Question

我在Oracle DB和Hibernate中使用JavaEE / JPA托管事务，需要实现某种嵌套事务。据我所知，这样的东西不支持开箱即用，但我应该可以为此目的使用保存点。

根据https://stackoverflow.com/a/7626387/173689的建议，我尝试了以下内容：

@Transactional(value = TxType.REQUIRES_NEW)
public boolean doImport(Import importer, Row row) throws ImportRowFailedException {
    // stripped code ...
    // We need to try different possibilities from which one may succeed...
    // ...former failures must be rolled back!
    for (Possibility poss : importer.getPossibilities()) {
        if (this.tryPossibility(poss, row)) break;
    }
    // stripped code ...
}

public boolean tryPossibility(Possibility possibility, Row row) {
    try {
        Session session = this.em.unwrap(Session.class);
        session.doWork(new Work() {
            @Override
            public void execute(Connection connection) throws SQLException {
                Savepoint before = connection.setSavepoint();
                if (!possibility.importRow(row)) {
                    connection.rollback(before);
                    throw new ImportRowFailedException();
                }
            }
        });
    }
    catch (ImportRowFailedException ex) {
        return false;
    }
    return true;
}

在connection.rollback(before)后，我收到以下异常：

Caused by: java.sql.SQLException: IJ031040: Connection is not associated with a managed connection: org.jboss.jca.adapters.jdbc.jdk8.WrappedConnectionJDK8@40a6a460
    at org.jboss.jca.adapters.jdbc.WrappedConnection.lock(WrappedConnection.java:164)
    at org.jboss.jca.adapters.jdbc.WrappedConnection.rollback(WrappedConnection.java:883)

我该如何处理？

Answer 1

这是一个非常常见的问题，因此此答案基于我在博客上写的关于doWork和doReturningWork方法的this article。

问题是大多数JDBC驱动程序实际上并不支持嵌套事务。在您的情况下，您正在使用JBoss，它提供JTA事务管理器，但仍依赖JDBC提供程序提供的XA ResoureManager，如this forum thread中所述。

因此，最好使用doReturningWork而不是doWork并执行SQL SAVEPOINT命令，如下所示：

public boolean tryPossibility(Possibility possibility, Row row) {
    Session session = this.em.unwrap(Session.class);
    
    return session.doReturningWork(connection -> {
        connection.prepareStatement("SAVEPOINT IMPORT_ROW").executeUpdate();
        
        boolean importHasSuceed = possibility.importRow(row);
        
        if (!importHasSuceed) {
            connection.prepareStatement("ROLLBACK TO SAVEPOINT IMPORT_ROW").executeUpdate();
        }
        
        return importHasSuceed;
    });
}

有关Hibernate doWork和doReturningWork方法如何工作的更多详细信息，请查看this article。

Answer 2

The initial java.sql.SQLException: IJ031040 seems related to a specific outcome during our import. It later has been replaced with another java.sql.SQLException that forbid the rollback for managed transactions. But I could finally solve the problem by issuing native SQL statements:

// Mark the current state as SAVEPOINT...
Session session = this.em.unwrap(Session.class);
session.doWork(new Work() {
    @Override
    public void execute(Connection connection) throws SQLException {
        connection.prepareStatement("SAVEPOINT TRY_POSSIBILITY").executeUpdate();
    }
});

// 
// Do all the risky changes... verify... decide...
// 

// Rollback to SAVEPOINT if necessary!
session.doWork(new Work() {
    @Override
    public void execute(Connection connection) throws SQLException {
        connection.prepareStatement("ROLLBACK TO SAVEPOINT TRY_POSSIBILITY").executeUpdate();
    }
});

This allows a "nested Transaction" within the larger one and solved my problems.

如何使用Hibernate Session.doWork（...）进行保存点/嵌套事务？

2 个答案: