JPA Repository Find By List of Ids

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In the JPA Repository, if we need to fetch records based on the find by list of ids from the database table, we can use the findAllById query method. This findAllById is a ready-made method provided by Spring Data JPA to select the records by passing a list of ids. In this topic, we will learn how to implement JPA Repository find by list of ids using Spring Boot, Maven, Spring Web, Lombok, Spring Data JPA and H2 database. 

jpa_repository_find_by_list_of_ids

JPA Repository findAllById method

List<T> findAllById(Iterable<ID> ids)
  • This method returns all instances of the type T with the provided IDs.
  • If in case some or all ids are not found, no entities are returned for these provided IDs.
  • The order of elements in the result is not guaranteed by this method.
  • The CrudRepository interface of Spring Data JPA specifies this method.
  • The parameter ids must not be null nor contain any null values.
  • The method returns guaranteed to be not null. A size can be equal to or less than the number of given ids.
  • This method throws IllegalArgumentException if the given ids or one of its items is null.

Let’s create a restful web service Spring Boot application to fetch a list of employees by the list of ids using the JPA Repository query method findAllById(-) step-by-step.

These are the following steps:

  1. Creating a Spring Boot Starter Project
  2. Keep the IDE ready
  3. Maven Dependency
  4. Defining the configuration
  5. Creating a JPA Entity
  6. Creating a JPA Repository
  7. Creating a Service Interface
  8. Creating a Service class
  9. Creating a Rest Controller class
  10. Run the Spring Application and Check

1. Creating a Spring Boot Starter Project

 We are creating a Spring Boot Application from the web tool Spring Initializr or you can create it from the IDE(STS, VS Code etc.) you are using. 

Add the following dependencies: 

  • Spring Web
  • Spring Data JPA
  • Lombok
  • H2 Database

2. Keep the IDE ready

We are importing this created application into our Eclipse IDE or you can import it into another IDE you are using. You can refer to this article to create and set up the Spring Boot Project in Eclipse IDE.

Project Structure of Find By List of Ids

jpa_repository_find_by_list_of_ids

3. Maven Dependency

Here is the complete pom.xml file for the Spring Boot Application.

pom.xml

<?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>2.6.3</version>
		<relativePath />
		<!-- lookup parent from repository -->
	</parent>
	<groupId>com.springjava</groupId>
	<artifactId>demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>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.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
			<scope>runtime</scope>
		</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>
			</plugin>
		</plugins>
	</build>
</project>

4. Defining the configuration

We are configuring the H2 database configuration in the application.properties file.

application.properties

# H2 Database Configuration
spring.datasource.url=jdbc:h2:mem:test
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.H2Dialect
spring.jpa.hibernate.ddl-auto=update
spring.h2.console.enabled=true

5. Creating a JPA Entity

We are creating a JPA entity class Employee with these properties(id, firstName,lastName, email and department).

Employee.java

package com.springjava.entity;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import lombok.Data;

@Data

@Entity

public class Employee {

  @Id

  @GeneratedValue(strategy = GenerationType.IDENTITY)

  private Long id;

  private String firstName;

  private String lastName;

  private String email;

  private String department;

}
  • This @Data annotation is used for a constructor, setter method, getter method, etc.
  • This @Entity annotation is used to create a table through Java code in the database.

6. Creating a JPA Repository

We are a JPA Repository to interacts with the JPA Entity class and use its query methods(save() and findAllById()).

EmplRepository.java

package com.springjava.repository;

import org.springframework.data.jpa.repository.JpaRepository;

import com.springjava.entity.Employee;

public interface EmplRepository extends JpaRepository < Employee, Long > {

}

7. Creating a Service Interface

 We are creating a Service interface with some method declaration(save(Employee employee) and getByListOfIds(List<Long> ids)). So the implementation class of this interface overrides these declared methods in there.

EmployeeService.java

package com.springjava.service;

import java.util.List;

import com.springjava.entity.Employee;

public interface EmployeeService {

  void save(Employee employee);

  List < Employee > getByListOfIds(List < Long > ids);

}

8. Creating a Service class

We are creating a Service class EmployeeServiceImpl and this class is implementing the EmployeeService interface. This class is annotated with @Service annotation to act service. 

