spring boot jpa

Innocent Iguana answered on April 2, 2024 Popularity 10/10 Helpfulness 2/10

answer spring boot jpa

related spring data jpa

spring boot jpa

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/* NOTE: This is Spring JPA and NOT SPRING DATA JPA
* Spring JPA uses EntityManager to handle entity management
* Spring Data JPA uses a layer of abstraction which further simplifies this process
*/

// application.properties
spring.h2.console.enabled=true
spring.datasource.url=jdbc:h2:mem:testdb
spring.jpa.show-sql=true // this will show the sql equivalence of JPA operations behind the scene in console

// Course.java
@Entity(name="Course") // name of the table which this class will be mapped with
public class Course {
	@Id // primary key column
	private long id;
	@Column(name="name") // name of the column that this attribute will be mapped to
	private String name;
	@Column(name="author")
	private String author;

	public Course() {}

	public Course(long id, String name, String author) {
		super();
		this.id = id;
		this.name = name;
		this.author = author;
	}

	// setters
	// getters
	// toString

}

// CourseJpaRepository.java
@Repository
@Transactional
public class CourseJpaRepository {
	
	@PersistenceContext // Alternative to @Autowired
	private EntityManager entityManager; // this will be responsible to manage the operations
	
	public void insert(Course course) {
		entityManager.merge(course); // .merge() is used to insert
	}
	
	public Course findById(long id) {
		return entityManager.find(Course.class, id);
	}

	public void deleteById(long id) { // There is no direct way of deletion. First you need to find the item and remove the object next
		Course course = entityManager.find(Course.class, id);
		entityManager.remove(course);
	}

}

// CourseCommandLineRunner.java that makes sure to run everything on startup
@Component
public class CourseCommandLineRunner implements CommandLineRunner{

	@Autowired
	private CourseJpaRepository repository;
	
	@Override
	public void run(String... args) throws Exception {
		// Insert operations
		repository.insert(new Course(1, "Learn AWS!", "Udemy"));
		repository.insert(new Course(2, "Learn Azure!", "Udemy"));
		repository.insert(new Course(3, "Learn GCP!", "Udemy"));
		// Delete operation
		repository.deleteById(1);
		// Read operations
		System.out.println(repository.findById(2));
		System.out.println(repository.findById(3));
	}
}

Popularity 10/10 Helpfulness 2/10 Language java

Source: Grepper

Tags: java jpa spring-boot

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Contributed on Apr 02 2024

Innocent Iguana

0 Answers Avg Quality 2/10

Closely Related Answers

spring data jpa

Comment

/* NOTE: This is SPRING DATA JPA and NOT SPRING JPA
* While Spring JPA uses EntityManager to handle entity management
* Spring Data JPA uses a layer of abstraction which further simplifies this process
*  It extends JpaRepository that helps to run EntityManager behind simple interface without directly using it
*/

// application.properties
spring.h2.console.enabled=true
spring.datasource.url=jdbc:h2:mem:testdb
spring.jpa.show-sql=true // this will show the sql equivalence of JPA operations behind the scene in console

// Course.java
@Entity(name="Course") // name of the table which this class will be mapped with
public class Course {
	@Id // primary key column
	private long id;
	@Column(name="name") // name of the column that this attribute will be mapped to
	private String name;
	@Column(name="author")
	private String author;

	public Course() {}

	public Course(long id, String name, String author) {
		super();
		this.id = id;
		this.name = name;
		this.author = author;
	}

	// setters
	// getters
	// toString

}

// CourseSpringDataJpaRepository.java
public interface CourseSpringDataJpaRepository extends JpaRepository<Course, Long>{
	
	List<Course> findByAuthor(String author); // custom read method signature, findBy...FieldNameFromEntity
	List<Course> findByName(String name); // custom read method signature, findBy...FieldNameFromEntity

}

// CourseCommandLineRunner.java that makes sure to run everything on startup
@Component
public class CourseCommandLineRunner implements CommandLineRunner{

	@Autowired
	private CourseSpringDataJpaRepository repository;
	
	@Override
	public void run(String... args) throws Exception {
        // Insert operation
		repository.save(new Course(1, "Learn AWS !", "Udemy"));
		repository.save(new Course(2, "Learn Azure !", "Udemy"));
		repository.save(new Course(3, "Learn DevOps !", "Udemy"));
		// Delete operation
		repository.deleteById(1l);
		// Read Operation
		System.out.println(repository.findById(2l)); // 2 long type value
		System.out.println(repository.findAll());
		System.out.println(repository.count());
		// Custom read operations
		System.out.println(repository.findByAuthor("Udemy"));
		System.out.println(repository.findByName("Learn AWS !"));
	}
}

Popularity 10/10 Helpfulness 2/10 Language java

Source: Grepper

Tags: java

Link to this answer
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Contributed on Apr 02 2024

Innocent Iguana

0 Answers Avg Quality 2/10

spring boot jpa

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