Spring Boot GraphQL N+1 Problem

An application response has many dependencies or nested objects. by default an application loads the parent object first, then its child objects, which is also known as N+1 problem, which makes the application slow and inefficient. In the below application, for each apple in response, it's dependent vendor is called, ie for each N apple, there will be an N+1 API call to load the vendor. ie 1 call to load the apple and N call to load the vendor. let's see it with an example.

package org.wesome.graphql.controllers;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.graphql.data.method.annotation.QueryMapping;
import org.springframework.graphql.data.method.annotation.SchemaMapping;
import org.springframework.stereotype.Controller;
import org.wesome.graphql.entity.Apple;
import org.wesome.graphql.entity.Vendor;
import org.wesome.graphql.service.AppleService;
import org.wesome.graphql.service.VendorService;

import java.util.List;

@Controller
public class AppleControllerGraphQl {
    @Autowired
    private AppleService appleService;
    @Autowired
    private VendorService vendorService;

    @QueryMapping("apples")
    public List<Apple> apples() {
        System.out.println("AppleControllerGraphQl.apples");
        return appleService.getAll();
    }

    @SchemaMapping
    public List<Vendor> vendors(Apple apple) {
        System.out.println("AppleControllerGraphQl.vendors");
        return this.vendorService.getOneAppleVendor(apple);
    }
}

package org.wesome.graphql.data;

public enum AppleName {
    MACINTOSH("Macintosh"),
    FUJI("Fuji"),
    GALA("Gala"),
    JONAGOLD("Jonagold");
    private String appleName;

    AppleName(String appleName) {
        this.appleName = appleName;
    }
}

package org.wesome.graphql.data;

public enum AppleTaste {
    SWEET("sweet"), TANGY("tangy"), BITTER("bitter"), SOUR("sour");
    private final String appleTaste;

    AppleTaste(String appleTaste) {
        this.appleTaste = appleTaste;
    }
}

package org.wesome.graphql.entity;

public record Apple(Integer appleId, String appleName, String taste, Boolean available) {
}

package org.wesome.graphql.entity;

public record Vendor(Integer vendorId, Integer appleId, String firstName, String lastName, String address) {
}

package org.wesome.graphql.service;


import org.wesome.graphql.entity.Apple;

import java.util.List;

public interface AppleService {
    List<Apple> getAll();
}

package org.wesome.graphql.service;

import org.springframework.stereotype.Service;
import org.wesome.graphql.entity.Apple;

import java.util.List;

@Service
public class AppleServiceImpl implements AppleService {

    public static List<Apple> appleList;

    @Override
    public List<Apple> getAll() {
        return appleList;
    }
}

package org.wesome.graphql.service;


import org.wesome.graphql.entity.Apple;
import org.wesome.graphql.entity.Vendor;

import java.util.List;
import java.util.Map;

public interface VendorService {
    //get single vendor
    List<Vendor> getOneAppleVendor(Apple apple);

    Map<Apple, List<Vendor>> getAllAppleVendor(List<Apple> apple);
}

package org.wesome.graphql.service;

import org.springframework.stereotype.Service;
import org.wesome.graphql.entity.Apple;
import org.wesome.graphql.entity.Vendor;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

@Service
public class VendorServiceImpl implements VendorService {

    public static Map<Integer, List<Vendor>> vendorsList = new HashMap<>();

    @Override
    public Map<Apple, List<Vendor>> getAllAppleVendor(List<Apple> apple) {
        Map<Apple, List<Vendor>> appleListMap = apple.stream().collect(Collectors.toMap(app -> app, app -> vendorsList.get(app.appleId()), (a, b) -> b));
        return appleListMap;
    }

    @Override
    public List<Vendor> getOneAppleVendor(Apple apple) {
        return vendorsList.get(apple.appleId());
    }
}

package org.wesome.graphql;

import com.github.javafaker.Faker;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.wesome.graphql.data.AppleName;
import org.wesome.graphql.data.AppleTaste;
import org.wesome.graphql.entity.Apple;
import org.wesome.graphql.entity.Vendor;

import java.util.stream.Collectors;
import java.util.stream.IntStream;

import static org.wesome.graphql.service.AppleServiceImpl.appleList;
import static org.wesome.graphql.service.VendorServiceImpl.vendorsList;

@SpringBootApplication
public class GraphqlProjectApplication implements CommandLineRunner {

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

    @Override
    public void run(String... args) {
        Faker faker = new Faker();
        appleList = IntStream.rangeClosed(0, 3).mapToObj(app -> {
            var apple = new Apple(app, AppleName.values()[app].name(), AppleTaste.values()[app].name(), faker.random().nextBoolean());
            vendorsList.put(app, IntStream.rangeClosed(0, 1).mapToObj(ven -> new Vendor(ven, app, faker.name().firstName(), faker.name().lastName(), faker.address().fullAddress())).collect(Collectors.toList()));
            return apple;
        }).collect(Collectors.toList());
    }
}

# apple entity
type Apple{
    # primary key of apple
    appleId:ID!
    appleName:String
    taste:String
    available:Boolean
    vendors:[Vendor]
}

# apple entity
type Vendor{
    # primary key of Vendor
    vendorId:ID!
    appleId:Int
    firstName:String
    lastName:String
    address:String
}

type Query{
    # query to get all apples
    apples:[Apple]
}

\src\main\resources\application.properties

spring.graphql.graphiql.enabled=true

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
         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>3.1.5</version>
        <relativePath/>
    </parent>
    <groupId>org.wesome</groupId>
    <artifactId>spring-boot-graphql</artifactId>
    <version>0.0.1-snapshot</version>
    <name>spring-boot-graphql</name>
    <description>implementing graphql in spring boot</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.github.javafaker</groupId>
            <artifactId>javafaker</artifactId>
            <version>1.0.2</version>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.10.1</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-graphql</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webflux</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.graphql</groupId>
            <artifactId>spring-graphql-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>

Rest API

curl --location --request POST 'http://localhost:8080/graphql' \
--header 'Content-Type: application/json' \
--data '{"query":"query Apples { \r\n    apples {\r\n        appleId\r\n        appleName\r\n        taste\r\n        available\r\n        vendors {\r\n            vendorId\r\n            appleId\r\n            firstName\r\n            lastName\r\n            address\r\n        }\r\n    }\r\n}\r\n","variables":{}}'

GraphiQL

GraphQL provides an inbuild UserInterface GraphiQL, which can be accessed via http://localhost:8080/graphiql or access GraphQL via Postman, in the query section add the below query

query Apples { 
    apples {
        appleId
        appleName
        taste
        available
        vendors {
            vendorId
            appleId
            firstName
            lastName
            address
        }
    }
}

Spring Boot GraphQL N+1 Problem

follow us on