Spring Boot Crud Example Using One to Many Mapping
Hey guys in this post, we will discuss JPA One-to-Many Uni-directional mapping with Example. We will create a spring boot project step by step and connect it to the MySQL database. Follow this tutorial till the end to understand the JPA one-to-many uni-directional mapping. This is the continuation of the previous post, please follow that post before proceeding with this.
Complete example
Let's create a step-by-step spring boot project and create a bi-directional mapping between the two tables. We will create a mapping between Laptop and Color tables.
Read More:
- Check this how to write JPQL select query
- Check this how to write a JPQL delete query
Create spring boot project
There are many different ways to create a spring boot application, you can follow the below articles to create one –
>> Create spring boot application using Spring initializer
>> Create spring boot application in Spring tool suite [STS]
>> Create spring boot application in IntelliJ IDEA
Add maven dependencies
Open pom.xml and add the following dependencies –
<?xml version="1.0" encoding="UTF-8"?> <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 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.4.4</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>in.bushansirgur</groupId> <artifactId>findbyfieldname</artifactId> <version>v1</version> <name>findbyfieldname</name> <description>Spring boot data jpa find by field name</description> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <scope>runtime</scope> <optional>true</optional> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <optional>true</optional> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <excludes> <exclude> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </exclude> </excludes> </configuration> </plugin> </plugins> </build> </project> spring-boot-starter-web dependency for building web applications using Spring MVC. It uses the tomcat as the default embedded container.
spring-boot-devtools dependency for automatic reloads or live reload of applications. spring-boot-starter-data-jpa dependency is a starter for using Spring Data JPA with Hibernate. lombok dependency is a java library that will reduce the boilerplate code that we usually write inside every entity class like setters, getters, and toString()
Configure the datasource
spring.datasource.url=jdbc:mysql://localhost:3306/mydb spring.datasource.username=scbushan05 spring.datasource.password=scbushan05 spring.jpa.hibernate.ddl-auto=update Create an entity class
Create Color.java inside the in.bushansirgur.springboot.entity package and add the following content
package in.bushansirgur.springboot.entity; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; import lombok.Getter; import lombok.Setter; @Entity @Table(name = "tbl_colors") @Setter @Getter public class Color { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String color; @ManyToOne @JoinColumn(name = "laptop_id") private Laptop laptop; } -
@ManyToOneannotation is used to add one to many relationships between two tables -
@JoinColumnannotation is used to join a new column, this will be the foreign key column of the tbl_laptops table -
@Dataannotation which is a Lombok annotation, that will automatically create setters, getters, toString(), and equals() for us. -
@Entityis a mandatory annotation that indicates that this class is a JPA entity and is mapped with a database table. -
@Tableannotation is an optional annotation that contains the table info like table name.
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@Idannotation is a mandatory annotation that marks a field as the primary key
Create Laptop.java inside the in.bushansirgur.springboot.entity package and add the following content
package in.bushansirgur.springboot.entity; import java.math.BigDecimal; import java.util.List; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.OneToMany; import javax.persistence.Table; import in.bushansirgur.springboot.request.LaptopRequest; import lombok.Getter; import lombok.NoArgsConstructor; import lombok.Setter; @Entity @Table(name="tbl_laptops") @Getter @Setter @NoArgsConstructor public class Laptop { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String name; private String brand; private BigDecimal price; public Laptop(LaptopRequest request) { this.name = request.getName(); this.price = request.getPrice(); this.brand = request.getBrand(); } } Create a Repository
Create an interface LaptopRepository.java inside the in.bushansirgur.springboot.repos package and add the following content
package in.bushansirgur.springboot.repository; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.stereotype.Repository; import in.bushansirgur.springboot.entity.Laptop; @Repository public interface LaptopRepository extends JpaRepository<Laptop, Long>{ } Create an interface ColorRepository.java inside the in.bushansirgur.springboot.repos package and add the following content
package in.bushansirgur.springboot.repository; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.stereotype.Repository; import in.bushansirgur.springboot.entity.Color; @Repository public interface ColorRepository extends JpaRepository<Color, Long> { } Create a Request class
Create a class LaptopRequest.java inside the in.bushansirgur.springboot.request package and add the following content
package in.bushansirgur.springboot.request; import java.math.BigDecimal; import java.util.List; import lombok.Getter; import lombok.Setter; @Setter @Getter public class LaptopRequest { private String name; private String brand; private BigDecimal price; private List<String> colors; } This is just a plain old java object (POJO), contains private fields, setters, and getters. This class is used to send the JSON payload from the client.
