我正在用 Java、JavaFX 和 MySQL 做一个小组项目，我在尝试用 JDBC 连接到我的数据库时遇到了一个大问题。我有系统地通过 DriverManager.getConnection() 方法抛出这个错误：
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.
编辑：这是整个堆栈跟踪：
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:175)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:446)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:239)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:188)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:681)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:252)
at controller.Controller.dbconnect(Controller.java:34)
at controller.Controller.<init>(Controller.java:18)
at App.start(App.java:15)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(GtkApplication.java:290)
at java.base/java.lang.Thread.run(Thread.java:833)
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:62)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:150)
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:166)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:89)
at com.mysql.cj.NativeSession.connect(NativeSession.java:121)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:945)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:815)
... 17 more
Caused by: java.net.ConnectException: Connection refused
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:153)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63)
... 20 more
抛出错误的代码是：
public Connection dbconnect() {
Connection conn = null;
try {
conn = DriverManager
.getConnection(
"jdbc:mysql://127.0.0.1:3306/cookbook?user=root&password=ABC&useSSL=false");
} catch (SQLException e) {
System.out.println(e.getMessage());
}
return conn;
}
我在 Windows 10 中使用 VSCode 和 Debian WSL 进行编译。我安装了 MySQL Server、Workbench 和 Connector/J 版本 8.0.33.
我已经花了几个小时试图解决这个问题。它非常适合组中的其他成员，我可以连接到在线数据库（使用this），所以我可以确定问题出在我的机器上。我在网上找到了很多不同的可能原因和解决方案，太多了，我无法一一列举，但这里有一些：
my.ini没有任何效果，我的选择和想法都用完了，所以也许你可以有一个我从未尝试过的新解决方案。