Spring Boot GraphQL Schema Union

A Union is a combination of multiple values, it describes the list of possible objects, and GraphQL provides a Union Type.

package org.wesome.graphql.controllers;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.graphql.data.method.annotation.Argument;
import org.springframework.graphql.data.method.annotation.MutationMapping;
import org.springframework.graphql.data.method.annotation.QueryMapping;
import org.springframework.stereotype.Controller;
import org.wesome.graphql.entity.Apple;
import org.wesome.graphql.entity.AppleVO;
import org.wesome.graphql.service.AppleService;

import java.util.List;

@Controller
public class AppleGraphQLController {
    @Autowired
    private AppleService appleService;

    @QueryMapping("findAllApple")
    List<Apple> findAllApple() {
        return appleService.findAllApple();
    }

    @MutationMapping("addApple")
    Apple addApple(@Argument AppleVO appleVO) {
        return appleService.addApple(appleVO);
    }
}

package org.wesome.graphql.entity;

public interface Apple {
    public int getAppleId();

    public String getAppleName();

    public Boolean getAvailable();
}

package org.wesome.graphql.entity;

public enum AppleEnum {
    MACINTOSH, FUJI
}

package org.wesome.graphql.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.EqualsAndHashCode;

@Data
@EqualsAndHashCode
@AllArgsConstructor
public final class AppleVO {
    private String appleName;
    private Boolean available;
    private AppleEnum appleType;
}

package org.wesome.graphql.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.EqualsAndHashCode;

@Data
@EqualsAndHashCode
@AllArgsConstructor
public final class Fuji implements Apple {
    private int appleId;
    private String appleName;
    private Boolean available;
}

package org.wesome.graphql.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.EqualsAndHashCode;

@Data
@EqualsAndHashCode
@AllArgsConstructor
public final class Macintosh implements Apple {
    private int appleId;
    private String appleName;
    private Boolean available;
}

package org.wesome.graphql.service;

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

import java.util.List;

public interface AppleService {
    List<Apple> findAllApple();

    Apple addApple(AppleVO appleVO);
}

package org.wesome.graphql.service;

import org.springframework.stereotype.Service;
import org.wesome.graphql.entity.Apple;
import org.wesome.graphql.entity.AppleEnum;
import org.wesome.graphql.entity.AppleVO;
import org.wesome.graphql.entity.Fuji;
import org.wesome.graphql.entity.Macintosh;

import java.util.ArrayList;
import java.util.List;

@Service
public class AppleServiceImpl implements AppleService {
    private static final List<Apple> apples = new ArrayList<>(List.of(new Macintosh(1, "Macintosh A", true), new Macintosh(2, "Macintosh B", false), new Fuji(3, "Fuji A", true), new Fuji(4, "Fuji B", false)));

    @Override
    public List<Apple> findAllApple() {
        return apples;
    }

    @Override
    public Apple addApple(AppleVO appleVO) {
        Apple apple = null;
        if (appleVO.getAppleType() == AppleEnum.FUJI) {
            apple = new Fuji(apples.size() + 1, appleVO.getAppleName(), appleVO.getAvailable());
        } else if (appleVO.getAppleType() == AppleEnum.MACINTOSH) {
            apple = new Macintosh(apples.size() + 1, appleVO.getAppleName(), appleVO.getAvailable());
        }
        apples.add(apple);
        return apple;
    }
}

package org.wesome.graphql;

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

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

\src\main\resources\graphql\schema.graphqls

#"""
#A custom scalar must be declared explicitly.
#"""
scalar DateTime
# Apple Object
type Apple{
    # primary key of apple
    appleId:ID!
    # apple Name
    appleName:String
    # local Date
    dateCreated: DateTime
}

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

\src\main\resources\application.properties

spring.graphql.graphiql.enabled=true

<?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.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-graphql</artifactId>
        <dependency>
            <groupId>com.graphql-java</groupId>
            <artifactId>graphql-java-extended-scalars</artifactId>
            <version>21.0</version>
        </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>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

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 FindAllApple {
    findAllApple {
        __typename
        ... on Macintosh {
            appleId
            available
            appleName
        }
        ... on Fuji {
            appleId
            available
            appleName
        }
    }
}

For Mutation, use the below query

mutation AddApple {
    addApple(
        appleVO: { available: true, appleName: "Macintosh C", appleType: MACINTOSH }
    ) {
        ... on Macintosh {
            appleId
            available
            appleName
        }
        ... on Fuji {
            appleId
            available
            appleName
        }
    }
}