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，我需要使用一些 java 代码对一些数据库事件做出反应。
更准确地说，我想构建一个在向表中插入新行时使用 pg_notify() 的触发器。
我已经阅读了相关内容，但所有教程都使用直接 jdbc 连接，而不是通过休眠。
我（认为我）不能使用休眠事件，因为行不是通过休眠插入的，而是由第 3 方应用程序插入的。

有什么方法可以让我通过 hibernate 接收 pg_notify 发送的通知？

-- 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)

不得不提的是，我使用 Glassfish 4.0 作为 AS。连接池是在 glassfish 上创建的，应用程序通过 jndi 访问。 EntityManager 也是由带有 Spring 的容器注入的。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
我已经修复了 classcast 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;
        }
    });

但我似乎仍然没有收到通知。

更新---
在我实施了 Neil 提出的解决方案后，当我取消部署应用程序时，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.

我不得不提一下，在取消部署应用程序时会调用 destroy() 方法。 如果我使用 visualVM 进行监视，则在取消部署应用程序后线程仍然存在。

public void destroy(){

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

}

Answer 1

1. 为什么在这里需要休眠？只需使用 JDBC。无论如何，您可能都想触发一个应用程序范围的事件（可能发送一个 websocket msg 或破坏一个 ehcache），如果您需要做一些休眠的事情，请订阅该事件并使用休眠做一些事情。

   李>

2. http://impossibl.github.io/pgjdbc-ng/ 是你的朋友。无需投票。

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

Answer 2

Hibernate 不直接支持 PostgreSL 通知，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，并且不符合 ORM 框架的职责。

尽管如此，您仍然可以尝试将其挂接到您当前正在运行的事务中。你需要访问当前数据库连接做add the listening hook。

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();           
    }
});