java - 使用 Hibernate 和 JDBC 关闭连接

Question

我有以下问题。我正在编写一个带有服务器数据库的桌面java应用程序。我也用 hibernate 。当我运行应用程序时，一切正常，并且与数据库的连接正确，但几分钟后，当我对数据库执行一些操作时，出现以下错误:

Exception thrown: 
Class: model.MainRepository

    Stack Trace:
    org.hibernate.TransactionException: JDBC begin transaction failed: 
        at org.hibernate.resource.jdbc.internal.AbstractLogicalConnectionImplementor.begin(AbstractLogicalConnectionImplementor.java:72)
        at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.begin(LogicalConnectionManagedImpl.java:238)
        at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.begin(JdbcResourceLocalTransactionCoordinatorImpl.java:213)
        at org.hibernate.engine.transaction.internal.TransactionImpl.begin(TransactionImpl.java:52)
        at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1443)
        at model.MainRepository.addTrainingToUser(MainRepository.java:151)
        at model.Parser.parseFilesWatch(Parser.java:85)
        at controller.UploadDataController$1.call(UploadDataController.java:148)
        at javafx.concurrent.Task$TaskCallable.call(Task.java:1423)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.lang.Thread.run(Thread.java:745)
    Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

    Last packet sent to the server was 11 ms ago.
        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:422)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2985)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2871)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3414)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
        at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536)
        at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4874)
        at org.hibernate.resource.jdbc.internal.AbstractLogicalConnectionImplementor.begin(AbstractLogicalConnectionImplementor.java:67)
        ... 10 more
    Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2431)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2882)
        ... 17 more

    Exception thrown: 
    Class: model.MainRepository
    Stack Trace:
    org.hibernate.TransactionException: JDBC begin transaction failed: 
        at org.hibernate.resource.jdbc.internal.AbstractLogicalConnectionImplementor.begin(AbstractLogicalConnectionImplementor.java:72)
        at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.begin(LogicalConnectionManagedImpl.java:238)
        at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.begin(JdbcResourceLocalTransactionCoordinatorImpl.java:213)
        at org.hibernate.engine.transaction.internal.TransactionImpl.begin(TransactionImpl.java:52)
        at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1443)
        at model.MainRepository.sendTrainingDetails(MainRepository.java:184)
        at model.Parser.parseFilesWatch(Parser.java:94)
        at controller.UploadDataController$1.call(UploadDataController.java:148)
        at javafx.concurrent.Task$TaskCallable.call(Task.java:1423)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.lang.Thread.run(Thread.java:745)
    Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Connection.close() has already been called. Invalid operation in this state.
        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:422)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.Util.getInstance(Util.java:381)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
        at com.mysql.jdbc.ConnectionImpl.getMutex(ConnectionImpl.java:3018)
        at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4827)
        at org.hibernate.resource.jdbc.internal.AbstractLogicalConnectionImplementor.begin(AbstractLogicalConnectionImplementor.java:67)
        ... 10 more

这是我的 hibernate.cfg.xml 文件:

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.pool_size">1</property>
        <property name="hibernate.connection.url">jdbc:mysql://sql.aaa.nazwa.pl:1111/aaaa</property>
        <property name="hibernate.connection.username">aaa</property>
        <property name="hibernate.connection.password">bbb</property>
        <property name="show_sql">true</property>
        <mapping resource="model/models.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

HibernateUtil.java

package model;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

/**
 * Created by Piotr on 2015-10-11.
 */
public class HibernateUtil {

    private static final SessionFactory sessionFactory = buildSessionFactory();

    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            return new Configuration().configure().buildSessionFactory();

        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public static void shutdown() {
        // Close caches and connection pools
        getSessionFactory().close();
    }
}

以及对数据库的示例操作:

public void addUser(User user) {
        Session session = HibernateUtil.getSessionFactory().openSession();
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
            session.save(user);
            tx.commit();
        } catch (Exception e) {
            if (tx != null) tx.rollback();
            Logger.saveToLogFile(e, this.getClass().getName());
        } finally {
            session.close();
        }
    }

Answer 1

好的，我已经解决了这个问题。应设置 c3p0 中名为“idleConnectionTestPeriod”的参数。来自文档“如果这是一个大于 0 的数字，c3p0 将每隔此秒数测试所有空闲、池化但未 checkout 的连接。”