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向JPA实体添加额外方法

javajpa
4
我想在我的用户实体中添加一个方法，该方法返回其他实体的列表，这是用户实体中的字段，但经过筛选。问题是，当我将这样的方法添加到实体类中时，我会出现错误。
错误信息为：[类entities.WorksOnTask]在关系属性[字段user]中使用了非实体[类entities.User]作为目标实体。
为什么会出现这种情况？我如何在User实体类中添加返回（经过筛选的）WorksOnTask列表的方法？
还是说我应该采取其他措施？
@Entity
@Table(name = "user")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "User.findAll", query = "SELECT u FROM User u"),
    @NamedQuery(name = "User.findByUsername", query = "SELECT u FROM User u WHERE u.username = :username"),
    @NamedQuery(name = "User.findByPassword", query = "SELECT u FROM User u WHERE u.password = :password"),
    @NamedQuery(name = "User.findByFirstName", query = "SELECT u FROM User u WHERE u.firstName = :firstName"),
    @NamedQuery(name = "User.findByLastName", query = "SELECT u FROM User u WHERE u.lastName = :lastName"),
    @NamedQuery(name = "User.findByAppPrivileges", query = "SELECT u FROM User u WHERE u.appPrivileges = :appPrivileges"),
    @NamedQuery(name = "User.findByActivated", query = "SELECT u FROM User u WHERE u.activated = :activated")})
public class User implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @Column(name = "Username")
    private String username;
    @Basic(optional = false)
    @Column(name = "Password")
    private String password;
    @Basic(optional = false)
    @Column(name = "FirstName")
    private String firstName;
    @Basic(optional = false)
    @Column(name = "LastName")
    private String lastName;
    @Basic(optional = false)
    @Column(name = "AppPrivileges")
    private int appPrivileges;
    @Basic(optional = false)
    @Column(name = "Activated")
    private boolean activated;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "user", fetch = FetchType.LAZY)
    private List<WorksOnProject> worksOnProjectList;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "user", fetch = FetchType.LAZY)
    private List<WorksOnTask> worksOnTaskList;
public List<WorksOnTask> getWorksOnTaskList(){
    return worksOnTaskList;
}

public void setWorksOnTaskList(List<WorksOnTask> worksOnTaskList) {
    this.worksOnTaskList = worksOnTaskList;
}
public List<WorksOnTask> findWorksOnTaskListNonRemoved(){
    return new  ArrayList(worksOnTaskList).stream().filter((w)->!w.getRemoved()).collect(Collectors.toList());
}

