Spring data JPA and hibernate detached entity passed to persist on ManyToMany relationship

Question

I am trying to persist an object that has a many-to-many relationship with other objects already persisted.

Here is my persisted object (they are already persisted in the db, which is a MySql):-

Product

@Entity @Table(name="PRODUCT") public class Product {     private int productId;     private String productName;     private Set<Reservation> reservations = new HashSet<Reservation>(0);      @Id @GeneratedValue(strategy=GenerationType.AUTO)     public int getProductId() {         return productId;     }      public void setProductId(int productId) {         this.productId = productId;     }  @Column(nullable = false)     public String getProduct() {         return product;     }     public void setProduct(String product) {         this.product = product;     }      @ManyToMany(fetch = FetchType.LAZY, mappedBy = "products")     public Set<Reservation> getReservations() {         return reservations;     }     public void setReservations(Set<Reservation> reservations) {         this.reservations = reservations;     } } 

Here is my no persisted object, which I am trying to create

@Entity @Table(name = "RESERVATION") public class Reservation {      private int reservationId;      private Set<Product> products = new HashSet<Product>(0);      @Id     @GeneratedValue(strategy = GenerationType.AUTO)     public int getReservationId() {         return reservationId;     }      public void setReservationId(int reservationId) {         this.reservationId = reservationId;     }      @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)     @JoinTable(name = "product_reservation", joinColumns = { @JoinColumn(name = "reservationId", nullable = false, updatable = false) }, inverseJoinColumns = { @JoinColumn(name = "productId",              nullable = false, updatable = false) })     public Set<Product> getProducts() {         return products;     }      public void setProducts(Set<Product> products) {         this.products = products;     } } 

This is my ReservationService class, which receives an array of products names, look the products using the name and put them into the reservation object.

@Service public class ReservationServiceImpl implements ReservationService {      @Autowired     private ProductDAO productDAO;     @Autowired     private ReservationDAO reservationDAO;      @Transactional     public void createReservation(String[] productNames) {              Set<Product> products = new HashSet<Product>();             for (String productName : productNames) {                 Product pi = productDAO.findByProductName(productName);                 products.add(pi);             }             Reservation reservation = new Reservation();             reservation.setProducts(products);             reservationDAO.save(reservation);   ---> Here I am getting detached entity passed to persist     } } 

Here is my ProductDAO interface:

public interface ProductDAO extends JpaRepository<Product, Integer> {      public Product findByProductName(String productName); } 

This is my spring config file:

@Configuration @PropertySource(value = { "classpath:base.properties" }) @EnableTransactionManagement @EnableJpaRepositories(basePackages = "com.reservation.dao") public class RepositoryConfig {      @Autowired     private Environment env;      @Bean     public static PropertySourcesPlaceholderConfigurer placeHolderConfigurer() {         return new PropertySourcesPlaceholderConfigurer();     }      @Bean     public PlatformTransactionManager transactionManager() {         EntityManagerFactory factory = entityManagerFactory().getObject();         return new JpaTransactionManager(factory);     }      @Bean     public LocalContainerEntityManagerFactoryBean entityManagerFactory() {         HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();         vendorAdapter.setGenerateDdl(Boolean.valueOf(env                 .getProperty("hibernate.generate.ddl")));         vendorAdapter.setShowSql(Boolean.valueOf(env                 .getProperty("hibernate.show_sql")));          Properties jpaProperties = new Properties();         jpaProperties.put("hibernate.hbm2ddl.auto",                 env.getProperty("hibernate.hbm2ddl.auto"));         jpaProperties.put("hibernate.dialect", env.getProperty("hibernate.dialect"));          LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();         factory.setDataSource(dataSource());         factory.setJpaVendorAdapter(vendorAdapter);         factory.setPackagesToScan("com.reservation.service.domain");         factory.setJpaProperties(jpaProperties);         factory.afterPropertiesSet();         factory.setLoadTimeWeaver(new InstrumentationLoadTimeWeaver());         return factory;     }      @Bean     public HibernateExceptionTranslator hibernateExceptionTranslator() {         return new HibernateExceptionTranslator();     }      @Bean     public DataSource dataSource() {         BasicDataSource dataSource = new BasicDataSource();         dataSource.setDriverClassName(env.getProperty("jdbc.driverClassName"));         dataSource.setUrl(env.getProperty("jdbc.url"));         dataSource.setUsername(env.getProperty("jdbc.username"));         dataSource.setPassword(env.getProperty("jdbc.password"));         return dataSource;     } } 

Here is the full stack trace:

SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/web] threw exception [Request processing failed; nested exception is org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: com.reservation.service.domain.Product; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: com.reservation.service.domain.Product] with root cause org.hibernate.PersistentObjectException: detached entity passed to persist: com.reservation.service.domain.Product at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:141)

Answer 1

I had the same problem and solved it by removing the cascade = CascadeType.PERSIST.

In your case you use CascadeType.ALL, which is equivalent to also using the PERSIST, according to the documentation:

Defines the set of cascadable operations that are propagated to the associated entity. The value cascade=ALL is equivalent to cascade={PERSIST, MERGE, REMOVE, REFRESH, DETACH}.

It means when you try to save the reservation on reservationDAO.save(reservation) it will also try to persist the associated Product object. But this object is not attached to this session. So the error occur.

Answer 2

The exception comes as hibernate trying to persist associated products when you save reservation. Persisting the products is only success if they have no id because id of Product is annotated

@GeneratedValue(strategy=GenerationType.AUTO) 

But you got products from repository and ids are not null.

There 2 options to resolve your issue:

1. remove (cascade = CascadeType.ALL) on products of Reservation
2. or remove @GeneratedValue(strategy=GenerationType.AUTO) on id of Product