Hey guys in this post, we will discuss the Data JPA finder method In
examples
Table of Contents
Overview
JPA finder methods are the most powerful methods, we can create finder methods to select the records from the database without writing SQL queries. Behind the scenes, Data JPA will create SQL queries based on the finder method and execute the query for us.
To create finder methods in Data JPA, we need to follow a certain naming convention. To create finder methods for the entity class field name, we need to create a method starting with findBy
followed by field name. We can also write in queries by using In
keyword on the field names
public class Employee {
private String name;
private String location;
//setters and getters
}
To query the database that the employee name contains the given text –
findByNameIn(List<String> names)
To query the database that the employee location contains the given text –
findByLocationIn(List<String> locations)
Behind the scenes, Data JPA will create a SQL query like this –
SELECT * FROM employee WHERE name IN ('Shankar', 'Ramesh');
SELECT * FROM employee WHERE location IN ('India', 'Australia');
As you can see, it’s so much easy to select the records with the help of finder methods. That’s the beauty of Data JPA.
Watch the video
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> {
List<Laptop> findByNameIn(List<String> names);
List<Laptop> findByPriceIn(List<BigDecimal> prices);
}
@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. We have defined 2 finder methods findByNameIn()
and findByPriceIn()
which will return the List<Laptops>
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.math.BigDecimal;
import java.util.Arrays;
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.RestController;
import in.bushansirgur.springboot.entity.Laptop;
import in.bushansirgur.springboot.repos.LaptopRepository;
@RestController
public class LaptopController {
@Autowired
LaptopRepository lRepo;
@GetMapping("/laptops/namein")
public ResponseEntity<List<Laptop>> getLaptopsByNameIn() {
return new ResponseEntity<List<Laptop>>(lRepo.findByNameIn(Arrays.asList("hp", "lenovo")), HttpStatus.OK);
}
@GetMapping("/laptops/pricein")
public ResponseEntity<List<Laptop>> getLaptopsByPriceIn() {
return new ResponseEntity<List<Laptop>>(
lRepo.findByPriceIn(Arrays.asList(new BigDecimal(50000.00), new BigDecimal(85000.00))), HttpStatus.OK);
}
}
We have auto wired the LaptopRepository
using @Autowired
annotation. We have created 2 handler methods, getLaptopsByNameIn()
and getLaptopsByPriceIn()
which will call the repository methods findByNameIn()
and findByPriceIn()
.
Run the app
Run the application using the below maven command –
mvn spring-boot:run
Open the browser and enter the following URL –
http://localhost:8080/laptops/namein
[
{
"id": 5,
"name": "HP",
"brand": "HP",
"description": "hp company laptop",
"price": 50000.0
},
{
"id": 6,
"name": "Lenovo",
"brand": "Lenovo",
"description": "lenovo company laptop",
"price": 50000.0
}
]
http://localhost:8080/laptops/pricein
[
{
"id": 3,
"name": "Macbook Air",
"brand": "Apple",
"description": "apple company laptop",
"price": 85000.0
},
{
"id": 5,
"name": "HP",
"brand": "HP",
"description": "hp company laptop",
"price": 50000.0
},
{
"id": 6,
"name": "Lenovo",
"brand": "Lenovo",
"description": "lenovo company laptop",
"price": 50000.0
}
]