CODEWITHSUNDEEP
javagraphqlgraphql-java
Ajit
Ajit

Reputation: 23

How to programmatically read the schema of a GraphQL query in Java?

I am working with a GraphQL API provided by an upstream system. In my application, I need to dynamically fetch the possible values for an argument in the GraphQL query. The upstream system's team has defined an enum type for this argument, containing a list of possible values.

For example, let's say the argument is country, and the enum contains a list of countries.

How can I programmatically retrieve these enum values in Java so that I can dynamically construct my GraphQL queries?

Here's an overview of what I'm trying to achieve:

1-Query the GraphQL schema to fetch the possible values for the country argument.

2-Use these values to dynamically construct GraphQL queries.

3-Execute the constructed queries against the GraphQL API.

I'm using the graphql-java library for handling GraphQL operations in my Java application.

Any help or pointers would be greatly appreciated! Thanks in advance.

Upvotes: 0

Views: 599

Answers (1)

lance-java
lance-java

Reputation: 27994

You can likely use introspection for this

This has just scratched the surface of the introspection system; we can query for enum values, what interfaces a type implements, and more

I can see some introspection classes here in the graphql-java client sources which might be a good place to start

Perhaps the IntrospectionQueryBuilder might be a starting point

I asked ChatGPT how to do this which provided the following code sample. No idea if it's hallucinating or not

import graphql.GraphQL;
import graphql.introspection.IntrospectionQuery;
import graphql.introspection.IntrospectionResultToSchema;
import graphql.schema.GraphQLSchema;
import graphql.GraphQLException;
import java.util.List;
import java.util.stream.Collectors;

public class GraphQLClient {

    public static void main(String[] args) {
        String graphqlEndpoint = "http://example.com/graphql"; // Replace with your GraphQL server endpoint

        // Send an introspection query to fetch the schema
        GraphQL graphQL = GraphQL.newGraphQL(buildGraphQLSchema(graphqlEndpoint)).build();
        String schemaJson = graphQL.execute(IntrospectionQuery.INTROSPECTION_QUERY).getData().toString();

        // Parse the schema JSON into a GraphQLSchema object
        GraphQLSchema graphQLSchema = new IntrospectionResultToSchema().createSchema(IntrospectionResultToSchema.parse(schemaJson));

        // Now you can work with the GraphQLSchema object
        // For example, you can retrieve enum values for a specific type
        // Let's assume you want to get possible values for an enum field called "status" in a type called "User"
        // Replace "User" and "status" with your actual type and field names
        // This is just a sample, you need to adapt it to your schema structure

        // Replace "User" with your actual type name
        GraphQLObjectType userObjectType = graphQLSchema.getObjectType("User");

        // Replace "status" with your actual field name
        GraphQLEnumType statusEnumType = (GraphQLEnumType) userObjectType.getFieldDefinition("status").getType();

        // Now you can get the possible enum values
        List<String> enumValues = statusEnumType.getValues().stream().map(GraphQLEnumValueDefinition::getName).collect(Collectors.toList());

        System.out.println("Possible values for 'status' enum:");
        System.out.println(enumValues);
    }

    private static GraphQLSchema buildGraphQLSchema(String graphqlEndpoint) {
        try {
            // Replace "http://example.com/graphql" with your actual GraphQL server endpoint
            return GraphQLSchema.newSchema()
                    .query(GraphQLSchema.newQuery().build())
                    .build();
        } catch (Exception e) {
            throw new GraphQLException("Failed to build GraphQL schema from endpoint: " + graphqlEndpoint, e);
        }
    }
}

Upvotes: 0

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