Simplify CRUD with Spring Data JPA: From Setup to Unit Tests

In the first article of the data‑access chapter we introduced using JdbcTemplate for basic CRUD operations. Combining it with the web module enables simple backend applications, but repetitive CRUD code quickly becomes cumbersome.

Frameworks like Hibernate map Java entities to database tables, yet developers still need to create many DAO interfaces and implementations.

Spring Data JPA eliminates most of this boilerplate: by extending JpaRepository you obtain full CRUD support without writing any implementation code.

public interface UserRepository extends JpaRepository<User, Long> {
    User findByName(String name);
    User findUser(@Param("name") String name);
}

Configuration steps

Add the Spring Data JPA starter to pom.xml:

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

Configure the datasource and hibernate.hbm2ddl.auto property in application.properties (or application.yml) to control schema creation: create: drop and recreate tables on each startup. create-drop: create tables on startup and drop them on shutdown. update: create missing tables and update schema without losing data. validate: only validate the schema against the entities.

Define an entity class:

@Entity
@Data
@NoArgsConstructor
public class User {
    @Id
    @GeneratedValue
    private Long id;
    private String name;
    private Integer age;
    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
}

Create a repository interface extending JpaRepository:

public interface UserRepository extends JpaRepository<User, Long> {
    User findByName(String name);
    User findByNameAndAge(String name, Integer age);
    @Query("from User u where u.name=:name")
    User findUser(@Param("name") String name);
}

Spring Data JPA derives queries from method names (e.g., findByName, findByNameAndAge) and also supports custom JPQL via @Query.

Unit testing

@RunWith(SpringRunner.class)
@SpringBootTest
public class ApplicationTests {
    @Autowired
    private UserRepository userRepository;
    @Test
    public void test() throws Exception {
        // create 10 records
        userRepository.save(new User("AAA", 10));
        // ... other records omitted for brevity ...
        userRepository.save(new User("JJJ", 100));
        // verify CRUD operations
        Assert.assertEquals(10, userRepository.findAll().size());
        Assert.assertEquals(60, userRepository.findByName("FFF").getAge().longValue());
        // delete and verify
        userRepository.delete(userRepository.findByName("AAA"));
        Assert.assertEquals(9, userRepository.findAll().size());
    }
}

Spring Data JPA is part of the broader Spring Data umbrella, offering similar abstractions for other stores such as Redis, MongoDB, and Elasticsearch.

Source code for the examples is available in the chapter3-4 directory of the GitHub repository https://github.com/dyc87112/SpringBoot-Learning/ and the Gitee mirror.