Master JPA using Hibernate as the implementation. Learn the basics of JPA - entities, relationships, entity manager, annotations, JPQL and Criteria API. Take a step into the advanced world of JPA - caching, performance tuning(n + 1 queries), mapping inheritance hierarchies. Get a peek into the magic of Spring Data JPA & Spring Data Rest.
package com.ayush.jpa.JpaDemo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class JpaDemoApplication implements CommandLineRunner {
private Logger logger = LoggerFactory.getLogger(JpaDemoApplication.class);
@Autowired
private PersonRepository repo;
public static void main(String[] args) {
SpringApplication.run(JpaDemoApplication.class, args);
}
@Override
public void run(String... args) throws Exception {
// TODO Auto-generated method stub
logger.info("Person findById----", repo.findById(10002));
}
}
package com.ayush.jpa.JpaDemo;
import java.util.Date;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@entity
public class Person {
@Id
@GeneratedValue
private int id;
private String name;
private String location;
private Date birthDate;
public Person() {
}
public Person(int id, String name, String location, Date birthDate) {
super();
this.id = id;
this.name = name;
this.location = location;
this.birthDate = birthDate;
}
public Person(String name, String location, Date birthDate) {
super();
this.name = name;
this.location = location;
this.birthDate = birthDate;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public Date getBirthDate() {
return birthDate;
}
public void setBirthDate(Date birthDate) {
this.birthDate = birthDate;
}
@Override
public String toString() {
return String.format("\nPerson [id=%s, name=%s, location=%s, birthDate=%s]", id, name, location, birthDate);
}
}
package com.ayush.jpa.JpaDemo;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.transaction.Transactional;
import org.springframework.stereotype.Repository;
@repository
@transactional
public class PersonRepository {
@PersistenceContext
EntityManager manager;
public Person findById(int id) {
return manager.find(Person.class, id);
}
}
Hello Ranga,
I am learning the course associated with this repo and I am at the Step#12 of Chapter#5, which is to play with the entitymanager.
This is the target method in my CourseRepository class:
public Long checkDetach() {
Course course = new Course("HAPPY PYTHON");
em.persist(course);
em.flush();
em.detach(course);
course.setName("HAPPY MORE PYTHON");
return course.getId();
}And this is the test method I wrote for the above method:
@Test
@DirtiesContext
public void testCheckDetach() {
// Case will fail in unit testing.
Long newId = courseRepository.checkPersistence();
Course course = courseRepository.findById(newId);
assertEquals("HAPPY PYTHON", course.getName());
}The above test case will not pass as the target course entity is still updated even after it was detached.
However, if running the application directly with the below method defined in the run method as follows:
@Override
public void run(String... args) throws Exception {
courseRepository.checkDetach();
}This will correctly reflect what the checkDetach() specifies, which will successfully detach the target course entity and will not update the associated entry in the h2 database.
So I am quite confused and wondering what I missed to create a correct unit test case for the checkDetach method and I would really appreciate if you could provide some suggestions on that.
Getting the following error while creating new maven project with dependencies jdbc, jpa, h2 and web using spring initializer,
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaMappingContext': Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: At least one JPA metamodel must be present!
Dear Ranga, classmates and friends:
Here my transcription ordered for the Course Agenda, I hope you will like and having useful:
Will employers distinguish between experience working with the native Hibernate API vs. the JPA version of Hibernate when they look at one's resume? I'm going to learn Hibernate soon and I'm thinking I'll just use the JPA interface ... but I don't want to limit myself if its going to make me less marketable.
Thanks for your fantastic courses
Thanks for your support. I have an issue with the application, this Application is not closing automatically to close it i have to press CTRL + C
is there any technique that can close this automatically after completion of whole process.
After pressing CTRL + C logger result is:
Thread-3] ConfigServletWebServerApplicationContext : Closing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@1517365b: startup date [Tue Mar 26 12:19:51 IST 2019]; root of context hierarchy
Please help he in resolving this problem
Hello,
This is not an issue with any of the lectures I simply misunderstood something and need some help. The way I understand @transactional is that it keeps the session (Hibernate) or persistence context (JPA) open and every database change in the method is under one transaction. Also if transactional is not placed on a method, a new persistence context will be created and destroyed for each line of code that accesses entity manager. I wanted to test that this understanding was correct so I took the retrievePassportAndAssociatedStudent test method and removed @transactional. You stated in the course that because fetch type is lazy, the persistence context closes after we call em.find() and therefore the following call to passport.getStudents() should cause a "could not initialize proxy" exception. Well after removing @transactional my code still tested fine with no exceptions and I really cannot understand why. I ensured fetch type is lazy both sides of relationship.
@Test
// @Transactional
public void retrievePassportAndAssociatedStudent() {
Passport passport = em.find(Passport.class, 40001L);
logger.info("Passport -> {}", passport);
logger.info("Passport Student-> {}", passport.getStudent());
}
I have a data model wherein classA has a one-to-many relationship with classB.
When I query classA by ID, I want to limit the classB results in the response.
e.g. lets say classA is a Customer class and classB is an Order class and I want to pull only last 6 (configurable) orders or so instead of lets say the whole history of last 5 years, or whatever is stored.
Right now I get the whole list.
If FullTimeEmployee and PartTimeEmployee classes is declared with @entity then why tables not created in DB
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
An Open Source Machine Learning Framework for Everyone
Django
The Web framework for perfectionists with deadlines.
Laravel
A PHP framework for web artisans
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
Some thing interesting about web. New door for the world.
A server is a program made to process requests and deliver data to clients.
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
Some thing interesting about visualization, use data art
Some thing interesting about game, make everyone happy.
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
Microsoft
Open source projects and samples from Microsoft.
Google
Google ❤️ Open Source for everyone.
Alibaba
Alibaba Open Source for everyone
D3
Data-Driven Documents codes.
Tencent
China tencent open source team.