Spring Boot with Spring Data JPA

Question

Environment :

Spring boot 1.4.0.RELEASE

Code :

I have a simple Spring REST web service set up as below :

Spring Data JPA Dao Layer:

public interface UserDao extends JpaRepository<User,Long>{

}

Spring Service Layer :

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    private UserDao userDao;

    @Override
    public void saveUser(User user){        
        userDao.save(user);     
    }
}

Spring Controller :

@RestController
public class UserController {

    @Autowired
    private UserService userService; 


    @RequestMapping(value = "/user", method = RequestMethod.POST)
    @ResponseStatus(HttpStatus.CREATED)
    public void saveUser(@RequestBody User user){

        this.userService.saveUser(user);
    }
}

pom.xml extract :

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <scope>provided</scope>
    </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>


        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

Issue/Queries :

With above set up when I call UserController.saveUser , everything works fine and data gets saved to DB. I am using in memory H2 db .

So my questions are :

1)My service layer is NOT MARKED WITH @Transactional nor I am using any AOP config ?
So who is creating/managing transaction here ?

After debugging the application , it seems that Spring Data JPA Repository class has AOPProxy CGLIB semantics ? That means this class is running inside transaction . Is this the default behaviour if we don't make Spring Service as @Transactional ?

2)When Spring Boot is used , all of the below things are configured automatically for you based on classpath :

1)DataSource

2)Transaction Manager

If this is the case , I have seen a couple of tutorials where persistence config contains below : Why is this required then ? Should Spring boot not configure all of the below things automatically for you ?

   @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        final LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource());
        em.setPackagesToScan(new String[] { "com.atul.domain" });
        final HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        em.setJpaProperties(additionalProperties());
        return em;
    }

    @Bean
    public DataSource dataSource() {
        final DriverManagerDataSource dataSource = new DriverManagerDataSource();
        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;
    }

    @Bean
    public JpaTransactionManager transactionManager() {
        final JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(entityManagerFactory().getObject());
        return transactionManager;
    }

Answer 1

1) Spring Data creates a transaction around calls to repository methods by default (see http://docs.spring.io/spring-data/jpa/docs/current/reference/html/#transactions). So, if your service layer is not marked with @Transactional, each repository call will have its own transaction by default (which is undesirable in many situations).

2) This extra configuration code is only needed if the default does not suffice for your needs. In your code example, I see nothing that you cannot configure with Spring Boot features, so this extra code is not really needed.