Hibernate postgresql通知功能

Question

我正在编写一个使用hibernate + JPA作为ORM和postgresql 9.3作为数据库后端的应用程序，我需要对某些数据库事件做出反应。
更确切地说，我想在将新行插入表中时构建一个使用pg_notify（）的触发器。
我已经读过这个，但所有的教程都是直接的jdbc连接，而不是通过hibernate。
我（认为我）不能使用hibernate事件，因为行不是通过hibernate插入的，而是通过第三方应用程序插入的。

有什么方法可以通过hibernate接收通过pg_notify发送的通知吗？

- 更新
现在我有一个classCastException：

java.lang.ClassCastException: com.sun.gjc.spi.jdbc40.ConnectionWrapper40 cannot be cast to org.postgresql.PGConnection
    at com.xxx.core.impl.dao.PostgresqlLowLevelNotificationDAOImpl$1.execute(PostgresqlLowLevelNotificationDAOImpl.java:36)
    at com.xxx.core.impl.dao.PostgresqlLowLevelNotificationDAOImpl$1.execute(PostgresqlLowLevelNotificationDAOImpl.java:1)

我必须提到我使用Glassfish 4.0作为AS。 连接池在glassfish上创建，并通过jndi由app访问。 此外，EntityManager由容器注入Spring。 这是我的代码：

@Named
public class PostgresqlLowLevelNotificationDAOImpl implements PostgresqlLowLevelNotificationDAO{

    @PersistenceContext(type =PersistenceContextType.TRANSACTION,synchronization=SynchronizationType.SYNCHRONIZED,unitName="CCPU")
    private EntityManager em;

@Override
public ArrayList<PGNotification> getNotifications(){

    Session session = em.unwrap(Session.class);

    PGNotification[] notifications = session.doReturningWork(new ReturningWork<PGNotification[]>() {

        @Override
        public PGNotification[] execute(Connection connection) throws SQLException {
            PGNotification[] notifications = ((PGConnection) connection).getNotifications();
            return notifications;
        }

    });

    return (ArrayList) Arrays.asList(notifications);
}   

}

- 更新
我修复了转发异常：

@Override
public ArrayList<PGNotification> getNotifications(){

    Session session = em.unwrap(Session.class);


    PGNotification[] notifications = session.doReturningWork(new ReturningWork<PGNotification[]>() {

        @Override
        public PGNotification[] execute(Connection connection) throws SQLException {

            PGConnection pgc = null; 

            if (connection.isWrapperFor(PGConnection.class)) {
                pgc = (PGConnection) connection.unwrap(PGConnection.class);
            }                               

            PGNotification[] notifications = pgc.getNotifications();                
            return notifications;
        }
    });

但似乎我仍然没有收到通知。

更新---
在我实施Neil提出的解决方案后，当我取消部署应用程序时，我在glassfish日志中出现此错误：

    2014-06-27T11:03:24.278+0300|SEVERE: The web application [/myApp] created a ThreadLocal    with key of type [io.netty.buffer.PooledByteBufAllocator$1] (value [io.netty.buffer.PooledByteBufAllocator$1@28ad6479]) and a value of type [io.netty.buffer.PoolThreadCache] (value [io.netty.buffer.PoolThreadCache@f9f58cc]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.279+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.Recycler$1] (value [io.netty.util.Recycler$1@267ec117]) and a value of type [io.netty.util.Recycler.Stack] (value [io.netty.util.Recycler$Stack@4bb6e0bf]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.279+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.Recycler$1] (value [io.netty.util.Recycler$1@535d426e]) and a value of type [io.netty.util.Recycler.Stack] (value [io.netty.util.Recycler$Stack@fb46e84]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.280+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.internal.ThreadLocalRandom$2] (value [io.netty.util.internal.ThreadLocalRandom$2@ec3a42a]) and a value of type [io.netty.util.internal.ThreadLocalRandom] (value [io.netty.util.internal.ThreadLocalRandom@4e4ec8f8]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.280+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.Recycler$1] (value [io.netty.util.Recycler$1@166c39f2]) and a value of type [io.netty.util.Recycler.Stack] (value [io.netty.util.Recycler$Stack@1b504a5e]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.281+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.Recycler$1] (value [io.netty.util.Recycler$1@34426f54]) and a value of type [io.netty.util.Recycler.Stack] (value [io.netty.util.Recycler$Stack@759b0e99]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.282+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.concurrent.DefaultPromise$1] (value [io.netty.util.concurrent.DefaultPromise$1@16db9b21]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.282+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.Recycler$1] (value [io.netty.util.Recycler$1@166c39f2]) and a value of type [io.netty.util.Recycler.Stack] (value [io.netty.util.Recycler$Stack@2ba59f40]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.282+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.buffer.PooledByteBufAllocator$1] (value [io.netty.buffer.PooledByteBufAllocator$1@28ad6479]) and a value of type [io.netty.buffer.PoolThreadCache] (value [io.netty.buffer.PoolThreadCache@67a3923]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.283+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.Recycler$1] (value [io.netty.util.Recycler$1@166c39f2]) and a value of type [io.netty.util.Recycler.Stack] (value [io.netty.util.Recycler$Stack@423d2c27]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.283+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.util.Recycler$1] (value [io.netty.util.Recycler$1@535d426e]) and a value of type [io.netty.util.Recycler.Stack] (value [io.netty.util.Recycler$Stack@3e1dd66a]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
2014-06-27T11:03:24.283+0300|SEVERE: The web application [/myApp] created a ThreadLocal with key of type [io.netty.buffer.PooledByteBufAllocator$1] (value [io.netty.buffer.PooledByteBufAllocator$1@28ad6479]) and a value of type [io.netty.buffer.PoolThreadCache] (value [io.netty.buffer.PoolThreadCache@18e7e902]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.

我必须提到在取消部署应用程序时调用destroy（）方法。 如果我使用visualVM进行间谍活动，则在取消部署应用程序后，该线程仍处于活动状态。

public void destroy(){

    try{
        Statement statement = pgConnection.createStatement();                  
        statement.addBatch("UNLISTEN xxxTest");
        statement.executeBatch();
        statement.close();          
    }catch(SQLException sqle)   {
        sqle.printStackTrace(); 
    }

}

Answer 1

1. 为什么你需要Hibernate？ 只需使用JDBC。 你可能想要发起一个应用程序范围的事件（也许是发送一个websocket msg或者破坏ehcache），如果你需要做一些事情，请订阅那个事件并用Hibernate做一些事情。

2. http://impossibl.github.io/pgjdbc-ng/是你的朋友。 不需要投票。

请参阅http://blog.databasepatterns.com/2014/04/postgresql-nofify-websocket-spring-mvc.html

Answer 2

Hibernate没有对PostgreSL通知的直接支持，因为这是一个特定的数据库功能，并非所有数据库供应商都支持它，并且它不适合ORM框架职责。

不过，您仍然可以尝试将其挂钩到当前正在运行的事务中。 您需要访问当前数据库连接， 添加监听挂钩 。

这可以通过Session.doWork（）支持来完成：

session.doWork(new Work() {
    @Override
    public void execute(Connection connection) throws SQLException {
        //add some statement if it's required
        PGNotification notifications[] = ((PGConnection) connection).getNotifications();           
    }
});