Spring Data Jpa Query by Example

Spring Data Jpa Example Matchers

ExampleMatcher interface is provided by Spring Data Jpa to specify settings for String matcher, null handling , and attribute specific settings.

drop database if exists AppleDb;
create database AppleDb;
use AppleDb;
create TABLE apple ( apple_id BIGINT NOT NULL, apple_name VARCHAR(255) DEFAULT NULL, taste VARCHAR(255) 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, '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 com.sujan.example.jpa.repository.AppleRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Example;
import org.springframework.data.domain.ExampleMatcher;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AppleController {
    @Autowired
    private AppleRepository appleRepository;

    @GetMapping
    void queryByExample(@RequestParam("taste") String taste) {
        Apple apple = new Apple();
        apple.setTaste(taste);
        ExampleMatcher matcher = ExampleMatcher.matching()
                .withIgnorePaths("appleName", "appleId")
                .withIncludeNullValues()
                .withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING);
        Example<Apple> example = Example.of(apple, matcher);
        Iterable<Apple> all = appleRepository.findAll(example);
        all.forEach(System.out::println);
    }
}

package com.sujan.example.jpa.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

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

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

package com.sujan.example.jpa.repository;

import com.sujan.example.jpa.entity.Apple;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.repository.query.QueryByExampleExecutor;
import org.springframework.stereotype.Repository;

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

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?autoReconnect=true&useSSL=false&createDatabaseIfNotExist=true
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.show-sql=true
spring.datasource.initialization-mode=always

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/?taste=wee'

select apple0_.apple_id as apple_id1_0_, apple0_.apple_name as apple_na2_0_, apple0_.taste as taste3_0_ from apple apple0_ where apple0_.taste like ? escape ?
Apple(appleId=2, appleName=Fuji, taste=sweet)
Apple(appleId=4, appleName=Jonagold, taste=sweet)