Spring Boot with Spring Data JPA

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; }