GraphQL Java Print Schema - Java

GraphQL Java is a library for building GraphQL APIs in Java. With GraphQL Java, developers can define their schema using Java classes, and then use those classes to generate a GraphQL schema.

Installing GraphQL Java

To use GraphQL Java in your project, you can add the following dependency to your build.gradle file:

dependencies {
    implementation 'com.graphql-java:graphql-java:16.2.0'
    implementation 'com.graphql-java:graphql-java-tools:5.2.4'
}

Defining a GraphQL Schema in Java

To define a GraphQL schema in Java, you need to create a Java class that represents your GraphQL type. For example, if you want to define a Person type, you can create a Person class like this:

public class Person {
    private int id;
    private String name;
    private List<Address> addresses;

    public Person(int id, String name, List<Address> addresses) {
        this.id = id;
        this.name = name;
        this.addresses = addresses;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public List<Address> getAddresses() {
        return addresses;
    }
}

The Person class has three fields: id, name, and addresses. Each field has a getter method to access the value.

To define a GraphQL schema, you need to use the GraphQLSchema class. Here's an example of how you can define a schema for the Person type:

GraphQLObjectType personType = GraphQLObjectType.newObject()
        .name("Person")
        .field(field -> field.name("id").type(Scalars.GraphQLInt))
        .field(field -> field.name("name").type(Scalars.GraphQLString))
        .field(field -> field.name("addresses").type(GraphQLList.list(newObject(Address))))
        .build();

GraphQLSchema schema = GraphQLSchema.newSchema()
        .query(GraphQLObjectType.newObject()
                .name("Query")
                .field(field -> field
                        .name("person")
                        .type(personType)
                        .argument(arg -> arg.name("id").type(Scalars.GraphQLInt))
                        .dataFetcher(dataFetchingEnvironment -> {
                            int id = dataFetchingEnvironment.getArgument("id");
                            return new Person(id, "John Doe", new ArrayList<>());
                        })))
        .build();

This schema defines a root query field called person, which takes an id argument and returns a Person object. The Person object has an id, name, and addresses field.

Printing a GraphQL Schema in Java

To print a GraphQL schema in Java, you can use the SchemaPrinter class. Here's an example of how you can print the Person schema we defined earlier:

String schemaString = new SchemaPrinter().print(schema);
System.out.println(schemaString);

This will print the following schema:

type Person {
  id: Int
  name: String
  addresses: [Address]
}

type Query {
  person(id: Int): Person
}

Conclusion

In conclusion, GraphQL Java is a powerful library that allows you to define and generate a GraphQL schema in Java. With the SchemaPrinter class, you can easily print out your GraphQL schema in a readable format.