java - 使用 Hibernate 继承时的问题

Question

我正在做一个小练习，在调用选择查询时遇到了一些问题。

基本上我通过以下方式创建了一个抽象类：

//AbstractStage
entity --class ~.AbstractStage --mappedSuperclass  --abstract 
field date --fieldName datetime --type java.util.Date --notNull
field boolean --fieldName iscomplete --type java.util.boolean

和两个子类如下：

//
// HappyStage
//
entity --table happy_stage --class ~.HappyStage --extends  ~.AbstractStage --testAutomatically --identifierField id --identifierColumn id_happy_stage
field boolean --fieldName isSad --type java.util.boolean
field date --fieldName dateOfDeath --type java.util.Date --notNull
finder add findHappyStagesByIscomplete

和

   //
   // HStage
   //
   entity --table h_stage --class ~.HStage --extends ~.AbstractStage  --testAutomatically --identifierField id --identifierColumn id_h_stage
    field boolean --fieldName isHappy --type java.util.boolean
    field date --fieldName dateOfBirth --type java.util.Date --notNull

我的环境是：

Java
SpringTool
Roo
Hibernate

我还运行了一个持久化 roo 命令：

persistence setup --provider HIBERNATE --database MYSQL

然后我编写了控制器类如下：

package test;

import java.util.Date;

import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;

import org.springframework.roo.addon.web.mvc.controller.RooWebScaffold;
import test.HappyStage;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.stereotype.Controller;

@RooWebScaffold(path = "happystages", formBackingObject = HappyStage.class)
@RequestMapping("/happystages")
@Controller
public class HappyStageController {

 @RequestMapping(value="/happy", method=RequestMethod.GET)
 public String get() throws Exception
 {

 // TypedQuery<AbstractStage> queryResults = HappyStage.findAbstractStagesByIscomplete(true);
  Date dd = new Date();
  TypedQuery<AbstractStage> queryResults = HappyStage.findAbstractStagesByDateGreaterThan(dd);

  System.err.println("N.of abstractstages found: " + queryResults.getResultList().size());
  return "redirect:/InheritanceTest";  
 }  

}

HappyStage 有方法 findAbstractStagesByDateGreaterThan。想法是从子类中调用此方法并获取日期大于的所有抽象阶段。

q = em.createQuery("FROM test.AbstractStage AS abstractstage WHERE abstractstage.datetime > :datetime", AbstractStage.class);

这是 HappyStage 类的代码：

package test;

import test.AbstractStage;
import org.springframework.roo.addon.javabean.RooJavaBean;
import org.springframework.roo.addon.tostring.RooToString;
import org.springframework.roo.addon.entity.RooEntity;
import java.util.Date;
import javax.validation.constraints.NotNull;
import javax.persistence.EntityManager;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.TypedQuery;
import org.springframework.format.annotation.DateTimeFormat;

@RooJavaBean
@RooToString
@RooEntity(identifierField = "id", identifierColumn = "id_happy_stage", table = "happy_stage", finders = { "findHappyStagesByIscomplete", "findHappyStagesByDatetimeGreaterThan" })
public class HappyStage extends AbstractStage {

    private Boolean isSad;

    @NotNull
    @Temporal(TemporalType.TIMESTAMP)
    @DateTimeFormat(style = "S-")
    private Date dateOfDeath;

    public static TypedQuery<AbstractStage> findAbstractStagesByIscomplete(Boolean iscomplete) throws Exception {
        if (iscomplete == null) throw new IllegalArgumentException("The iscomplete argument is required");
        EntityManager em = HappyStage.entityManager();
        TypedQuery<AbstractStage> q = null;
        try {
            q = em.createQuery("FROM test.AbstractStage AS abstractstage WHERE abstractstage.iscomplete = :iscomplete", AbstractStage.class);
          q.setParameter("iscomplete", iscomplete);

