我有一个MySQL数据库。我的朋友正试图使用我的公共IP从另一台计算机访问它。
这是他用来测试连接的程序:
public class Main {
public static void main(String args[]) {
String url = "jdbc:mysql://IPadresss:3307/javabase";
String username = "bob";
String password = "bob";
Properties properties = new Properties();
properties.setProperty("bob", "bob");
properties.setProperty("bob", "bob");
properties.setProperty("useSSL", "false");
properties.setProperty("autoReconnect", "true");
System.out.println("Connecting database...");
try (Connection connection = DriverManager.getConnection(url, properties)) {
System.out.println("Database connected!");
} catch (SQLException e) {
throw new IllegalStateException("Cannot connect the database!", e);
}
}
}
这是我的客户朋友得到的错误:
Connecting database...
Exception in thread "main" java.lang.IllegalStateException: Cannot connect the database!
at SQLConnector.Main.main(Main.java:23)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.Util.getInstance(Util.java:408)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:918)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:897)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:886)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2163)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2088)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:806)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:410)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:328)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:208)
at SQLConnector.Main.main(Main.java:20)
Caused by: java.sql.SQLException: Access denied for user ''@'Freinds ip' (using password: NO)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:964)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3970)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3906)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:873)
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1710)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1226)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2253)
at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2104)
... 13 more
请帮我找出我连接服务器的方法有什么问题,我已经远程授予了我的朋友(用户"bob")权限。
因此,您会出现以下错误:
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:通信链接失败java.net.ConnectException:连接拒绝
这可能有多种原因,我引用的答案
如果获得
SQLException: Connection refused
或Connection timed out
或MySQL特定的CommunicationsException
:通信链接如果失败,则意味着数据库根本无法访问。这可能有以下一个或多个原因:
- JDBC URL中的IP地址或主机名错误
- 本地DNS服务器无法识别JDBC URL中的主机名
- JDBC URL中缺少端口号或端口号错误。[假设你提到的是正确的]
- 数据库服务器已关闭
- DB服务器不接受TCP/IP连接
- 数据库服务器的连接已用完
- Java和DB之间的某些东西正在阻塞连接,例如防火墙或代理
要解决其中一个问题,请遵循以下建议:
- 使用ping验证并测试它们
- 请刷新DNS或在JDBC URL中使用IP地址
- 基于MySQL数据库的my.cnf进行验证
- 启动数据库
- 验证mysqld是否在没有--skip网络选项的情况下启动
- 重新启动数据库并相应地修复代码,使其最终关闭连接
- 禁用防火墙和/或配置
- 防火墙/代理以允许/转发端口