休眠连接使用

Question

我正在尝试进行休眠联接-该查询看似可行，但是当我尝试从返回的对象强制转换为该类型时，我希望它不起作用...我假设是因为它也具有联接表信息。

@Entity
@Table(name = "PSNG_SMRY")
public class PSNG_SMRY implements Serializable, Comparable<PSNG_SMRY>
{
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(generator="increment")
    @GenericGenerator(name="increment"  , strategy = "increment")
    @Printable
    public Integer SMRY_ID;
    public Integer DEV_ID;
    public Integer RPTD_TRN_ID;

        @OneToOne(mappedBy="smry", cascade=CascadeType.ALL)
        public TRN trn;

}

@Entity
@Table(name = "TRN")
public class TRN implements Serializable
{
    private static final long serialVersionUID = 1L;

    @Id
    public Integer TRN_ID;
        public String TRN_SCTN
        public String TRN_SYMB;

         @OneToOne
        @PrimaryKeyJoinColumn
        private PSNG_SMRY smry;
}

我在这里找到了这个一对一的映射示例- 链接

当我从休眠中获取对象时，我尝试将其强制转换为PSNG_SMRY，它将无法正常工作-我该如何进行联接，在其中我使用联接从TRN表中获得PSNG_SMRY信息和TRN_SYMB？

编辑：

我收到无效的[Ljava.lang.Object; cannot be cast to PSNG_SMRY异常- [Ljava.lang.Object; cannot be cast to PSNG_SMRY [Ljava.lang.Object; cannot be cast to PSNG_SMRY

查询代码：

//code  from some function that sets up all queries
String qQuery = "FROM PSNG_SMRY P, TRN T WHERE  T.TRN_ID = P.RPTD_TRN_ID and P.FIR_AXLE_PASD_DT > sysdate - :timeLimit and P.FIR_AXLE_PASD_DT < sysdate - 1/24 ORDER BY P.FIR_AXLE_PASD_DT";

hqlParamList.add(new HQLParams("timeLimit", timeLimit)); //some list to pass to hibernate and then parameterize the queury

result = queryDatabase(qQuery, q4Query, hqlParamList);



public QueryResult queryDatabase(String qQuery, String q4Query,
        List<HQLParams> params) {
    QueryResult results = new QueryResult();

    jwdsqa = new Connection("JWDSQA");
    jwds4qa = new Connection("JWDS4QA");

    results.qa = jwdsqa.retrieve(qQuery, params);
    results.qa4 = jwds4qa.retrieve(q4Query, params);

    return results;
}

编辑：这是连接类-它仅用于获取会话信息并执行所有休眠方式，例如获取数据...

public class Connection {

public static Logger logger = Logger.getLogger(Connection.class);

   Session session;
   String sessionName;

public Connection(String name){
session = HibernateUtil.getSessionFactory(name).openSession();

sessionName = name;
    if(session.isConnected()){
        //System.out.println(name + " - Connected");
    }
}

public Session getSession(){
    return session;
}

@SuppressWarnings("unchecked")
public List<Object> retrieve(String qry, List<HQLParams> paramList)
{
    Transaction transaction = null;
    List<Object> obj = null;

    try {
        transaction = session.beginTransaction();

        String queryString = qry;

        Query query = session.createQuery(queryString);

        if(paramList != null)
        {
            for(HQLParams param: paramList)
            {
                query.setParameter(param.paramName, param.params);
            }
        }


        List<Object> obj_ = query.list();
        obj = obj_;
        //session.getTransaction().commit();

    } catch (HibernateException ex) {
        ex.printStackTrace();
        logger.error(ex.getMessage() + "\n" + ex.getStackTrace());
        transaction.rollback();
    } catch (Exception ex) {
        System.err.println(ex.getMessage());
        logger.error(ex.getMessage() + "\n" + ex.getStackTrace());
    }
    finally
    {
        session.close();
        //System.out.println("Closing session " + sessionName);
    }

    return obj;
}
}

Answer 1

我最终弄清楚了这一点-我得到转换错误的原因是休眠的原因是将PSNG_SMRY和TRN对象都作为Object[]而不是作为一个Object返回。

Answer 2

如果您想要PSNG_SMRY实例，则不必要求TRN表。 当您使用JPA映射时为您提供

   FROM PSNG_SMRY P 
        WHERE P.FIR_AXLE_PASD_DT > sysdate - :timeLimit 
        and P.FIR_AXLE_PASD_DT < sysdate - 1/24 
        ORDER BY P.FIR_AXLE_PASD_DT

如果您没有获得检索到的PSNG_SMRY对象的TRN，则意味着存在映射错误，因为您正在告诉Hibernate如何在注释中检索PSNG_SMRY的TRN。

    @OneToOne(mappedBy="smry", cascade=CascadeType.ALL)
    public TRN trn;