使用 Hibernate Session.doWork 生成序列 ID

Question

Hibernate Session' doWork() method gives direct access to java.sql.Connection .

Following is one of the way to create and execute a PreparedStatement to generate sequence

public Long generateId() {
    final Long id[] = { null };

    getSessionFactory().openSession().doWork(new Work() {
        public void execute(Connection connection) throws SQLException {
            PreparedStatement ps = connection
                    .prepareStatement("SELECT HIB_SEQ.nextval FROM DUAL");
            ResultSet rs = ps.executeQuery();
            while (rs.next()) {
                id[0] = rs.getLong(0);
            }
        }
    });
    return id[0];
}

First, is there a better way to do this ?

Second Q do we need to explicitly close the PreparedStatement created above ?

Answer 1

An instance of PreparedStatement is created as part of method Work.execute and thus should be handled within that scope, including closing (an instance itself will be collected by GC once method finishes its execution since variable ps would become out of scope, but any external resources such as open cursor require an explicit call ps.close() ).

An instance of Connection on the other hand is passed into the method by Hibernate and should not be closed manually -- this is Hibernate's responsibility.

Answer 2

    String query = ((SessionFactoryImplementor)sessionFactory).getDialect().getSequenceNextValString(seqName);
    Session session = sessionFactory.getCurrentSession();
    return (Long) session.createSQLQuery(query).addScalar("nextval", Hibernate.LONG).uniqueResult();

You may want to tweak the scalar part a bit to fit your database's column name and return type.

Answer 3

1) For returning value we can use doReturningWork

public int updateEmployeeStatusWithCount(final List<String> employeeList) throws DBException
{
       Session session = null;
       try
       {
              session = HibernateUtil.getSession();
              session.beginTransaction();
              int cnt = session.doReturningWork(new ReturningWork<Integer>() {
                     @Override
                     public Integer execute(Connection conn) throws SQLException {
                           PreparedStatement pStmt = null;
                           try
                           {
                                  int updatedCnt = 0;
                                  String sqlQry = "UPDATE EMP_DETAILS set IS_ACTIVE='N' WHERE EMP_ID=?";
                                  pStmt = conn.prepareStatement(sqlQry);
                                  for(String empId:employeeList)
                                  {
                                         System.out.println(empId);
                                         pStmt.setString(1, empId);
                                         int cnt = pStmt.executeUpdate();
                                         updatedCnt+=cnt;
                                  }
                                  return updatedCnt;
                           }
                           finally
                           {
                                  pStmt.close();
                           }                                
                     }
              });
              session.getTransaction().commit();
              return cnt;
       }
       catch(HibernateException e)
       {
              throw new DBException("Error occured while updating Employee Status",e);
       }
       finally
       {
              HibernateUtil.closeSession(session);
       }            
}

2)Yes We have to explicitly close the PreparedStatement See below example

public void updateEmployeeStatus(final List<String> employeeList) throws DBException
{
       Session session = null;
       try
       {
              session = HibernateUtil.getSession();
              session.beginTransaction();
              session.doWork(new Work() {
                     @Override
                     public void execute(Connection conn) throws SQLException {
                           PreparedStatement pStmt = null;
                           try
                           {
                                  String sqlQry = "UPDATE EMP_DETAILS set IS_ACTIVE='N' WHERE EMP_ID=?";
                                  pStmt = conn.prepareStatement(sqlQry);
                                  for(String empId:employeeList)
                                  {
                                         pStmt.setString(1, empId);
                                         pStmt.addBatch();
                                  }
                                  pStmt.executeBatch();
                           }
                           finally
                           {
                                  pStmt.close();
                           }                                
                     }
              });
              session.getTransaction().commit();
       }
       catch(HibernateException e)
       {
              throw new DBException("Error occured while updating Employee Status",e);
       }
       finally
       {
              HibernateUtil.closeSession(session);
       }            
}

Reference