【发布时间】：2018-12-07 17:01:25
【问题描述】：
首先我想说声抱歉，因为这个问题被问了十亿次，但我仍然不确定我的错误是什么。
所以我遇到的问题如下：
我尝试使用主机、端口等连接到我的 MySQL 服务器，但出现“连接被拒绝”异常。这通常意味着问题与连接/登录有关，并且意味着它无法连接到 MySQL 服务器。
当我通过 phpMyAdmin 登录该服务器时，我使用的是完全相同的数据。下面是错误和我的源代码，希望大家能告诉我我的错误是什么。
提前致谢。
例外：
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:172)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:862)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:444)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:230)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:226)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at teabot.database.DatabaseConnection.<init>(DatabaseConnection.java:26)
at teabot.database.DatabaseHelper.setupDB(DatabaseHelper.java:16)
at teabot.main.Main.init(Main.java:39)
at teabot.main.Main.main(Main.java:69)
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.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:59)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:103)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:149)
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:165)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:92)
at com.mysql.cj.NativeSession.connect(NativeSession.java:152)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:982)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:852)
... 9 more
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:173)
at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:66)
源代码：
protected DatabaseConnection(String host, int port, String databaseName, String username, String password) {
boolean error = false;
try {
String url = "jdbc:mysql://" + host + ":" + port + "/" + databaseName;
this.connection = DriverManager.getConnection(url, username, password);
} catch (SQLException e) {
e.printStackTrace();
Helper.log(2, e.getMessage());
error = true;
}
if (!error) {
Helper.log(0, "Database is ready.");
}
}
编辑： 我的问题是我的 MySQL 服务器没有监听该端口，因为当我使用 phpMyAdmin 尝试它时，我忘记了它在同一台机器上运行。
【问题讨论】：
-
如果您可以使用 PHPMyAdmin 连接，但不能使用 JDBC，那么这可能表明 PHPMyAdmin 正在使用 UNIX 域套接字进行连接，并且 TCP/IP（网络）已禁用或正在使用一个不同的端口。查看链接的副本。