After completing self-learning the Java software programming language and the Spring Boot backend web app development framework in about a couple of weeks, I’ll get to creating and publishing a GraphQL query and mutation demo with database CRUD (Create, Read, Update, and Delete) operations.
HTTP is the most common choice for client-server protocol when using GraphQL.
The official GraphQL reference gives some guidelines for setting up a GraphQL server to operate over HTTP.
(Early-plugs insertion point. A few seconds of silence in audiovisual.)
Most modern web frameworks use a pipeline model where requests are passed through a stack of middleware (AKA filters/plugins). As the request flows through the pipeline, it can be inspected, transformed, modified, or terminated with a response. GraphQL should be placed after all authentication middleware, so that you have access to the same session and user information you would in your HTTP endpoint handlers.
HTTP is commonly associated with REST, which uses “resources” as its core concept. In contrast, GraphQL’s conceptual model is an entity graph. As a result, entities in GraphQL are not identified by URLs. Instead, a GraphQL server operates on a single URL/endpoint, usually /graphql, and all GraphQL requests for a given service should be directed at this endpoint.
Your GraphQL HTTP server should handle the HTTP GET and POST methods.
When receiving an HTTP GET request, the GraphQL query should be specified in the “query” query string.
Query variables can be sent as a JSON-encoded string in an additional query parameter called variables. If the query contains several named operations, an operationName query parameter can be used to control which one should be executed.
A standard GraphQL POST request should use the application/json content type, and include a JSON-encoded body. operationName and variables are optional fields. operationName is only required if multiple operations are present in the query.
Regardless of the method by which the query and variables were sent, the response should be returned in the body of the request in JSON format. As mentioned in the spec, a query might result in some data and some errors, and those should be returned in a JSON object. If there were no errors returned, the “errors” field should not be present on the response. If no data is returned, according to the GraphQL spec, the “data” field should only be included if no errors occurred during execution.
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