使用JPA，Spring，Hibernate进行多个查询

Question

I have recently configured my first JPA, Spring and Hibernate app to manage Users and Roles.

I have used The crudRepository to create my queries. I have two Repositories, one for Users, and one for Roles.

Initially I Autowired my repositories to a Controller, then called them like this:

Role godRole = roleRepository.findByName(roleName);
User newUser = new User("me@me.net", "mARK");

newUser.addRole(godRole);

userRepository.save(newUser);

This resulted in an exception:

org.hibernate.PersistentObjectException: detached entity passed to persist: uk.org.rspca.secrets.entities.Role
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:139)
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:801)
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:794)
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener$1.cascade(JpaPersistEventListener.java:97)
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:350)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:293)
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161)
    at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:379)
    at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:319)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:296)
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161)
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:118)
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:460)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:294)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:194)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:137)
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:84)
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206)
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149)
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75)

I assume this is happening because each query is run in a separate session, therefore the by the time I try to add the Role to the User, the role is n longer attached to a session and because it has an Id it tries to do an insert instead of matching it with an existing Role.

I read that if the method carrying out the queries uses the @Transaction annotation that the queries would all run in the same session, this doesn't seem to have made a difference!

Can anyone she any light on how I should be trying to implement this behaviour, it seems like a fairly simple thing to want to be able to do!

applicationContext.xml

<tx:annotation-driven transaction-manager="transactionManager"/>
<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan" value="uk.co.secrets" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="showSql" value="true" />
            <property name="generateDdl" value="true" />
            <property name="databasePlatform" value="org.hibernate.dialect.Oracle10gDialect" />
        </bean>
    </property>
</bean>

<bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="jdbc/DBPool" />
</bean>

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
    <property name="dataSource" ref="dataSource" />
</bean>

<data:repositories base-package="uk.co.secrets.repositories" />

User.java

 @Entity
@Table(name="S_User")
public class User {

    @Id
    @Column(name="u_pk_id")
    //@GeneratedValue(strategy=GenerationType.AUTO)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "S_User_Seq")
    @SequenceGenerator(name = "S_User_Seq", sequenceName = "S_User_Seq", allocationSize = 1)
    private long id;

    @Column(name="u_username")
    private String username;

    @Column(name="u_name")
    private String name;

    @Column(name="u_last_login")
    private Date lastLoggedin;

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(name = "S_UserRole", joinColumns = {
        @JoinColumn(name="u_fk_id") },
            inverseJoinColumns = { @JoinColumn(name = "r_fk_id") })
    private Set<Role> userRoles = new HashSet<Role>();
}

Role.java

@Entity
@Table(name="S_Role")
public class Role {

    @Id
    @Column(name="r_pk_id")
    //@GeneratedValue(strategy=GenerationType.AUTO)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "S_Role_Seq")
    @SequenceGenerator(name = "S_Role_Seq", sequenceName = "S_Role_Seq", allocationSize = 1)
    private long id;

    @Column(name="r_name")
    private String name;

    @Column(name="r_desc")
    private String description;

    @Column(name="r_created")
    private Date dateCreated;

    @Column(name="r_modified")
    private Date dateModified;

    @Column(name="r_removed")
    private Date dateremoved;
}

Regards mARK

Answer 1

Your controller method should be annotated with @Transactional. In your code, new transaction is created when you invoke repository method and is closed after method completion.

Anyway, it's a bad practice to start transaction in controller. It's better to create some service layer(transactional) between your controller and dao layers.

Answer 2

CascadeType.ALL means all operations made on the User object will be made on the Role object.

In this case, SAVE operation is cascaded to object Role which is detached now. That's why hibernate throw exception.

I'm curious why the Role object is being detached from session. When you made method Transactional (default propagation.Requires so it should create new transaction if no exists) and get your Role you should still have the same session.

EDIT: I checked it on my project. You can't save an entity with id (especially when you have @GeneratedValue annotation). So you can't cascade persist operation to Role entity. So removing CascadeType.ALL is the only solution IMO. Of course you can set CascadeType.UPDATE, CascadeType.REMOVE and so on.