Spring Boot + GraphQL + MongoDB example with Spring Data & graphql-java

In this tutorial, we’re gonna build a Spring Boot GraphQL example that will expose CRUD APIs to create, read, update and delete objects in MongoDB database with the help of graphql-java and Spring Data.

Related Post:
– Spring Boot with MongoDB CRUD example using Spring Data

More Practice:
– Spring Boot + GraphQL + MySQL example with Spring JPA & graphql-spring-boot-starter

Spring Boot CRUD GraphQL APIs with MongoDB Overview

We have two data models: Author and Tutorial with the fields like this.

Author {
  id: String
  name: String
  age: Integer
}

Tutorial {
  id: String
  title: String
  description: String
  author: Author
}

The goal of this example is to build a GraphQL APIs to do CRUD operations with MongoDB database using only one endpoint: /apis/graphql.

– Create an Author:

• GraphQL

mutation {
  createAuthor(
    name: "bezkoder",
    age: 27) {
      id name
  }
}

• Response

{
  "data": {
    "createAuthor": {
      "id": "5dd7644e572b4b0f3fc558c5",
      "name": "bezkoder"
    }
  }
}

– Create a Tutorial:

• GraphQL: requiring Tutorial id, title and author (name) for response

mutation {
  createTutorial (
    title: "Tutorial #1",
    description: "Tut#1 Description"
    author: "5dd7644e572b4b0f3fc558c5")
    {
      id title author { name }
    }
}

• Response

{
  "data": {
    "createTutorial": {
      "id": "5dd764a0572b4b0f3fc558c7",
      "title": "Tutorial #1",
      "author": {
        "name": "bezkoder"
      }
    }
  }
}

– Read all Authors:

• GraphQL

{
  findAllAuthors{
    id
    name
    age
  }
}

• Response

{
  "data": {
    "findAllAuthors": [
      {
        "id": "5dd7644e572b4b0f3fc558c5",
        "name": "bezkoder",
        "age": 27
      },
      {
        "id": "5dd7645f572b4b0f3fc558c6",
        "name": "zKoder",
        "age": 29
      }
    ]
  }
}

– Read all Tutorials:

• GraphQL

{
  findAllTutorials{
    id
    title
    description
    author{
      id
      name
    }
  }
}

• Response

{
  "data": {
    "findAllTutorials": [
      {
        "id": "5dd764a0572b4b0f3fc558c7",
        "title": "Tutorial #1",
        "description": "Tut#1 Description",
        "author": {
          "id": "5dd7644e572b4b0f3fc558c5",
          "name": "bezkoder"
        }
      },
      {
        "id": "5dd764dd572b4b0f3fc558c8",
        "title": "Tutorial #2",
        "description": "Tut#2 Description",
        "author": {
          "id": "5dd7644e572b4b0f3fc558c5",
          "name": "bezkoder"
        }
      },
      {
        "id": "5dd764ed572b4b0f3fc558c9",
        "title": "Tutorial #3",
        "description": "Tut#3 Description",
        "author": {
          "id": "5dd7645f572b4b0f3fc558c6",
          "name": "zKoder"
        }
      }
    ]
  }
}

– Update a Tutorial:

• GraphQL

mutation {
  updateTutorial (
    id: "5dd764dd572b4b0f3fc558c8"
    description: "Tut#2 updated Desc")
    {
      id title description author { name }
    }
}

• Response

{
  "data": {
    "updateTutorial": {
      "id": "5dd764dd572b4b0f3fc558c8",
      "title": "Tutorial #2",
      "description": "Tut#2 updated Desc",
      "author": {
        "name": "bezkoder"
      }
    }
  }
}

– Delete a Tutorial:

• GraphQL

mutation {
  deleteTutorial(id: "5dd764a0572b4b0f3fc558c7")
}

• Response

{
  "data": {
    "deleteTutorial": true
  }
}

– Count number of Tutorials:

• GraphQL

{
  countTutorials
}

• Response

{
  "data": {
    "countTutorials": 2
  }
}

Check MongoDB database, we have 2 collections like this:
authors

tutorials

The Spring Boot GraphQL Starter will make GraphQL server running in a short time.
The GraphQL Java Tools provides some Resolver interface that helps us to resolve values for GraphQL query & mutation requests.

Build Spring Boot GraphQL APIs with MongoDB Database

Technology

Our Spring Boot Project will use:

• Java 8
• Spring Boot 2.2.1.RELEASE (with Spring Web, Spring Data MongoDB)
• graphql-spring-boot-starter 5.0.2
• graphql-java-tools 5.2.4
• Maven 3.6.1
• MongoDB 3.4.x

Project Structure

This is folders & files structure for our Spring Boot + GraphQL + MongoDB application:

– resources/graphql contains .graphqls files that define GraphQL chemas.
– model holds two data models: Author and Tutorial.
– repository contains Repository interfaces to interact with MongoDB database.
– resolver resolves values for query & mutation requests by implementing some Resolver interfaces from GraphQL Java Tools.
– application.properties configures Spring Data MongoDB and GraphQL base Url.
– pom.xml includes dependencies for the whole project.

