import java.sql.*;
public class Gradation { //创建类
//连接数据库方法
public Connection getConnection() throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3360/test", "root", "root8888");
return connection; //返回Connection对象
}
public static void main(String[] args) { //主方法
Gradation gradation = new Gradation(); //创建本类对象
Connection connection = null; //声明connection对象
Statement statement = null; //声 明Statement对象
ResultSet result = null; //声明ResultSet对象
try {
connection = gradation.getConnection(); //与数据库建立连接
statement = (Statement) connection.createStatement(); //实例话Statement对象
result = statement.executeQuery("select * from tb_stu"); //执行SQL语句,返回结果集
while (result.next()) { //如果当前语句不是最后一条则进入循环
String idString = result.getString("id");
String nameString = result.getString("name");
String sexString = result.getString("sex");
//获取列名是birthday的字段值
String birthdayString = result.getString("birthday");
System.out.println("编号:" + idString);
System.out.println("姓名:" + nameString);
System.out.println("性别:" + sexString);
System.out.println("生日:" + birthdayString);
}
} catch (Exception e) {
e.printStackTrace();
} finally { //依次关闭数据库资源
if (result != null) {
try {
result.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (statement != null) {
try {
((Connection) statement).close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
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 mysql.connector.java@8.0.24/com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
at mysql.connector.java@8.0.24/com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at mysql.connector.java@8.0.24/com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:833)
at mysql.connector.java@8.0.24/com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:453)
at mysql.connector.java@8.0.24/com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
at mysql.connector.java@8.0.24/com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:677)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:228)
at Gradation.getConnection(Gradation.java:7)
at Gradation.main(Gradation.java:17)
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:78)
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 mysql.connector.java@8.0.24/com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
at mysql.connector.java@8.0.24/com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
at mysql.connector.java@8.0.24/com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
at mysql.connector.java@8.0.24/com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
at mysql.connector.java@8.0.24/com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:89)
at mysql.connector.java@8.0.24/com.mysql.cj.NativeSession.connect(NativeSession.java:144)
at mysql.connector.java@8.0.24/com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:953)
at mysql.connector.java@8.0.24/com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:823)
... 7 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:576)
at java.base/sun.nio.ch.Net.connect(Net.java:565)
at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)
at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:333)
at java.base/java.net.Socket.connect(Socket.java:645)
at mysql.connector.java@8.0.24/com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155)
at mysql.connector.java@8.0.24/com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63)
... 10 more