EmployeeServiceImpl.java

package com.springjava.service;

import java.util.List;

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

import org.springframework.stereotype.Service;

import com.springjava.entity.Employee;

import com.springjava.repository.EmplRepository;

@Service

public class EmployeeServiceImpl implements EmployeeService {

  @Autowired

  EmplRepository empRepo;

  @Override

  public void save(Employee employee) {

    empRepo.save(employee);

  }

  @Override

  public List < Employee > getByListOfIds(List < Long > ids) {

    return empRepo.findAllById(ids);

  }

}
  • We used @Autowired annotation to inject the EmplRepository in this service class.
  • We used save() and findAllById() query methods of that JPA Repository.

9. Creating a Rest Controller class

We are creating a RestController class EmployeeController in which all methods are created for API endpoints for handling requests from the clients. 

EmployeeController.Java

package com.springjava.controller;

import java.util.Arrays;

import java.util.LinkedHashMap;

import java.util.List;

import java.util.Map;

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.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

import com.springjava.entity.Employee;

import com.springjava.service.EmployeeService;

@RestController

@RequestMapping("/api/employee")

public class EmployeeController {

  @Autowired

  EmployeeService empService;

  @PostMapping("/save")

  public ResponseEntity < ? > save(@RequestBody Employee employee) {

    Map < String, Object > respEmp = new LinkedHashMap < String, Object > ();

    empService.save(employee);

    respEmp.put("status", 1);

    respEmp.put("message", "Record is Saved Successfully!");

    return new ResponseEntity < > (respEmp, HttpStatus.CREATED);

  }

  @GetMapping("/find-by-list-of-ids")

  public ResponseEntity < ? > getByListOfIds() {

    Map < String, Object > respEmp = new LinkedHashMap < String, Object > ();

    List < Long > ids = Arrays.asList(1 L, 2 L);

    List < Employee > emList = empService.getByListOfIds(ids);

    if (!emList.isEmpty()) {

      respEmp.put("status", 1);

      respEmp.put("data", emList);

      return new ResponseEntity < > (respEmp, HttpStatus.OK);

    } else {

      respEmp.clear();

      respEmp.put("status", 0);

      respEmp.put("message", "Data is not found");

      return new ResponseEntity < > (respEmp, HttpStatus.NOT_FOUND);

    }

  }

}
  • This class is annotated with @RestController annotation to make this class act as Rest Controller for giving responses in JSON form.
  • We used @RequestMapping annotation to define the base URL for the application.
  • We used @PostMapping and @GetMapping annotations to handle HTTP requests from the client.
  • We used ResponseEntity to represent the entire HTTP response.
  • We used @Autowired  annotation to inject EmployeeService into the class.
  • We used @RequestBody annotation to take JSON object in the save() method as the parameter of the Employee class.
  • We have created two restful web services handling methods(save() and getByListOfIds()).
  • save(): This saves Employee records into the database.
  • getByListOfIds(): This fetches a list of Employee records by passing the list of ids as a parameter.

10. Run the Spring Boot Application and Check

Right-click this Spring Boot application on the DemoApplication.java, then click RunAs and select Java Application. 

Check H2 Database

Check the H2 database console and browse this URL “http://localhost:8080/h2-console”.

jpa_repository_find_by_list_of_ids

See the below table here:

jpa_repository_find_by_list_of_ids

Testing API on the Postman

Saving the employee data

POST: http://localhost:8080/api/employee/save

jpa_repository_find_by_list_of_ids

Check the table:

jpa_repository_find_by_list_of_ids

Retrieving the employees by the list of Ids 

GET: http://localhost:8080/api/employee/find-by-list-of-ids 

jpa_repository_find_by_list_of_ids

After this API hit Spring Data JPA (internally uses Hibernate as a JPA provider) generated SQL statement in the console below here:

Hibernate: 
select employee0_.id as id1_0_, 
employee0_.department as departme2_0_, 
employee0_.email as email3_0_,
employee0_.name as name4_0_ 
from 
employee employee0_ 
where 
employee0_.id in (? , ?)

Conclusion

In this topic, we learned how to use the JPA Repository findAllById method in the Spring Boot Restful web services application.

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