Set up the project

Create new Spring Boot project using Spring Tool Suite or going to https://start.spring.io/.

Then add these dependencies to pom.xml file:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
	<groupId>com.graphql-java</groupId>
	<artifactId>graphql-spring-boot-starter</artifactId>
	<version>5.0.2</version>
</dependency>

<dependency>
	<groupId>com.graphql-java</groupId>
	<artifactId>graphql-java-tools</artifactId>
	<version>5.2.4</version>
</dependency>

Configure Spring Data, GraphQL

Open application.properties and add the following configuration.

spring.data.mongodb.database=bezkoder_mongodb
spring.data.mongodb.port=27017

# Graphql
graphql.servlet.mapping: /apis/graphql

By default, Spring Boot GraphQL starter exposes the GraphQL Service on /graphql endpoint for HTTP POST requests containing the GraphQL payload. In the code above, we config the endpoint with new base url: /apis/graphql.

Create GraphQL Schema

We’re gonna split up your schema into two .graphqls files. The Spring Boot GraphQL starter will automatically find these schema files.

Under src/main/resources folder, create author.graphqls and tutorial.graphqls files.

author.graphqls

type Author {
	id: ID!
	name: String!
	age: Int
}

# Root
type Query {
	findAllAuthors: [Author]!
	countAuthors: Long!
}

# Root
type Mutation {
	createAuthor(name: String!, age: Int): Author!
}

GraphQL accepts only one root Query and one root Mutation types, so we need to bring all the query and mutation operations into the root Types. But in the schemas above, we want to split the logic for each model. How to do this? We extend the Query and Mutation types.

tutorial.graphqls

type Tutorial {
	id: ID!
	title: String!
	description: String
	author: Author
}

extend type Query {
	findAllTutorials: [Tutorial]!
	countTutorials: Long!
}

extend type Mutation {
	createTutorial(title: String!, description: String, author: ID!): Tutorial!
	updateTutorial(id: ID!, title: String, description: String): Tutorial!
	deleteTutorial(id: ID!): Boolean
}

The “!” at the end of some fields indicates non-nullable type. If we don’t use it, GraphQL accepts null value in the response.

Define Data Models

Now we define twom main models with One-to-Many Relationship in model package:

• Author: id, name, age
• Tutorial: id, title, description, author_id

Author.java

package com.bezkoder.springgraphql.mongodb.model;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document(collection = "authors")
public class Author {
  @Id
  private String id;
  private String name;
  private Integer age;

  public Author() {
  }

  public Author(String id) {
    this.id = id;
  }

  public Author(String name, Integer age) {
    this.name = name;
    this.age = age;
  }

  public String getId() {
    return id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Integer getAge() {
    return age;
  }

  public void setAge(Integer age) {
    this.age = age;
  }

  @Override
  public String toString() {
    return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
  }
}

Tutorial.java

package com.bezkoder.springgraphql.mongodb.model;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document(collection = "tutorials")
public class Tutorial {
  @Id
  private String id;
  private String title;
  private String description;
  private String author_id;

  public Tutorial() {
  }

  public Tutorial(String title, String description, String author_id) {
    this.title = title;
    this.description = description;
    this.author_id = author_id;
  }

  public String getId() {
    return id;
  }

  public String getTitle() {
    return title;
  }

  public void setTitle(String title) {
    this.title = title;
  }

  public String getDescription() {
    return description;
  }

  public void setDescription(String description) {
    this.description = description;
  }

  public String getAuthorId() {
    return author_id;
  }

  public void setAuthorId(String author_id) {
    this.author_id = author_id;
  }

  @Override
  public String toString() {
    return "Tutorial [id=" + id + ", title=" + title + ", description=" + description + ", author_id=" + author_id + "]";
  }
}

Create Repositories

In repository package, create two interfaces that implement MongoRepository.

AuthorRepository.java

package com.bezkoder.springgraphql.mongodb.repository;

import org.springframework.data.mongodb.repository.MongoRepository;

import com.bezkoder.springgraphql.mongodb.model.Author;

public interface AuthorRepository extends MongoRepository<Author, String> {

}

TutorialRepository.java

package com.bezkoder.springgraphql.mongodb.repository;

import org.springframework.data.mongodb.repository.MongoRepository;

import com.bezkoder.springgraphql.mongodb.model.Tutorial;

public interface TutorialRepository extends MongoRepository<Tutorial, String> {

}

Once we extends the MongoRepository, Spring Data MongoDB will automatically generate implementation with find, save, delete, count methods for the Documents.

Implement GraphQL Root Query Resolver

Every field in the schema root query should have a method in the Query Resolver class with the same name.

Now look back to the schemas we defined above.