        } catch (Exception exp) {
          System.err.println("Ex message:\n" + exp + "\nStack trace \n" );

          int stLenght =  exp.getStackTrace().length;
          StackTraceElement [] ste = exp.getStackTrace();
         for(int i=0; i<stLenght; i++){
           System.err.println("message [" + i + "]" + ste[i].toString());          
         }
            throw(exp);

        }
        return q;
    }


    public static TypedQuery<AbstractStage> findAbstractStagesByDateGreaterThan(Date datetime) throws Exception {

        EntityManager em = HappyStage.entityManager();
        TypedQuery<AbstractStage> q = null;
        try { 
            q = em.createQuery("FROM test.AbstractStage AS abstractstage WHERE abstractstage.datetime > :datetime", AbstractStage.class);
         q.setParameter("datetime", datetime);

        } catch (Exception exp) {
            System.err.println("Ex message:\n" + exp);
            throw(exp);
        }
        return q;
    }    

}

问题是，当我在服务器上运行代码并转到 * /happystages/happy时，我得到一个带有以下堆栈跟踪的 nullPointer 异常：。*

org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:281)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:365)
$Proxy48.createQuery(Unknown Source)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
$Proxy49.createQuery(Unknown Source)
test.HappyStage.findAbstractStagesByDateGreaterThan_aroundBody2(HappyStage.java:55)
test.HappyStage.findAbstractStagesByDateGreaterThan(HappyStage.java:1)
test.HappyStageController.get(HappyStageController.java:25)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:113)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.traceNextValve(HttpRequestOperationCollectionValve.java:90)
com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.invoke(HttpRequestOperationCollectionValve.java:76)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:409)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
java.lang.Thread.run(Thread.java:680)

运行 JUnit 测试，我们发现异常中的错误可能与 Hibernate 如何处理 SQL 查询有关。添加一些断点我们发现这可能是涉及的代码：

/**
 * Abstract implementation of the Query interface.
 *
 * @author Gavin King
 * @author Max Andersen
 */

public abstract class AbstractQueryImpl implements Query {

....
 public Type[] getReturnTypes() throws HibernateException {
  return session.getFactory().getReturnTypes( queryString );
 }

...
}

我们现在正在进一步分解代码，但 *我想知道你们中是否有人已经遇到过类似的问题。有什么我想念的吗？可以将抽象类作为父类还是有必要将其作为“具体”类？*在我看来，您不能拥有一个抽象类并对其进行扩展，然后使用它通过基于继承值的查询来查询所有子类，这对我来说似乎很奇怪。

请要求我澄清，因为我的问题可能没有得到正确解释。

此致

PS：我也尝试过在 AbstractClass 中不使用 --Abstract 关键字。它仍然不起作用，并在去happystages/happy并触发get方法时给了我这个expetion（调用：TypedQuery queryResults = HappyStage.findAbstractStagesByDateGreaterThan(dd) ;）“

org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:281)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:365)
$Proxy48.createQuery(Unknown Source)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
$Proxy49.createQuery(Unknown Source)
test.HappyStage.findAbstractStagesByDateGreaterThan_aroundBody2(HappyStage.java:55)
test.HappyStage.findAbstractStagesByDateGreaterThan(HappyStage.java:1)
test.HappyStageController.get(HappyStageController.java:25)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:113)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.traceNextValve(HttpRequestOperationCollectionValve.java:90)
com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.invoke(HttpRequestOperationCollectionValve.java:76)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:409)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
java.lang.Thread.run(Thread.java:680)

似乎它与 MySQl 和 Abstract 无关，因为我还将 hibernate 使用的方言 SQL 查询翻译成真正的 SQL 查询，并直接在 MySQL shell 上运行它

Answer 1

我现在实际上已经尝试通过删除映射的超类标签，它似乎正在工作。我找到了这个答案，似乎解决了这个问题：

Hibernate ManyToMany和超类映射问题

虽然 roo 1.0.1 有一个小错误，并且有人在 spring 社区论坛上发布了这个问题：

http://forum.springsource.org/showthread.php?p=333182#post333182