Spring Data Jpa Web support

So far in order to fetch data from underlying data base using Spring Data Jpa, we have Repository intreface which have all the required methods to perform operations on data. required method of Repository interface will be called in controller class.

But this is boilerplate code, in order to remove these redundend code, Spring Data Jpa provides Web support. Web Support enables the controller to perform certain Repositoy interface methods in controller class without even calling the repository interface.

drop database if exists AppleDb;
create database AppleDb;
use AppleDb;
create TABLE apple ( apple_id BIGINT NOT NULL, apple_name VARCHAR(255) DEFAULT NULL,rating int(1) DEFAULT NULL, PRIMARY KEY (apple_id)) ENGINE=INNODB;
create TABLE hibernate_sequence ( next_val BIGINT) ENGINE=INNODB;

insert into hibernate_sequence values ( 1 );
insert into apple (apple_name, apple_id, taste) values ("Macintosh", 1, "tangy");
insert into apple (apple_name, apple_id, taste) values ("Fuji", 2, "sweet");
insert into apple (apple_name, apple_id, taste) values ("Gala", 3, "juicy");
insert into apple (apple_name, apple_id, taste) values ("Jonagold", 4, "firm sweet");
insert into apple (apple_name, apple_id, taste) values ("GrannySmith", 5, "sharp");

package com.sujan.example.jpa.controller;

import com.sujan.example.jpa.entity.Apple;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AppleController {

    @GetMapping("/{appleId}")
    public Apple findAppleById(@PathVariable("appleId") Apple apple) {
        return apple;
    }
}

package com.sujan.example.jpa.entity;

import lombok.Data;
import lombok.NoArgsConstructor;

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

@Data
@Entity
@NoArgsConstructor
public class Apple {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long appleId;
    private String appleName;
    private int rating;
}

package com.sujan.example.jpa.repository;

import com.sujan.example.jpa.entity.Apple;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface AppleRepository extends JpaRepository<Apple, Long> {
}

package com.sujan.example.jpa;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class JpaApplication {
    public static void main(String[] args) {
        SpringApplication.run(JpaApplication.class, args);
    }
}

spring.datasource.url=jdbc:mysql://localhost:3306/AppleDb
spring.datasource.username=root
spring.datasource.password=root

plugins {
    id 'org.springframework.boot' version '2.3.3.RELEASE'
    id 'io.spring.dependency-management' version '1.0.10.RELEASE'
    id 'java'
}
group = 'com.sujan'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'
configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}
repositories {
    mavenCentral()
}
dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    annotationProcessor 'org.projectlombok:lombok'
    compileOnly 'org.projectlombok:lombok'
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    runtimeOnly 'mysql:mysql-connector-java'
    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }
}
test {
    useJUnitPlatform()
}

curl --location --request GET 'http://localhost:8080/1'

select apple0_.apple_id as apple_id1_0_0_, apple0_.apple_name as apple_na2_0_0_, apple0_.taste as taste3_0_0_ from apple apple0_ where apple0_.apple_id=?

it might be tempting to pass Apple entity while calling because findAppleById methods takes Apple entity as RequestBody, but its not required.

Spring Data Jpa internally uses DomainClassConverter class to convert the Path Variable appleId into the Apple domain class's appleId and uses it for finding the record with given appleId from Repository interface. hence we dont need to manyally search or write code for it.

Spring Data Jpa Web support

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