如何从Java应用程序调用GraphQL端点 [英] How to make a call to a GraphQL endpoint from a Java application

问题描述

我正在尝试调用GraphQL端点(外部的，不受我控制)，我在互联网上只能找到如何使用Java Spring Boot设置后端GraphQL端点.如何从Java应用程序调用GraphQL端点?

I am trying to make a call to a GraphQL endpoint (external, not controlled by me), all I can find on internet is how to setup a back-end GraphQL endpoint using Java Spring Boot. How do I call a GraphQL endpoint from a Java application?

推荐答案

Netflix DGS具有springboot客户端库.

Netflix DGS has springboot client libraries .

Ref: https://netflix.github.io/dgs/advanced/java-client/#http-client-wrapper

和

https://netflix.github.io/dgs/generating-code-from-schema/#generating-client-apis .

private RestTemplate dgsRestTemplate;

private static final String URL = "http://someserver/graphql";

private static final String QUERY = "{\n" +
            "  ticks(first: %d, after:%d){\n" +
            "    edges {\n" +
            "      node {\n" +
            "        route {\n" +
            "          name\n" +
            "          grade\n" +
            "          pitches\n" +
            "          location\n" +
            "        }\n" +
            "        \n" +
            "        userStars\n" +
            "      }\n" +
            "    }\n" +
            "  }\n" +
            "}";

public List<TicksConnection> getData() {
    DefaultGraphQLClient graphQLClient = new DefaultGraphQLClient(URL);
    GraphQLResponse response = graphQLClient.executeQuery(query, new HashMap<>(), (url, headers, body) -> {
        /**
         * The requestHeaders providers headers typically required to call a GraphQL endpoint, including the Accept and Content-Type headers.
         * To use RestTemplate, the requestHeaders need to be transformed into Spring's HttpHeaders.
         */
        HttpHeaders requestHeaders = new HttpHeaders();
        headers.forEach(requestHeaders::put);

        /**
         * Use RestTemplate to call the GraphQL service. 
         * The response type should simply be String, because the parsing will be done by the GraphQLClient.
         */
        ResponseEntity<String> exchange = dgsRestTemplate.exchange(url, HttpMethod.POST, new HttpEntity(body, requestHeaders), String.class);

        /**
         * Return a HttpResponse, which contains the HTTP status code and response body (as a String).
         * The way to get these depend on the HTTP client.
         */
        return new HttpResponse(exchange.getStatusCodeValue(), exchange.getBody());
    }); 

    TicksConnection ticks = graphQLResponse.extractValueAsObject("ticks", TicksConnection.class);
    return ticks;
}

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