我的代码:

    @Test
public void testAddRoleAndAddUser() {

    Role r = roleDao.findByProperty("name", "admin");
    if(r == null) {
        r = new Role();
        r.setName("admin");
        r.setDescription("Just administrator.");
        roleDao.save(r);
    }

    User u = dao.get(1l);
    Set<Role> roles = u.getRoleSet();
    logger.debug("Roles is null: " + (roles == null));
    roles.add(r);
    dao.save(u);
}

13:39:41,041 ERROR: org.hibernate.LazyInitializationException failed to lazily initialize a collection of role: xxx.entity.core.User.roleSet, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: xxx.entity.core.User.roleSet, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365) at org.hibernate.collection.PersistentSet.add(PersistentSet.java:212) at sg.com.junglemedia.test.dao.impl.hibernate.UserDaoTest.testAddRoleAndAddUser(UserDaoTest.java:40) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

有人帮忙吗？

最佳答案

在您的实体类中，当您声明从用户到角色的映射时，请尝试将 fetchType 指定为 EAGER。像这样的东西:

@OneToMany(fetch=FetchType.EAGER)
public Collection<Role> getRoleSet(){
 ...
}

更新: 最近收到的这个答案的评论让我重新审视这个。自从我回答以来已经有一段时间了，当时我才开始使用 Hibernate。 Rafael 和 Mukus 说的是有道理的。如果你有一个大集合，你不应该使用急切的获取。它联合选择映射到您的条目的所有数据并加载到内存。另一种方法是在每次需要处理相关集合时(即每次需要调用 getRoleSet 方法)仍然使用延迟获取并打开 Hibernate session 。这样，每次调用此方法时，Hibernate 都会对数据库执行选择查询，并且不会将集合数据保存在内存中。详情可以引用我的帖子:http://khuevu.github.io/2013/01/20/understand-hibernate.html

也就是说，这取决于您的实际用例。如果您的集合数据很小，并且您经常需要查询数据，那么您最好使用急切获取。我认为，在您的具体情况下，角色集合可能非常小，适合使用急切获取。

关于java - Hibernate:未能延迟初始化角色集合，没有 session 或 session 已关闭，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/3519059/