System.out.println("注册驱动失败!");
            e1.printStackTrace();
            return;
        }
      
     String url="jdbc:mysql://localhost:3396/test?serverTimezone=GMT&useSSL=true";    //大概错误是从这里开始的，连接失败
     
        Connection conn = null;
        try {
        	//构建Java和数据库之间的桥梁：URL，用户名，密码
            conn = DriverManager.getConnection(url, "root", "2001");
            
            //构建数据库执行者
            Statement stmt = conn.createStatement(); 
            System.out.println("创建Statement成功！");      
            
            //执行SQL语句并返回结果到ResultSet
            ResultSet rs = stmt.executeQuery("select bookid, bookname, price from e_book order by bookid");
                        
            //开始遍历ResultSet数据
            while(rs.next())
            {
            	System.out.println(rs.getInt(1) + "," + rs.getString(2) + "," + rs.getInt("price"));
            }
            
            rs.close();
            stmt.close();
            
        } catch (SQLException e){
            e.printStackTrace();
        }
        finally
        {
        	try
        	{
        		if(null != conn)
        		{
            		conn.close();
            	}
        	}
        	catch (SQLException e){
                e.printStackTrace();
        	}        	
        }
    }
}

 String url="jdbc:mysql://localhost/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false"; 

修改之后就成功了。

直接cv一个认为不错的文章的地址

useSSL=false&useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true 等一些Mysql JDBC Url参数说明_hcmony的博客-CSDN博客