detached entity passed to persist: Profile
<p>I've the following two entities:</p>

<pre><code>@Entity
public class Profile implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue
    private int id;

    @OneToOne
    @JoinColumn(nullable = false, name = "USERNAME_FK")
    private RegisteredUser user;

    ...
</code></pre>

<p>and </p>

<pre><code>@Entity
public class RegisteredUser implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    private int id;

    @OneToOne
    @JoinColumn(nullable = false, name = "USERNAME_FK")
    private User user;

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "user")
    private Profile profile;
    ...
</code></pre>

<p>I'm using "repositories" and hibernate to store entities to the database. I would like that my entities are as much robust as possible by using annotations, but this is only causing me a lot of problems.</p>

<p>Currently, I've the following code:</p>

<pre><code>@Autowired
private RegisteredUserRepository rur;

@Autowired
private UserRepository ur;
...

// Creating a user
User root = new User("root", "1234", "root@root.com");
root.setFirstName("root");
root.setLastName("root");
root = ur.save(root);

Profile profile = new Profile(String.format("%s", root.getFullName()));

RegisteredUser registeredUser = new RegisteredUser(profile);
root.setRegisteredUser(registeredUser);
registeredUser = rur.save(registeredUser);
registeredUser = rur.save(registeredUser); // PROBLEM HERE!
</code></pre>

<p>The traceback of the problem is:</p>

<pre><code>Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist: com.mycompany.app.models.Profile
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:139) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:801) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:794) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener$1.cascade(JpaPersistEventListener.java:97) ~[hibernate-entitymanager-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:350) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:293) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:118) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:470) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:295) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:195) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:138) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:84) ~[hibernate-entitymanager-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:784) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1181) ~[hibernate-entitymanager-4.3.11.Final.jar:4.3.11.Final]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_40]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_40]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_40]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_40]
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:294) ~[spring-orm-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at com.sun.proxy.$Proxy88.persist(Unknown Source) ~[na:na]
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:439) ~[spring-data-jpa-1.9.4.RELEASE.jar:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_40]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_40]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_40]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_40]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:483) ~[spring-data-commons-1.11.4.RELEASE.jar:na]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:468) ~[spring-data-commons-1.11.4.RELEASE.jar:na]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:440) ~[spring-data-commons-1.11.4.RELEASE.jar:na]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61) ~[spring-data-commons-1.11.4.RELEASE.jar:na]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99) ~[spring-tx-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281) ~[spring-tx-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96) ~[spring-tx-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136) ~[spring-tx-4.2.5.RELEASE.jar:4.2.5.RELEASE]
    ... 21 common frames omitted
</code></pre>

<p>What I was trying to accomplish is that when I try to save the second time the registered user, it would update the tables correctly.</p>

<p>How can I solve this problem? I've seen that it may be because of how I implemented the setters and getters, so there they are:</p>

<p>Getters and setters in the class <code>RegisteredUser</code>:</p>

<pre><code>public Profile getProfile() {
    return profile;
}

public void setProfile(Profile profile) {
    if (sameAsFormer(profile)) {
        return;
    }

    Profile oldProfile = this.profile;
    this.profile = profile;

    if (oldProfile != null) {
        oldProfile.setRegisteredUser(null);
    }

    if (this.profile != null) {
        this.profile.setRegisteredUser(this);
    }
}
</code></pre>

<p>Setters and getters in <code>Profile</code>:</p>

<pre><code>public RegisteredUser getRegisteredUser() {
    return user;
}

public void setRegisteredUser(RegisteredUser u) {
    user = u;
}
</code></pre>