# author.graphqls
type Query {
	findAllAuthors: [Author]!
	countAuthors: Long!
}

# tutorial.graphqls
extend type Query {
	findAllTutorials: [Tutorial]!
	countTutorials: Long!
}

This Query class implements GraphQLQueryResolver.

resolver/Query.java

package com.bezkoder.springgraphql.mongodb.resolver;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.bezkoder.springgraphql.mongodb.model.Author;
import com.bezkoder.springgraphql.mongodb.model.Tutorial;
import com.bezkoder.springgraphql.mongodb.repository.AuthorRepository;
import com.bezkoder.springgraphql.mongodb.repository.TutorialRepository;
import com.coxautodev.graphql.tools.GraphQLQueryResolver;

@Component
public class Query implements GraphQLQueryResolver {
  private AuthorRepository authorRepository;
  private TutorialRepository tutorialRepository;

  @Autowired
  public Query(AuthorRepository authorRepository, TutorialRepository tutorialRepository) {
    this.authorRepository = authorRepository;
    this.tutorialRepository = tutorialRepository;
  }

  public Iterable<Author> findAllAuthors() {
    return authorRepository.findAll();
  }

  public Iterable<Tutorial> findAllTutorials() {
    return tutorialRepository.findAll();
  }

  public long countAuthors() {
    return authorRepository.count();
  }

  public long countTutorials() {
    return tutorialRepository.count();
  }

}

Implement GraphQL Root Mutation Resolver

Mutation class will implement GraphQLMutationResolver.
Just like Query Resolver, every field in the schema mutation query should have a method in the Mutation Resolver class with the same name.

resolver/Mutation.java

package com.bezkoder.springgraphql.mongodb.resolver;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.bezkoder.springgraphql.mongodb.model.Author;
import com.bezkoder.springgraphql.mongodb.model.Tutorial;
import com.bezkoder.springgraphql.mongodb.repository.AuthorRepository;
import com.bezkoder.springgraphql.mongodb.repository.TutorialRepository;
import com.coxautodev.graphql.tools.GraphQLMutationResolver;

@Component
public class Mutation implements GraphQLMutationResolver {
  private AuthorRepository authorRepository;
  private TutorialRepository tutorialRepository;

  @Autowired
  public Mutation(AuthorRepository authorRepository, TutorialRepository tutorialRepository) {
    this.authorRepository = authorRepository;
    this.tutorialRepository = tutorialRepository;
  }

  public Author createAuthor(String name, Integer age) {
    Author author = new Author();
    author.setName(name);
    author.setAge(age);

    authorRepository.save(author);

    return author;
  }

  public Tutorial createTutorial(String title, String description, String authorId) {
    Tutorial book = new Tutorial();
    book.setAuthorId(authorId);
    book.setTitle(title);
    book.setDescription(description);

    tutorialRepository.save(book);

    return book;
  }

  public boolean deleteTutorial(String id) {
    tutorialRepository.deleteById(id);
    return true;
  }

  public Tutorial updateTutorial(String id, String title, String description) throws Exception {
    Optional<Tutorial> optTutorial = tutorialRepository.findById(id);

    if (optTutorial.isPresent()) {
      Tutorial tutorial = optTutorial.get();

      if (title != null)
        tutorial.setTitle(title);
      if (description != null)
        tutorial.setDescription(description);

      tutorialRepository.save(tutorial);
      return tutorial;
    }

    throw new Exception("Not found Tutorial to update!");
  }

}

Implement GraphQL Field Resolver

For complex fields like author in Tutorial, we have to resolve the value of those fields.
TutorialResolver implements GraphQLResolver interface and has getAuthor() method.

resolver/TutorialResolver.java

package com.bezkoder.springgraphql.mongodb.resolver;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.bezkoder.springgraphql.mongodb.model.Author;
import com.bezkoder.springgraphql.mongodb.model.Tutorial;
import com.bezkoder.springgraphql.mongodb.repository.AuthorRepository;
import com.coxautodev.graphql.tools.GraphQLResolver;

@Component
public class TutorialResolver implements GraphQLResolver<Tutorial> {
  @Autowired
  private AuthorRepository authorRepository;

  public TutorialResolver(AuthorRepository authorRepository) {
    this.authorRepository = authorRepository;
  }

  public Author getAuthor(Tutorial tutorial) {
    return authorRepository.findById(tutorial.getAuthorId()).orElseThrow(null);
  }
}

If the client want to get a Tutorial without author field, the GraphQL Server will never do the work to retrieve it. So the getAuthor() method above will never be executed.

Run & Check result

Run Spring Boot application with command: mvn spring-boot:run.

For checking result, you can use Postman to make HTTP POST request to http://localhost:8080/apis/graphql.

Conclusion

Today we’ve learned how to use the GraphQL Java Tools to build a Spring Boot CRUD GraphQL Apis that can communicate with MongoDB database using Spring Data MongoDB.

Happy learning! See you again.

Further Reading

• GraphQL documentation
• https://www.graphql-java.com/tutorials/getting-started-with-spring-boot/
• graphql-java Github
• Spring Data MongoDB – Reference Documentation