为什么java获取mysql数据库失败
MySQL是8.0版本
已经打开防火墙端口权限了,还有root权限为%了
运行后报错的文本:
com.mysql.jdbc.exceptions.jdbc4.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 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.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:989)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:341)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2192)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2225)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2024)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:779)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
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.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:681)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:229)
at net.jdbc.main(jdbc.java:12)
Caused by: java.net.UnknownHostException: 不知道这样的主机。 (locallhost)
at java.base/java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.base/java.net.InetAddress$PlatformNameService.lookupAllHostAddr(InetAddress.java:933)
at java.base/java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1519)
at java.base/java.net.InetAddress$NameServiceAddresses.get(InetAddress.java:852)
at java.base/java.net.InetAddress.getAllByName0(InetAddress.java:1509)
at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1367)
at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1301)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:188)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:300)
... 16 more
```java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class jdbc {
public static void main(String[] args) {
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/gxgl", "root", "123456");
System.out.print("数据库连接成功");
} catch (Exception e) {
e.printStackTrace();
}
finally {
if(null!=conn) {
try {
conn.close();
System.out.print("关闭数据库连接");
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
是用这个代码运行的