Create a Response class
Create a class LaptopResponse.java inside the in.bushansirgur.springboot.response package and add the following content
package in.bushansirgur.springboot.response; import java.math.BigDecimal; import java.util.List; import lombok.Getter; import lombok.Setter; @Getter @Setter public class LaptopResponse { private Long id; private String laptop; private BigDecimal price; private String brand; private List<String> colors; } Create a class ColorResponse.java inside the in.bushansirgur.springboot.response package and add the following content
package in.bushansirgur.springboot.response; import java.math.BigDecimal; import lombok.Getter; import lombok.Setter; @Setter @Getter public class ColorResponse { private Long id; private String laptop; private BigDecimal price; private String brand; private String color; } These are just plain old java objects (POJOs) that contain private fields, setters, and getters. These response classes are used to send the final JSON to the client.
Create a Rest controller
Create LaptopController.java inside the in.bushansirgur.springboot.controller package and add the following content
package in.bushansirgur.springboot.controller; import java.util.ArrayList; import java.util.List; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpStatus; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RestController; import in.bushansirgur.springboot.entity.Color; import in.bushansirgur.springboot.entity.Laptop; import in.bushansirgur.springboot.repository.ColorRepository; import in.bushansirgur.springboot.repository.LaptopRepository; import in.bushansirgur.springboot.request.LaptopRequest; import in.bushansirgur.springboot.response.LaptopResponse; @RestController public class LaptopController { @Autowired private LaptopRepository lRepo; @Autowired private ColorRepository cRepo; @PostMapping("/laptops/save") public ResponseEntity<Laptop> saveData (@RequestBody LaptopRequest req) { Laptop laptop = new Laptop(req); laptop = lRepo.save(laptop); for (String s : req.getColors()) { Color c = new Color(); c.setColor(s); c.setLaptop(laptop); cRepo.save(c); } return new ResponseEntity<>(laptop, HttpStatus.CREATED); } } Create ColorController.java inside the in.bushansirgur.springboot.controller package and add the following content
package in.bushansirgur.springboot.controller; import java.util.ArrayList; import java.util.List; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; import in.bushansirgur.springboot.entity.Color; import in.bushansirgur.springboot.repository.ColorRepository; import in.bushansirgur.springboot.response.ColorResponse; @RestController public class ColorController { @Autowired private ColorRepository cRepo; @GetMapping("/colors") public List<ColorResponse> getColors () { List<Color> list = cRepo.findAll(); List<ColorResponse> responseList = new ArrayList<>(); list.forEach(c -> { ColorResponse response = new ColorResponse(); response.setId(c.getId()); response.setLaptop(c.getLaptop().getName()); response.setBrand(c.getLaptop().getBrand()); response.setPrice(c.getLaptop().getPrice()); response.setColor(c.getColor()); responseList.add(response); }); return responseList; } } Run the app
Run the application using the below maven command –
mvn spring-boot:run Open the browser and enter the following URL –
-
localhost:8080/colors
That's it for this post, I hope you guys enjoyed this post. If you did, please share this post with your friends and colleagues. Also, share this post on your social media profile. Thanks, I will see you in the next post.
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Spring Boot Crud Example Using One to Many Mapping
Source: https://bushansirgur.in/spring-data-jpa-one-to-many-uni-directional-example/
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