各位高手，我在使用hibernate、jpa、springdata集成时遇到了如下的问题：

1.model

@Entity @Table(name="group",schema="sc") @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) public class Group extends AbstractEntity { ... @ElementCollection(fetch= FetchType.EAGER) @NotNull @Column(name="user") @CollectionTable(name = "t_group_users", schema = "sc", joinColumns = @JoinColumn(name = "group_id")) private List users; }

2.repository

public interface GroupRepository extends CrudRepository { }

3.config

@Configuration @EnableJpaRepositories(basePackages = { "com.**.**" }) public class RepositoryTestConfig { @Bean public PlatformTransactionManager transactionManager(EntityManagerFactory emf) { JpaTransactionManager transactionManager = new JpaTransactionManager(); transactionManager.setEntityManagerFactory(emf); return transactionManager; } @Bean public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) { LocalContainerEntityManagerFactoryBean emfb = new LocalContainerEntityManagerFactoryBean(); emfb.setDataSource(dataSource()); emfb.setJpaVendorAdapter(jpaVendorAdapter()); emfb.setPackagesToScan("com.**.**.model"); Properties properties = new Properties(); properties.setProperty("hibernate.hbm2ddl.auto", "create"); properties.setProperty("hibernate.format_sql", "true"); emfb.setJpaProperties(properties); return emfb; } @Bean public JpaVendorAdapter jpaVendorAdapter() { HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter(); adapter.setDatabase(Database.H2); adapter.setShowSql(false); adapter.setGenerateDdl(false); adapter.setDatabasePlatform("org.hibernate.dialect.H2Dialect"); return adapter; } @Bean(name = "testFunctionDataSource") public DataSource dataSource() { DriverManagerDataSource dataSource = new DriverManagerDataSource(); dataSource.setDriverClassName("org.h2.Driver"); dataSource.setUrl("jdbc:h2:~/test;INIT=CREATE SCHEMA IF NOT EXISTS sc"); dataSource.setUsername("sa"); dataSource.setPassword(""); return dataSource; } }

但我使用groupRepository.findOne方法时，users返回的是org.hibernate.collection.internal.PersistentBag类型，而不是ArrayList类型，请问是什么原因？