Hey guys in this post we will discuss and implement Pagination in Data JPA with examples.
Table of Contents
Overview
Pagination is often helpful when we have a large dataset and we want to present it to the user in smaller chunks. Data JPA provides pagination support out of the box. Rather than fetching all the records from the database, we can fetch the records on pages with a specific size.
To add paging support to our Repositories, we need to extend the PagingAndSortingRepository<T, ID> interface rather than the basic CrudRepository<T, ID> interface.
By extending the repository PagingAndSortingRepository<T, ID>, we get the following method –
Page<Laptop> findAll(Pageable pageable);
Returns a Page of entities meeting the paging restriction provided in the Pageable object.
Even we can use JPARepository<T, ID> instead, which extends the PagingAndSortingRepository<T, ID>
Once we extend the repository, we just need to create the object PageRequest object which is the implementation class of the Pageable interface. PageRequest provides the following static method –
Pageable pages = PageRequest.of(pageNumber, pageSize);
we can pass the page number and page size as parameters to the of() method. here the page number starts from 0 indexes.
Once we have our PageRequest object, now we can pass it to the repository methods.
Usage of Interfaces, Classes, and Methods
PagingAndSortingRepository<T, ID>: Extension ofCrudRepositoryto provide additional methods to retrieve entities using the pagination and sorting abstraction.Pageable: Abstract interface for pagination information.Page: A page is a sublist of a list of objects. It allows gain information about the position of it in the containing entire list.PageRequest: Basic Java Bean implementation ofPageable.of(): Creates a new unsortedPageRequest.
Complete example
Let’s create a step-by-step spring boot project and create different finder methods for various fields.
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
);
INSERT INTO tbl_laptops(name, description, brand, price)
VALUES("Dell Inspiron", "dell company laptop", "Dell", 60000.00);
INSERT INTO tbl_laptops(name, description, brand, price)
VALUES("Dell XPS", "dell company laptop", "Dell", 70000.00);
INSERT INTO tbl_laptops(name, description, brand, price)
VALUES("Macbook Air", "apple company laptop", "Apple", 85000.00);
INSERT INTO tbl_laptops(name, description, brand, price)
VALUES("Macbook Pro", "apple company laptop", "Apple", 160000.00);
INSERT INTO tbl_laptops(name, description, brand, price)
VALUES("HP", "hp company laptop", "HP", 50000.00);
INSERT INTO tbl_laptops(name, description, brand, price)
VALUES("Lenovo", "lenovo company laptop", "Lenovo", 50000.00);
SELECT * FROM tbl_laptops;
We have created a table tbl_laptops that contains 5 fields. We have inserted the sample data as well.
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()
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 javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import lombok.Data;
@Entity
@Data
@Table(name="tbl_laptops")
public class Laptop {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;
private String name;
private String description;
private String brand;
private BigDecimal price;
}
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.repos;
import java.math.BigDecimal;
import java.util.List;
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> {
}
@Repository annotates classes at the persistence layer, which will act as a database repository. We have extended this interface with JPARepository interface which will provide built-in methods to interact with the database also we can define finder methods. It also extends the PagingAndSortingRepository<T, ID> repository.
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.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import in.bushansirgur.springboot.entity.Laptop;
import in.bushansirgur.springboot.repos.LaptopRepository;
@RestController
public class LaptopController {
@Autowired
LaptopRepository lRepo;
@GetMapping("/laptops")
public List<Laptop> getAll (@RequestParam Integer page, @RequestParam Integer size) {
Pageable pages = PageRequest.of(page, size);
return lRepo.findAll(pages).toList();
}
}
Here we created the handler method getAll() which will receive two parameters page and size from URL using @RequestParam annotation. Next, we will call the static method of() from PageRequest class which will return the Pageable. Next, we will pass the pageable object to the repository method findAll() which will return Page<Laptop>, we will convert it into a list using toList() method.
Run the app
Run the application using the below maven command –
mvn spring-boot:runOpen the browser and enter the following URL –
http://localhost:8080/laptops?page=0&size=2
[
{
"id": 1,
"name": "Dell Inspiron",
"description": "dell company laptop",
"brand": "Dell",
"price": 60000.0
},
{
"id": 2,
"name": "Dell XPS",
"description": "dell company laptop",
"brand": "Dell",
"price": 70000.0
}
]
http://localhost:8080/laptops?page=1&size=2
[
{
"id": 3,
"name": "Macbook Air",
"description": "apple company laptop",
"brand": "Apple",
"price": 85000.0
},
{
"id": 4,
"name": "Macbook Pro",
"description": "apple company laptop",
"brand": "Apple",
"price": 160000.0
}
]
http://localhost:8080/laptops?page=2&size=2
[
{
"id": 5,
"name": "HP",
"description": "hp company laptop",
"brand": "HP",
"price": 50000.0
},
{
"id": 6,
"name": "Lenovo",
"description": "lenovo company laptop",
"brand": "Lenovo",
"price": 50000.0
}
]
