Java 休眠自定义多字段选择

我们有以下几种型号

@Entity
@Cacheable
@org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Person {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    public int id;

    @Column(nullable = false, columnDefinition = "text")
    public String name;

    @Column(nullable = false, unique = true)
    public long ssid;

    @Column(nullable = false)
    public int age;

    @Column(nullable = false)
    public long registration;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "person")
    @Cascade(CascadeType.ALL)
    public List<Car> cars;


}

织物模型

@Entity
@Cacheable
@org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Fabric {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    public int id;


    @Column(nullable = false, columnDefinition = "text")
    public String name;


    @OneToMany(fetch = FetchType.LAZY, mappedBy = "fabric")
    @Cascade(CascadeType.ALL)
    public List<Car> cars;
}

我们会犯错误。有人能帮忙吗

   org.springframework.web.util.NestedServletException: Request processing failed; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
        org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:982)
        org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
        org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
        org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
        org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71)

org.hibernate.exception.SQLGrammarException: could not extract ResultSet
    org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:63)
    org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
    org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:97)
    org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:79)
    org.hibernate.loader.Loader.getResultSet(Loader.java:2123)
    org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1911)
    org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1887)
    org.hibernate.loader.Loader.doQuery(Loader.java:932)
    org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:349)
    org.hibernate.loader.Loader.doList(Loader.java:2615)
    org.hibernate.loader.Loader.doList(Loader.java:2598)
    org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2430)
    org.hibernate.loader.Loader.list(Loader.java:2425)
    org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:502)
    org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:370)
    org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:216)
    org.hibernate.internal.SessionImpl.list(SessionImpl.java:1481)
    org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1441)
    org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1410)
    org.hibernate.Query.getResultList(Query.java:427)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:498)
    org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333)
    org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    com.sun.proxy.$Proxy88.getAllPostOverview(Unknown Source)
    jarvis.api.story.PostController.getAllPostOverviews(PostController.java:51)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:498)
    org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:220)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71)

---

不要将

cars

指定为查询中的字段

尝试添加

LEFT JOIN FETCH

子句，将在单个查询中加载具有已加入的关联集合的个人实体：

SELECT p.name FROM Person p LEFT JOIN FETCH p.cars ORDER BY p.registration DESC

---

JPA不支持按照你的要求去做，至少不支持你试图走的路。但是如果您从

汽车的角度来处理问题，您可以

SELECT c, c.person.name FROM Car c ORDER BY c.person.registration DESC

如果要将此结果集自动填充到值对象中，可以使用
selectnew
语法，也可以使用JPA
CriteriaBuilder#construct
方法

SELECT NEW MyValueObject( c, c.person.name )
FROM Car c 
ORDER BY c.person.registration DESC

然后，您可以将
列表
与Java Stream API结合起来，并根据需要在内存中对结果进行分组

只需了解您获得的结果集包含：


汽车
实例
一个
字符串
实例，其中包含
人员
的名称值

更新

为了构建关联的
Car
的映射，我可能会在
MyValueObject
中添加传递
c.person.id
作为另一个构造函数参数，以防遇到两个同名的人的情况

List<MyValueObject> queryResults = query.getResultList();
List<List<MyValueObject>> groupedResults = queryResults
  .stream()
  .collect( Collectors.groupingBy( MyValueObject::getPersonId ) )
  .values();

List queryResults=query.getResultList（）；
List groupedResults=queryResults
.stream（）
.collect（收集器.groupingBy（MyValueObject:：getPersonId））
.values（）；

groupedResults
中的每个条目都是与给定的
Person
关联的
Car
实例列表，包装为
MyValueObject
实例
 你可以试试这个

session.createQuery("Select ps.name from Person as ps JOIN FETCH ps.cars ORDER BY ps.registration DESC");

你能提供完整的堆栈跟踪以便我们看到根本原因吗？还要添加Car实体code@MaciejKowalski我已经上传了关于erro的完整跟踪的模型，@raigeki？@Naros我上传了StackTraceth这并不能解决OP只想获取特定列作为结果集有效载荷的一部分的问题。而且编辑的结果只返回名称，而不是他们想要的名称~和~汽车集合。不，我已经尝试过了。简而言之，
LEFT JOIN FETCH
避免了编译时指定的
FETCH=FetchType.LAZY
，并强制加载汽车。我需要将人名和他/她的汽车列为集合
List<MyValueObject> queryResults = query.getResultList();
List<List<MyValueObject>> groupedResults = queryResults
  .stream()
  .collect( Collectors.groupingBy( MyValueObject::getPersonId ) )
  .values();

session.createQuery("Select ps.name from Person as ps JOIN FETCH ps.cars ORDER BY ps.registration DESC");