Enabling exception translation for JPA in plain Spring

I was setting up a basic CRUD web app with JPA in plain Spring (no Spring Boot or Spring Data JPA) for educational purposes and faced a strange problem: Spring doesn’t translate exceptions for my repository. According to the Spring documentation (here and here), it is sufficient to mark the repository with the @Repository annotation and Spring will automatically enable exception translation for this repository.

However, when I did so and triggered a UNIQUE constraint violation, I still was getting a JPA PersistenceException (with a Hibernate ConstraintViolationException inside) instead of the Spring DataIntegrityViolationException.

I used pure Java Spring configuration and it took me quite some time to realize that I should compare it with the XML configuration in the documentation. Compared to the pure Java configuration, the XML configuration adds a PersistenceExceptionTranslationPostProcessor into the context. When I added it manually with @Bean, it worked, but now I have a question.

Have I misconfigured something? The Spring documentation doesn’t require registering that post-processor manually for pure Java configuration. Maybe there is another way to register it, say an @EnableXXX annotation?

Here is the summary of my configuration.

@Configuration
@ComponentScan("com.example.secured_crm")
public class SpringConfiguration {
    // the problem is solved if I uncomment this
    //@Bean
    //public PersistenceExceptionTranslationPostProcessor exceptionTranslation() {
    //    return new PersistenceExceptionTranslationPostProcessor();
    //}
}

@Configuration
@PropertySource("classpath:db.properties")
@EnableTransactionManagement
public class DataSourceConfiguration {

    @Value("${jdbc.driver}")
    private String driverClass;

    @Value("${jdbc.url}")
    private String url;

    // ...

    @Value("${hibernate.debug}")
    private String hibernateDebug;

    @Bean
    public DataSource dataSource() {
        var dataSource = new ComboPooledDataSource();
        // ...
        return dataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        var emFactory = new LocalContainerEntityManagerFactoryBean();
        emFactory.setDataSource(dataSource());
        emFactory.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        emFactory.setPackagesToScan("com.example.secured_crm.entities");
        var properties = new Properties();
        properties.setProperty("hibernate.dialect", hibernateDialect);
        properties.setProperty("hibernate.show_sql", hibernateDebug);
        properties.setProperty("hibernate.format_sql", "true");
        emFactory.setJpaProperties(properties);
        return emFactory;
    }

    @Bean
    public PlatformTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {
        var txManager = new JpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory);
        return txManager;
    }
}

public interface UserRepository {
    User findByName(String username);
    List<User> findAll();
    void save(User user);
    boolean deleteById(int id);
    User findById(int id);
}

@Repository
public class UserJpaRepository implements UserRepository {
    @PersistenceContext
    EntityManager em;

    @Override
    public void save(User user) {
        if (user.getId() == null) {
            em.persist(user);
        } else {
            em.merge(user);
        }
    }

   // and so on...
}

By the way, when I tried to add the post-processor in DataSourceConfiguration, it disabled @PropertySource effect. So far my impression of Spring is that it’s one big hack…

>Solution :

It requires to manually register PersistenceExceptionTranslationPostProcessor in order for the exception translation to take effect.

The documentation you mentioned simply does not updated yet to show a fully working java configuration. It should mention to register this post processor. ( So feel free to provide a PR to update the docs.).

If you check from its javadoc , it already mentioned PersistenceExceptionTranslationPostProcessor is necessary to be registered :

As a consequence, all that is usually needed to enable automatic
exception translation is marking all affected beans (such as
Repositories or DAOs) with the @Repository annotation, along with
defining this post-processor as a bean in the application context.

P.S. If you are using spring-boot , and if it detects PersistenceExceptionTranslationPostProcessor is in the class-path , it will automatically register it by default such that you do not need to register manually.