堆栈跟踪显示了与用户相同的实体任务错误，但是一切都相同。
Exception in Application start method
java.lang.reflect.InvocationTargetException     at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)     at
com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:363)
    at
com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:303)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)  at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)     at
sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start
method  at
com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:875)
    at
com.sun.javafx.application.LauncherImpl.lambda$launchApplication$147(LauncherImpl.java:157)
    at
com.sun.javafx.application.LauncherImpl$$Lambda$53/200006406.run(Unknown
Source)     at java.lang.Thread.run(Thread.java:745) Caused by: Exception
[EclipseLink-30005] (Eclipse Persistence Services -
2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.PersistenceUnitLoadingException
Exception Description: An exception was thrown while searching for
persistence archives with ClassLoader:
sun.misc.Launcher$AppClassLoader@55f96302 Internal Exception:
javax.persistence.PersistenceException: Exception [EclipseLink-28018]
(Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd):
org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [DBPU] failed.
Internal Exception: Exception [EclipseLink-7250] (Eclipse Persistence
Services - 2.5.2.v20140319-9ad6abd):
org.eclipse.persistence.exceptions.ValidationException Exception
Description: [class entities.Project] uses a non-entity [class
entities.Task] as target entity in the relationship attribute [field
iDRootTask].    at
org.eclipse.persistence.exceptions.PersistenceUnitLoadingException.exceptionSearchingForPersistenceResources(PersistenceUnitLoadingException.java:127)
    at
org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactoryImpl(PersistenceProvider.java:107)
    at
org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:177)
    at
javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)
    at
javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
    at pg.jpa.JpaAccessManager.<init>(JpaAccessManager.java:24)     at
pg.Login.start(Login.java:49)   at
com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$153(LauncherImpl.java:821)
    at
com.sun.javafx.application.LauncherImpl$$Lambda$56/574011920.run(Unknown
Source)     at
com.sun.javafx.application.PlatformImpl.lambda$runAndWait$166(PlatformImpl.java:323)
    at
com.sun.javafx.application.PlatformImpl$$Lambda$50/1768305536.run(Unknown
Source)     at
com.sun.javafx.application.PlatformImpl.lambda$null$164(PlatformImpl.java:292)
    at
com.sun.javafx.application.PlatformImpl$$Lambda$52/1148099840.run(Unknown
Source)     at java.security.AccessController.doPrivileged(Native Method)
    at
com.sun.javafx.application.PlatformImpl.lambda$runLater$165(PlatformImpl.java:291)
    at
com.sun.javafx.application.PlatformImpl$$Lambda$51/1146743572.run(Unknown
Source)     at
com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)  at
com.sun.glass.ui.gtk.GtkApplication.lambda$null$45(GtkApplication.java:126)
    at
com.sun.glass.ui.gtk.GtkApplication$$Lambda$42/379110473.run(Unknown
Source)     ... 1 more Caused by: javax.persistence.PersistenceException:
Exception [EclipseLink-28018] (Eclipse Persistence Services -
2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [DBPU] failed.
Internal Exception: Exception [EclipseLink-7250] (Eclipse Persistence
Services - 2.5.2.v20140319-9ad6abd):
org.eclipse.persistence.exceptions.ValidationException Exception
Description: [class entities.Project] uses a non-entity [class
entities.Task] as target entity in the relationship attribute [field
iDRootTask].    at
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.createPredeployFailedPersistenceException(EntityManagerSetupImpl.java:1954)
    at
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:1945)
    at
org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.callPredeploy(JPAInitializer.java:98)
    at
org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactoryImpl(PersistenceProvider.java:96)
    ... 19 more Caused by: Exception [EclipseLink-28018] (Eclipse
Persistence Services - 2.5.2.v20140319-9ad6abd):
org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [DBPU] failed.
Internal Exception: Exception [EclipseLink-7250] (Eclipse Persistence
Services - 2.5.2.v20140319-9ad6abd):
org.eclipse.persistence.exceptions.ValidationException Exception
Description: [class pentities.Project] uses a non-entity [class
entities.Task] as target entity in the relationship attribute [field
iDRootTask].    at
org.eclipse.persistence.exceptions.EntityManagerSetupException.predeployFailed(EntityManagerSetupException.java:230)
    ... 23 more Caused by: Exception [EclipseLink-7250] (Eclipse
Persistence Services - 2.5.2.v20140319-9ad6abd):
org.eclipse.persistence.exceptions.ValidationException Exception
Description: [class entities.Project] uses a non-entity [class
entities.Task] as target entity in the relationship attribute [field
iDRootTask].    at
org.eclipse.persistence.exceptions.ValidationException.nonEntityTargetInRelationship(ValidationException.java:1378)
    at
org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.RelationshipAccessor.getReferenceDescriptor(RelationshipAccessor.java:553)
    at
org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ObjectAccessor.processForeignKeyRelationship(ObjectAccessor.java:659)
    at
org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ObjectAccessor.processOwningMappingKeys(ObjectAccessor.java:733)
    at
org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ManyToOneAccessor.process(ManyToOneAccessor.java:123)
    at
org.eclipse.persistence.internal.jpa.metadata.MetadataProject.processOwningRelationshipAccessors(MetadataProject.java:1580)
    at
org.eclipse.persistence.internal.jpa.metadata.MetadataProject.processStage3(MetadataProject.java:1833)
    at
org.eclipse.persistence.internal.jpa.metadata.MetadataProcessor.processORMMetadata(MetadataProcessor.java:580)
    at
org.eclipse.persistence.internal.jpa.deployment.PersistenceUnitProcessor.processORMetadata(PersistenceUnitProcessor.java:585)
    at
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:1869)
    ... 21 more Exception running application pg.Login
不要使用这个方法，它只是一个方便的方法。 - Marko
我需要切换分支并返回到出现问题的提交。等一下。 - Marko
2
很奇怪，你刚添加了那个方法后就出现了这个异常，似乎两者之间没有关系。你可以尝试使用旧的方式实现该方法，而不是使用Java 8的特性吗？此外，对于worksOnTaskList，请使用getter而不是直接字段访问。 - Predrag Maric
我知道你已经解决了，我只是好奇最初导致问题的原因。还有，nema na čemu :) - Predrag Maric
很奇怪，我想知道是否已经有人报告了这个 bug，因为在我看来它看起来像是一个 bug。 - Predrag Maric
显示剩余6条评论
2个回答
4
我找到了这个问题的一种答案。问题是似乎我无法在该方法中访问实体类的映射字段。但我已经使用查询得到了我想要的信息。
所以我现在没有问题了，但仍然在寻找答案。
编辑： 好吧，似乎在属于实体类的方法中使用 lambda 表达式会出现问题。
例如，这样做行不通：
public List<WorksOnTask> getWorksOnTaskListNonRemoved() {
    ArrayList<WorksOnTask> wots =  new ArrayList<>(worksOnTaskList);
    wots.removeIf((w)->w.getRemoved());
    return wots;
}

但是这样做可以使应用程序启动而没有错误：
public List<WorksOnTask> getWorksOnTaskListNonRemoved() {
    ArrayList<WorksOnTask> wots =  new ArrayList<>(worksOnTaskList);
    wots.removeIf(new Predicate<WorksOnTask>(){

        @Override
        public boolean test(WorksOnTask t) {
            return t.getRemoved();
        }

    });

    return wots;
}

这并不是Java 8流和lambda不能很好地协同工作的唯一情况。 流无法处理实体的IndirectLists。因此，当我将它们结合使用时，我需要编写类似于以下内容的代码：

new ArrayList<>(user.getWorksOnTaskList()).stream().....

改为：

user.getWorksOnTaskList().stream()......

很遗憾，我更喜欢流操作而不是JPA。

1
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