One To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And Oracle

In this tutorial, we will see One to Many Annotation Mapping Example in Hibernate/JPA using Spring Boot and Oracle. We are going to use maven, embedded tomcat, postman and oracle database. Here we will have some rest endpoint which will be used to save and retrieve data in the database.

We have two entity Book.java and Story.java which are mapped in One To Many relationships. In this example, we are assuming one Book can have multiple stories. After running the below example we will be able to save the Book and Story entity which is in One To Many relationships.

Save URL – http://localhost:9091/book/savebook

 

Get URL- http://localhost:9091/book/1

 

Database entry –

 

Let’s see complete example One To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And Oracle from scratch.

Before going ahead, let’s see some points.

• We are going to use two annotations @OneToMany and @JoinColumn for mapping.
• We will not create a table manually, let’s hibernate do this job.

Note –  Default Fetch type in case of the below annotations.

@OneToOne – Default fetch type is EAGER.
@OneToMany – Default fetch type is LAZY.
@ManyToOne – Default fetch type is EAGER.
@ManyToMany – Default fetch type is LAZY.

We will use the spring boot library (will provide dependency in pom.xml) to make sure all necessary jar/library is easily available for our application. Spring boot will take care of all jars. Le’s see One To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And Oracle from scratch.

Prerequisites –

• JDK 1.8
• Oracle 10g
• Eclipse
• maven
• postman

Open eclipse and create maven project, Don’t forget to check ‘Create a simple project (skip)’click on next. Fill all details(GroupId – onetomanyhibernatejpa, ArtifactId – onetomanyhibernatejpa and name – onetomanyhibernatejpa) and click on finish. Keep packaging as the jar.

Modify the pom.xml with the below code.

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>onetoonehibernatejpa</groupId>
	<artifactId>onetoonehibernatejpa</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>onetomanyhibernatejpa</name>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.2.RELEASE</version>
	</parent>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>

		</dependency>

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

		<dependency>
			<groupId>com.oracle</groupId>
			<artifactId>ojdbc6</artifactId>
			<version>11.2.0.3</version>
		</dependency>

	</dependencies>

	<build>
		<finalName>${project.artifactId}</finalName>
		<plugins>

			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.1</version>
				<configuration>
					<fork>true</fork>
					<executable>C:\Program Files\Java\jdk1.8.0_131\bin\javac.exe</executable>
				</configuration>
			</plugin>


		</plugins>
	</build>
</project>

Note – In pom.xml we have defined javac.exe path in configuration tag. You need to change accordingly i.e where you have installed JDK.

If you see any error for oracle dependency then follow these steps.

Let maven download all necessary jar. Once it is done we will able to see the maven dependency folder which contains different jar files.

 

We are good now. We can start writing our controller classes, ServiceImpl and Repository. The directory structure of the application looks as below.

 

 

Define entity class i.e Book.java and Story.java.

Book.java

package com.hibernatejpa.entity;

import java.util.ArrayList;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;

import com.fasterxml.jackson.annotation.JsonManagedReference;

@Entity
public class Book {

	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private int bookId;

	@Column(name = "book_name")
	private String bookName;

	@OneToMany(cascade = CascadeType.ALL, fetch= FetchType.LAZY)
	@JoinColumn(name = "book_id",referencedColumnName="bookId")
	private List<Story> storyList = new ArrayList<>();

	public int getBookId() {
		return bookId;
	}

	public void setBookId(int bookId) {
		this.bookId = bookId;
	}

	public String getBookName() {
		return bookName;
	}

	public void setBookName(String bookName) {
		this.bookName = bookName;
	}

	public List<Story> getStoryList() {
		return storyList;
	}

	public void setStoryList(List<Story> storyList) {
		this.storyList = storyList;
	}
	
	

}

Story.java

package com.hibernatejpa.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Story {

	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private int storyId;

	@Column(name = "story_name")
	private String storyName;

	public int getStoryId() {
		return storyId;
	}

	public void setStoryId(int storyId) {
		this.storyId = storyId;
	}

	public String getStoryName() {
		return storyName;
	}

	public void setStoryName(String storyName) {
		this.storyName = storyName;
	}

}

 

Define the repository interface extending CrudRepository.

