java如何修复错误“上次成功发送到服务器的数据包是0毫秒前的。驱动程序尚未从服务器接收到任何数据包”

Question

您好，我刚刚创建了我的应用程序，它仍然是空的，我只是放置了一个类，允许连接到我的sql数据库，但当我运行我的应用程序时，我得到以下错误：

AVERTISSEMENT: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@17460bca -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 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:832) at com.mysql.cj.jdbc.ConnectionImpl.(ConnectionImpl.java:456) at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240) at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207) at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:175) at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:220) at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:206) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:203) at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1138) at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1125) at com.mchange.v2.resourcepool.BasicResourcePool.access$700(BasicResourcePool.java:44) at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1870) at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696) 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 sun.reflect.GeneratedConstructorAccessor34.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) 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:152) at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:952) at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:822) ... 12 more Caused by: java.net.ConnectException: Connection refused: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) at java.net.Socket.connect(Socket.java:589) at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:173) at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65) ... 15 more

以下是我编写的代码：

package com.luv2code.testdb;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
/**
 * Servlet implementation class TestDbServlet
 */
@WebServlet("/TestDbServlet")
public class TestDbServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // établir la connexion à mysql :

        String user="springstudent";
        String password="springstudent";
        String jdbcUrl="jdbc:mysql://localhost:3309/web_customer_tracker?useSSL=false&serverTimezone=UTC";
        String driver="com.mysql.jdbc.Driver";

        try {

            PrintWriter out= response.getWriter();
            out.println("Connection à  la base de donnée :"+jdbcUrl);

            Class.forName(driver);
            Connection cnx;
            cnx=DriverManager.getConnection(jdbcUrl, user, password);

            out.println("Success !!!!!!!!!");

            cnx.close();
        }

        catch(Exception ex) {
            ex.printStackTrace();
            throw new ServletException(ex);
        }
    }

}

我将端口3309改为3306，因为端口3306在我的mysqlworkbench中不工作，它给了我以下错误：

即使我想用端口3306创建一个新数据库，也会出现以下错误：

我不知道是不是这个端口问题导致了这个错误

请帮帮我