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Hey guys in this post, we will discuss writing Data JPA JPQL delete query 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 know about writing a JPQL delete query.

Complete example

Let’s create a step-by-step spring boot project and create a JPQL select query. We will write a JPQL query to delete a record by its name.

Create database and insert sample data

Open MySQL workbench and execute the following commands

CREATE DATABASE mydb;

USE mydb;

CREATE TABLE tbl_laptops(
    id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(255) NOT NULL,
    description VARCHAR(255) NOT NULL,
    brand VARCHAR(255) NOT NULL,
    price DOUBLE(10, 2) NOT NULL,
    created_at DATE NOT NULL
);

INSERT INTO tbl_laptops(name, description, brand, price, created_at)
VALUES("Dell Inspiron", "dell company laptop", "Dell", 60000.00, '2021-02-10');
INSERT INTO tbl_laptops(name, description, brand, price, created_at)
VALUES("Dell XPS", "dell company laptop", "Dell", 70000.00, '2020-12-31');
INSERT INTO tbl_laptops(name, description, brand, price, created_at)
VALUES("Macbook Air", "apple company laptop", "Apple", 85000.00, '2021-01-31');
INSERT INTO tbl_laptops(name, description, brand, price, created_at)
VALUES("Macbook Pro", "apple company laptop", "Apple", 160000.00, '2021-12-25');
INSERT INTO tbl_laptops(name, description, brand, price, created_at)
VALUES("HP", "hp company laptop", "HP", 50000.00, '2021-02-10');
INSERT INTO tbl_laptops(name, description, brand, price, created_at)
VALUES("Lenovo", "lenovo company laptop", "Lenovo", 50000.00, '2020-11-21');

SELECT * FROM tbl_laptops;

We have created a table tbl_laptops that contains 5 fields. We have inserted the sample data as well.

Read More:

1. Check this how to write JPQL select query
2. Check this how to write a JPQL update 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 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.sql.Date;

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

import lombok.Data;

@Entity
@Table(name="tbl_laptops")
@Data
public class Laptop {
	
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Long id;
	
	private String name;
	
	private String brand;
	
	private String description;
	
	private BigDecimal price;
	
	@Column(name="created_at")
	private Date createdAt;
}

We have added @Data annotation which is a Lombok annotation, that will automatically create setters, getters, toString(), and equals() for us.

@Entity is a mandatory annotation that indicates that this class is a JPA entity and is mapped with a database table.

@Table annotation is an optional annotation that contains the table info like table name.

@Id annotation is a mandatory annotation that marks a field as the primary key

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.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import in.bushansirgur.springboot.entity.Laptop;

@Repository
public interface LaptopRepository extends JpaRepository<Laptop, Long>{
	
	@Transactional
	@Modifying
	@Query("DELETE FROM Laptop WHERE name = :name")
	Integer deleteByName(String name);
}

• @Query annotation is used to write the JPQL query. JPQL queries take field names instead of column names
• @Modifying annotation is used whenever we writing JPQL query for modifying the records (create, update, delete)
• JPQL query always returns either void or integer whenever we are writing a query for modifying.
• @Transactional annotation is used whenever we are writing JPQL queries, it is from the org.springframework.transaction.annotation.Transactional package

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 org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import in.bushansirgur.springboot.repository.LaptopRepository;

@RestController
public class LaptopController {
	
	@Autowired
	private LaptopRepository lRepo;
	
	@DeleteMapping("/laptops/delete/{name}")
	public ResponseEntity<String> deleteByName(@PathVariable String name) {
		return new ResponseEntity<String>(lRepo.deleteByName(name)+" record(s) deleted", HttpStatus.OK);
	}
}

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/laptops/delete/macbook air

That’s it for this post. Hope you liked it, if so share this with your friends and colleagues, and don’t forget to share this with your social media. Thanks, i will see you in the next post.