nuaimat / graphql-java

GraphQL Java implementation

graphql-java

Friendly warning: As GraphQL itself is currently a Working Draft, expect changes.

This is a GraphQL Java implementation based on the specification and the JavaScript reference implementation.

Status/Plans: A first version is released. Future work will include more validations, logging and error reporting.

Table of Contents

• Overview
• Hello World
• Getting started
• Manual
  • Schema definition
  • Data fetching
  • Executing
  • Execution strategies
  • Logging
• Build it
• Details
• Acknowledgment
• Feedback
• License

Overview

This is a Java Implementation of GraphQL. The library aims for real-life usage in production.

It takes care of parsing and executing a GraphQL query. It doesn't take care of actually fetching any data: Data comes from implementing callbacks or providing static data.

Hello World

This is the famous "hello world" in graphql-java:

import graphql.schema.GraphQLObjectType;
import graphql.schema.GraphQLSchema;

import static graphql.Scalars.GraphQLString;
import static graphql.schema.GraphQLFieldDefinition.newFieldDefinition;
import static graphql.schema.GraphQLObjectType.newObject;

public class HelloWorld {

    public static void main(String[] args) {
    
        GraphQLObjectType queryType = newObject()
                .name("helloWorldQuery")
                .field(newFieldDefinition()
                        .type(GraphQLString)
                        .name("hello")
                        .staticValue("world")
                        .build())
                .build();

        GraphQLSchema schema = GraphQLSchema.newSchema()
                .query(queryType)
                .build();
        Map<String, Object> result = new GraphQL(schema).execute("{hello}").getResult();
        
        System.out.println(result);
        // Prints: {hello=world}
    }
}

Getting started

Gradle

The repository:

repositories {
    maven { url  "http://dl.bintray.com/andimarek/graphql-java" }
}

Dependency:

dependencies {
  compile 'graphql-java:graphql-java:1.0'
}

Maven

The repository:

<repository>
    <snapshots>
        <enabled>false</enabled>
    </snapshots>
    <id>bintray-andimarek-graphql-java</id>
    <name>bintray</name>
    <url>http://dl.bintray.com/andimarek/graphql-java</url>
</repository>

Dependency:

<dependency>
    <groupId>graphql-java</groupId>
    <artifactId>graphql-java</artifactId>
    <version>1.0</version>
</dependency>

Latest Version

For the latest version: Please clone and Build it.

Manual

Schema definition

Built-in Types

The Scalars Class has the following built-in types:

• GraphQLString
• GraphQLBoolean
• GraphQLInt
• GraphQLFloat

Creating a new Object Type

Example:

GraphQLObjectType simpsonCharacter = newObject()
    .name("SimpsonCharacter")
    .description("A Simpson character")
    .field(newFieldDefinition()
            .name("name")
            .description("The name of the character.")
            .type(GraphQLString)
            .build())
    .field(newFieldDefinition()
            .name("mainCharacter")
            .description("One of the main Simpson characters?")
            .type(GraphQLBoolean)
            .build())                    
.build();

Creating a new Interface Type

Example:

GraphQLObjectType comicCharacter = newObject()
    .name("ComicCharacter")
    .description("A abstract comic character.")
    .field(newFieldDefinition()
            .name("name")
            .description("The name of the character.")
            .type(GraphQLString)
            .build())
    .build();

Creating a new Union Type

Example: (a snippet from here)

PetType = GraphQLUnionType.newUnionType()
    .name("Pet")
    .possibleType(CatType)
    .possibleType(DogType)
    .typeResolver(new TypeResolver() {
        @Override
        public GraphQLObjectType getType(Object object) {
            if (object instanceof Cat) {
                return CatType;
            }
            if (object instanceof Dog) {
                return DogType;
            }
            return null;
        }
    })
    .build();
    

Creating a new Enum Type

Example:

GraphQLEnumType colorEnum = newEnum()
    .name("Color")
    .description("Supported colors.")
    .value("RED")
    .value("GREEN")
    .value("BLUE")
    .build();
       

Creating a Object-Input Type

Example

GraphQLInputObjectType inputObjectType = newInputObject()
    .name("inputObjectType")
    .field(newInputObjectField()
        .name("field")
        .type(GraphQLString)
        .build())
    .build()

Creating a Schema

Example:

GraphQLSchema schema = GraphQLSchema.newSchema()
    .query(queryType) // must be provided
    .mutation(mutationType) // is optional
    .build();
            

A full schema example: StarWarsSchema

Another schema example, including union types: GarfieldSchema

Data fetching

The actual data comes from DataFetcher objects.

Every field definition has a DataFetcher. When no one is configured, a PropertyDataFetcher is used.

PropertyDataFetcher fetches data from Map and Java Beans. So when the field name matches the Map key or the property name of the source Object, no DataFetcher is needed.

Example of configuring a custom DataFetcher:

DataFetcher calculateComplicatedValue = new DataFetcher() {
    @Override
    Object get(DataFetchingEnvironment environment) {
        // environment.getSource() is the value of the surrounding
        // object. In this case described by objectType
        Object value = ... // Perhaps getting from a DB or whatever 
        return value;
    }

GraphQLObjectType objectType = newObject()
    .name("ObjectType")
    .field(newFieldDefinition()
            .name("someComplicatedValue")
            .type(GraphQLString)
            .dataFetcher(calculateComplicatedValue)
            .build())
    .build();

Executing

To execute a Query/Mutation against a Schema instantiate a new GraphQL Object with the appropriate arguments and then call execute().

The result of a Query is a ExecutionResult Object with the result and/or a list of Errors.

Example: GraphQL Test

Complexer examples: StarWars query tests

Execution strategies

All fields in a SelectionSet are executed serially per default.

GraphQL takes as second constructor argument an optional ExecutorService. When provided fields will be executed parallel, except the first level of a mutation operation.

See specification for details.

It's recommended to use a ExecutorService to speed up execution.

Logging

Logging is done with SLF4J. Please have a lookout at the Manual for details. The grapqhl-java root Logger name is graphql.

Build it

Just clone the repo and type

./gradlew build

In build/libs you will find the jar file.

Running the tests:

./gradlew test

Installing in the local Maven repository:

./gradlew install

Details

The implementation is in Java 7, but the tests are in Groovy and Spock.

The query parsing is done with ANTLR. The grammar is here.

The only runtime dependencies are ANTLR and Slf4J.

Acknowledgment

This implementation is based on the js reference implementation. For example the StarWarSchema and the tests (among a lot of other things) are simply adapted to the Java world.

Feedback

I would appreciate any feedback via Twitter @andimarek or Pull request/Issue.

License

graphql-java is licensed under the MIT License. See LICENSE for details.

Copyright (c) 2015, Andreas Marek and Contributors

graphql-js License