BookRepository.java

package com.hibernatejpa.repository;

import java.io.Serializable;

import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;

import com.hibernatejpa.entity.Book;
@Repository
public interface BookRepository extends CrudRepository<Book,Serializable> {
	public Book findByBookId(int bookId);
}

Define service interface i.e BookService.java

package com.hibernatejpa.service;

import org.springframework.stereotype.Component;

import com.hibernatejpa.entity.Book;

@Component
public interface BookService {
	public Book saveBook(Book book);
	public Book findByBookId(int bookId);
}

Define service implementation class.

BookServiceImpl.java

package com.hibernatejpa.impl;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.hibernatejpa.entity.Book;
import com.hibernatejpa.entity.Story;
import com.hibernatejpa.repository.BookRepository;
import com.hibernatejpa.service.BookService;

@Service("bookServiceImpl")
public class BookServiceImpl implements BookService {

	@Autowired
	private BookRepository bookRepository;

	public Book saveBook(Book book) {

		book = bookRepository.save(book);
		return book;

	}

	public Book findByBookId(int bookId) {
		Book book = bookRepository.findByBookId(bookId);
		return book;
	}
}

Note – See here more about @Component, @Controller, @Service and @Repository annotations here.

Define the controller class or endpoint.

BookController.java

package com.hibernatejpa.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import com.hibernatejpa.entity.Book;
import com.hibernatejpa.service.BookService;

@RestController
@RequestMapping(value = "/book")
public class BookController {

	@Autowired
	private BookService bookService;

	@RequestMapping(value = "/savebook", method = RequestMethod.POST)
	@ResponseBody
	public Book saveBook(@RequestBody Book book) {
		Book bookResponse = bookService.saveBook(book);
		return bookResponse;
	}

	@RequestMapping(value = "/{bookId}", method = RequestMethod.GET)
	@ResponseBody
	public Book getBookDetails(@PathVariable int bookId) {
		Book bookResponse = bookService.findByBookId(bookId);

		return bookResponse;
	}

}

Note – See more details about @Controller and RestController here.

Define the JpaConfig.java

package com.hibernatejpa.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@Configuration
@EnableJpaRepositories(basePackages = "com.hibernatejpa.repository")
public class JpaConfig {

}

Step 12 – Define the SpringMain.java

package com.hibernatejpa.main;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@ComponentScan(basePackages="com.hibernatejpa.*")
@EntityScan("com.hibernatejpa.*")
public class SpringMain {
	public static void main(String[] args) {

        SpringApplication.run(SpringMain.class, args);
    }

}

 

And finally, we have an application.properties file where we have database details.

application.properties

# Connection url for the database
spring.datasource.url=jdbc:oracle:thin:@localhost:1521:XE
spring.datasource.username=SYSTEM
spring.datasource.password=oracle2
spring.datasource.driver-class-name=oracle.jdbc.driver.OracleDriver
# Show or not log for each sql query
spring.jpa.show-sql = true
 
 
spring.jpa.hibernate.ddl-auto =create
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.Oracle10gDialect
 
server.port = 9091

We are almost done. Just build the project once running the main method. Open git bash or cmd and Run mvn clean install.

Let’s deploy the application running SpringMain class as a java application.

Now we will prepare json data and will try save in database.

Sample request JSON data-

{
	"bookName": "Premchand's best stories",
	"storyList": [{
			"storyName": "Stories of two oxes"
		},
		{
			"storyName": "idgah"
		},
		{
			"storyName": "Poosh Ki Rat"
		}
	]
}

 

Let’s test the save url.

 

Let’s check the database.

 

Yes, we have data in the book as well as story table. Did you notice in the book table book_id  is a foreign key?

Let’s see in the below diagram which will give us a brief about flow.

 

That’s all about One To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And Oracle.

One to One Mapping Annotation Example in Hibernate/JPA using Spring Boot and Oracle.
One to One Bidirectional Mapping Example In Hibernate/JPA Using Spring Boot and Oracle.
One To Many Bidirectional Mapping In Hibernate/JPA Annotation Example Using Spring Boot and Oracle
Many To One Unidirectional Mapping In Hibernate/JPA Annotation Example Using Spring Boot and Oracle.
Many To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And Oracle.

@OneToMany Docs.

Summary – We have seen One To Many Mapping Annotation Example In Hibernate/JPA Using Spring Boot And Oracle.