【发布时间】：2014-06-30 22:18:08
【问题描述】：
我在使用 JPA 和 Java 8 函数式编程时遇到了一个非常奇怪的问题。
我有一个 Student 和 Presentation 类，它们的关系是双向的。在 Java 7 中一切正常，但我刚刚切换到 Java 8。
这个有效（可见是私有的，没有设置器）：
public static void setAllVisible(boolean visible) {
for (Presentation presentation : new PresentationRepository().findAll()) {
presentation.visible = visible;
}
}
这崩溃：
public static void setAllVisible(boolean visible) {
new PresentationRepository().findAll().forEach(x -> x.visible = visible);
//same for new PresentationRepository().findAll().stream().forEach(x -> x.visible = visible);
}
多次给出此异常：
Exception in thread "main" Local Exception Stack:
Exception [EclipseLink-30005] (Eclipse Persistence Services - 2.5.1.v20130918-f2b9fc5): org.eclipse.persistence.exceptions.PersistenceUnitLoadingException
Exception Description: An exception was thrown while searching for persistence archives with ClassLoader: sun.misc.Launcher$AppClassLoader@4554617c
Internal Exception: javax.persistence.PersistenceException: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.5.1.v20130918-f2b9fc5): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [BachelorproefPU] failed.
Internal Exception: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.5.1.v20130918-f2b9fc5): org.eclipse.persistence.exceptions.ValidationException
Exception Description: [class models.users.Student] uses a non-entity [class models.planning.Presentation] as target entity in the relationship attribute [field presentation].
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 persistence.JPAEntityManager.getEntityManagerFactory(JPAEntityManager.java:45)
at models.repositories.Repository.<init>(Repository.java:23)
at models.repositories.UserRepository.<init>(UserRepository.java:15)
at main.DbInitializer.<init>(DbInitializer.java:27)
at main.DbInitializer.main(DbInitializer.java:23)
我很确定persistence.xml 配置正确（因为它可以在没有Java 8 的情况下工作）并且所有类都包含在内并具有@Entity。它也不是 Student 类，因为如果我将其注释掉，错误只会给出另一个类。
这是什么原因造成的？也许还值得一提的是，我偶尔会遇到编译崩溃，他们要求我将项目发送给 Oracle。
【问题讨论】：
标签： jpa functional-programming eclipselink java-8