Spring Data JPA with ManyToOne save operation is throwing org.hibernate.PersistentObjectException
<p>I'm experimenting  with Spring Data JPA but having issues with saving ManyToOne relationship. </p>

<pre><code>@Entity
public class Customer {

 @Id
 @GeneratedValue(strategy=GenerationType.AUTO)
 private Long id;
 private String firstName;
 private String lastName;


 @ManyToOne(cascade=CascadeType.ALL)
 private Address homeAddress;

 protected Customer() {}
 // getters and setters ...
}
</code></pre>

<p>Many customers can have the same address :</p>

<pre><code> @Entity
 public class Address {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  private String postalCode;
  private String city;
  private String line1;
  private String line2;
  private String country;

  public Address() {
    // TODO Auto-generated constructor stub
  }

  // getters and setter 
}
</code></pre>

<p>CustomerRepository</p>

<pre><code>import org.springframework.data.jpa.repository.JpaRepository;

public interface CustomerRepository extends JpaRepository&lt;Customer, Long&gt;       {

List&lt;Customer&gt; findByLastName(String lastName);
List&lt;Customer&gt; findByHomeAddress(Address address);

}
</code></pre>

<p>Application</p>

<pre><code>@SpringBootApplication
public class Application {

private static final Logger log = LoggerFactory.getLogger(Application.class);

public static void main(String[] args) {
    SpringApplication.run(Application.class);
}

@Bean
public CommandLineRunner demo(CustomerRepository repository) {
    return (args) -&gt; {



        Address address1 = new Address("07093", "Brooklyn", "129 67th st", null, "USA");
        Address address2 = new Address("03333", "Qeeens", "333 67th st", null, "USA");
        // save a couple of customers
        Customer jack = new Customer("Jack", "Bauer");

        jack.setHomeAddress(address1);
        repository.save(jack);                  
        repository.save(new Customer("Chloe", "O'Brian",address1));

 }
}
</code></pre>

<p>So I tried to save two customers with the same address I get the following exception: </p>

<pre><code>Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: hello.Address; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: hello.Address
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:299) ~[spring-orm-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:244) ~[spring-orm-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:491) ~[spring-orm-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59) ~[spring-tx-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213) ~[spring-tx-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:147) ~[spring-tx-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:133) ~[spring-data-jpa-1.10.5.RELEASE.jar:na]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) ~[spring-aop-4.3.4.RELEASE.jar:4.3.4.RELEASE]
at com.sun.proxy.$Proxy60.save(Unknown Source) ~[na:na]
at hello.Application.lambda$0(Application.java:35) [classes/:na]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:800) [spring-boot-1.4.2.RELEASE.jar:1.4.2.RELEASE]
... 6 common frames omitted
</code></pre>

<p>How can I resolve this issue? you see full code at <a href="https://github.com/suleimana/spring-data-jpa" rel="nofollow noreferrer">this git location</a></p>