How to execute graphql in java?

by darrion.kuhn , in category: Javascript , 17 days ago

How to execute graphql in java?

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1 answer

by herminia_bruen , 16 days ago

@darrion.kuhn 

To execute GraphQL in Java, you can use libraries such as graphql-java or graphql-java-kickstart. Here's a basic outline of how you can execute GraphQL queries in Java using graphql-java library:

  1. Add the graphql-java dependency to your project. You can do this by adding the following dependency to your pom.xml file:
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<dependency>
    <groupId>com.graphql-java</groupId>
    <artifactId>graphql-java</artifactId>
    <version>{version}</version>
</dependency>


  1. Create a GraphQL schema using the graphql-java API. This schema defines the types and queries that your GraphQL service supports.
  2. Parse the incoming GraphQL query using graphql-java's GraphQLParser class.
  3. Execute the parsed query against the GraphQL schema using graphql-java's GraphQL class. This will return a ExecutionResult object that contains the results of the query.
  4. Convert the ExecutionResult object into a JSON response that can be sent back to the client.


Here's a basic example of how you can execute a GraphQL query in Java using graphql-java library:

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import graphql.ExecutionInput;
import graphql.ExecutionResult;
import graphql.GraphQL;
import graphql.GraphQLContext;
import graphql.analysis.MaxQueryComplexityInstrumentation;
import graphql.analysis.MaxQueryDepthInstrumentation;
import graphql.language.SourceLocation;
import graphql.validation.ValidationError;

import java.util.List;

public class GraphQLExecutor {

    public static void main(String[] args) {
        // Create a GraphQL schema
        GraphQLSchema schema = GraphQLSchema.newSchema()
                .query(query -> query)
                .build();

        // Parse the incoming GraphQL query
        String query = "{ hello }";
        ExecutionInput executionInput = ExecutionInput.newExecutionInput()
                .query(query)
                .context(new Object())
                .build();

        // Execute the parsed query against the schema
        GraphQL graphQL = GraphQL.newGraphQL(schema)
                .instrumentation(new MaxQueryComplexityInstrumentation(5))
                .instrumentation(new MaxQueryDepthInstrumentation(3))
                .build();
        ExecutionResult executionResult = graphQL.execute(executionInput);

        // Handle the result
        if (!executionResult.getErrors().isEmpty()) {
            List<ValidationError> errors = executionResult.getErrors();
            for (ValidationError error : errors) {
                System.out.println("Error: " + error.getMessage());
            }
        } else {
            Object data = executionResult.getData();
            System.out.println("Result: " + data);
        }
    }
}


This is just a basic example to get you started. You can further customize your GraphQL execution by adding more instrumentation and error handling based on your specific requirements.