在纯JPA设置中获取数据库连接

Session EntityManager . 使用JPA 1.0,您必须执行以下操作:

Session session = (Session)em.getDelegate();
Connection conn = session.connection();

请注意 getDelegate() 是不可移植的,这个方法的结果是特定于实现的:上面的代码在JBoss中工作,对于GlassFish,您必须对其进行调整—看一下 Be careful while using EntityManager.getDelegate() .

Connection conn = em.unwrap(Session.class).connection();

如果在容器内运行,还可以对配置的 DataSource .

根据 hibernate 文件 here ,

. (计划在4.x中删除)。根据需要更换;直接使用JDBC 嫁妆(org.hibernate.jdbc.Work) ...

Session session = entityManager.unwrap(Session.class);
session.doWork(new Work() {

    @Override
    public void execute(Connection connection) throws SQLException {
        // do whatever you need to do with the connection
    }
});

如果您使用的是JAVA EE 5.0,那么最好的方法是使用@Resource注释将数据源注入类(例如EJB)的属性中,以保存遗留报告工具的数据源资源(例如Oracle数据源),方法如下:

@Resource(mappedName="jdbc:/OracleDefaultDS") DataSource datasource;

稍后,您可以通过以下方式获取连接,并将其传递给遗留报告工具:

Connection conn = dataSource.getConnection();

如果使用EclipseLink:

entityManager.getTransaction().begin();
java.sql.Connection connection = entityManager.unwrap(java.sql.Connection.class);
...
entityManager.getTransaction().commit();

:

Session session = entityManager.unwrap(Session.class);
session.doWork(connection -> doSomeStuffWith(connection));

由于@Pascal建议的代码已被@Jacob否决,我发现 this another way

import org.hibernate.classic.Session;
import org.hibernate.connection.ConnectionProvider;
import org.hibernate.engine.SessionFactoryImplementor;

Session session = (Session) em.getDelegate();
SessionFactoryImplementor sfi = (SessionFactoryImplementor) session.getSessionFactory();
ConnectionProvider cp = sfi.getConnectionProvider();
Connection connection = cp.getConnection();

这个词 冬眠 .

日蚀

• Getting a JDBC Connection from an EntityManager

• EntityManager 必须连接到 Transaction 或者 unwrap null
• 我不确定关闭连接的责任。

// --------------------------------------------------------- EclipseLink
try {
    final Connection connection = manager.unwrap(Connection.class);
    if (connection != null) { // manage is not in any transaction
        return function.apply(connection);
    }
} catch (final PersistenceException pe) {
    logger.log(FINE, pe, () -> "failed to unwrap as a connection");
}

冬眠

// using vendor specific APIs
final Session session = (Session) manager.unwrap(Session.class);
//return session.doReturningWork<R>(function::apply);
return session.doReturningWork(new ReturningWork<R>() {
    @Override public R execute(final Connection connection) {
        return function.apply(connection);
    }
});

嗯,我们(至少我)可能不需要任何特定于供应商的依赖关系。 Proxy

try {
    // See? You shouldn't fire me, ass hole!!!
    final Class<?> sessionClass
            = Class.forName("org.hibernate.Session");
    final Object session = manager.unwrap(sessionClass);
    final Class<?> returningWorkClass
            = Class.forName("org.hibernate.jdbc.ReturningWork");
    final Method executeMethod
            = returningWorkClass.getMethod("execute", Connection.class);
    final Object workProxy = Proxy.newProxyInstance(
            lookup().lookupClass().getClassLoader(),
            new Class[]{returningWorkClass},
            (proxy, method, args) -> {
                if (method.equals(executeMethod)) {
                    final Connection connection = (Connection) args[0];
                    return function.apply(connection);
                }
                return null;
            });
    final Method doReturningWorkMethod = sessionClass.getMethod(
            "doReturningWork", returningWorkClass);
    return (R) doReturningWorkMethod.invoke(session, workProxy);
} catch (final ReflectiveOperationException roe) {
    logger.log(Level.FINE, roe, () -> "failed to work with hibernate");
}

OpenJPA公司

• Runtime Access to DataSource
• OPENJPA-1803 Unwrap EntityManager to Connection

我不确定OpenJPA是否已经提供了一种使用 unwrap(Connection.class)

不清楚关闭连接的责任。文件(上面的链接之一)似乎说得很清楚,但我不擅长英语。

try {
    final Class<?> k = Class.forName(
            "org.apache.openjpa.persistence.OpenJPAEntityManager");
    if (k.isInstance(manager)) {
        final Method m = k.getMethod("getConnection");
        try {
            try (Connection c = (Connection) m.invoke(manager)) {
                return function.apply(c);
            }
        } catch (final SQLException sqle) {
            logger.log(FINE, sqle, () -> "failed to work with openjpa");
        }
    }
} catch (final ReflectiveOperationException roe) {
    logger.log(Level.FINE, roe, () -> "failed to work with openjpa");
}

Hibernate在内部使用ConnectionProvider来获取连接。从hibernate javadoc:

ConnectionProvider接口不打算向应用程序公开。相反,Hibernate在内部使用它来获取连接。

我今天遇到了这个问题,这就是我的窍门,对我很有效:

   EntityManagerFactory emf = Persistence.createEntityManagerFactory("DAOMANAGER");
   EntityManagerem = emf.createEntityManager();

   org.hibernate.Session session = ((EntityManagerImpl) em).getSession();
   java.sql.Connection connectionObj = session.connection();

虽然不是最好的方法,但它确实起到了作用。

import java.sql.Connection;
import org.apache.openjpa.persistence.OpenJPAEntityManager;
import org.apache.openjpa.persistence.OpenJPAPersistence;

public final class MsSqlDaoFactory {


       public static final Connection getConnection(final EntityManager entityManager) {
              OpenJPAEntityManager openJPAEntityManager = OpenJPAPersistence.cast(entityManager);
              Connection connection = (Connection) openJPAEntityManager.getConnection();
              return connection;

        }

}

我使用的是Hibernate的旧版本(3.3.0)和OpenEJB的最新版本(4.6.0)。我的解决方案是:

EntityManagerImpl entityManager = (EntityManagerImpl)em.getDelegate();
Session session = entityManager.getSession();
Connection connection = session.connection();
Statement statement = null;
try {
    statement = connection.createStatement();
    statement.execute(sql);
    connection.commit();
} catch (SQLException e) {
    throw new RuntimeException(e);
}

Commit can not be set while enrolled in a transaction

因为上面的代码在EJB控制器中(您不能 commit 在交易中)。我用 @TransactionAttribute(value = TransactionAttributeType.NOT_SUPPORTED) 问题消失了。

Connection getConnection() {
    Session session = entityManager.unwrap(Session.class);
    MyWork myWork = new MyWork();
    session.doWork(myWork);
    return myWork.getConnection();
}

private static class MyWork implements Work {

    Connection conn;

    @Override
    public void execute(Connection arg0) throws SQLException {
        this.conn = arg0;
    }

    Connection getConnection() {
        return conn;
    }

}