Java example to fetch tridion content service PCA graphql response.

- Implementation which is available is built on spring-boot framework, I am gonna put only relative information on graphql and java client.

I have prepared one class which is having few example of tridion pca graphql queries using java,

QueryService.java

@Service
public class QueryService {

    final PCAClientProvider pcaClientProvider;

    public QueryService(PCAClientProvider pcaClientProvider) {
        this.pcaClientProvider = pcaClientProvider;
    }

    protected ApiClient getPcaClient() {
        ApiClient pcaClient = this.pcaClientProvider.getClient();
        pcaClient.setDefaultModelType(DataModelType.R2);
        pcaClient.setDefaultContentType(ContentType.MODEL);
        pcaClient.setModelServiceLinkRenderingType(ModelServiceLinkRendering.RELATIVE);
        pcaClient.setTcdlLinkRenderingType(TcdlLinkRendering.RELATIVE);
        return pcaClient;
    }

    protected CustomApiClient getCustomPcaClient() {
        CustomApiClient pcaClient = this.pcaClientProvider.getCustomClient();
        pcaClient.setDefaultModelType(DataModelType.R2);
        pcaClient.setDefaultContentType(ContentType.MODEL);
        pcaClient.setModelServiceLinkRenderingType(ModelServiceLinkRendering.RELATIVE);
        pcaClient.setTcdlLinkRenderingType(TcdlLinkRendering.RELATIVE);
        return pcaClient;
    }

    public Publication getPublicationTitle(int pubId) {
        return getPcaClient().getPublication(ContentNamespace.Sites, pubId, "", null);
    }

    public Page getPage(int publicationId, int pageId) {
        return getPcaClient().getPage(ContentNamespace.Sites, publicationId, pageId, "", ContentIncludeMode.INCLUDE_DATA, null);
    }

    public PublicationConnection getAllPublications() {
        Pagination pagination = new Pagination();
        pagination.first = 0;
        pagination.after = "";
        return getPcaClient().getPublications(ContentNamespace.Sites, pagination, null, "", null);
    }

    public ComponentPresentation getComponentPresentations(int publicationId, int componentId, int templateId) {
        return getPcaClient().getComponentPresentation(ContentNamespace.Sites, publicationId, componentId, templateId, "", ContentIncludeMode.INCLUDE_DATA, null);
    }

    public BinaryComponent getBinaryComponent(int publicationId, int binaryId) {
        return getPcaClient().getBinaryComponent(ContentNamespace.Sites, publicationId, binaryId, "", null);
    }

    public ComponentPresentationConnection getComponentPresentations(int publicationId) {
        Pagination pagination = new Pagination();
        pagination.first = 0;
        pagination.after = "";
        InputComponentPresentationFilter inputComponentPresentationFilter = new InputComponentPresentationFilter();
        InputSortParam sortParam = new InputSortParam();
        sortParam.setOrder(SortOrderType.Descending);
        return getPcaClient().getComponentPresentations(ContentNamespace.Sites, publicationId, inputComponentPresentationFilter,
                sortParam, pagination, "", ContentIncludeMode.INCLUDE_DATA, null);
    }

    public String resolveComponentLink(int publicationId, int targetComponentId, int sourcePageId, int excludeComponentTemplateId, boolean renderRelativeLink) {
        return getPcaClient().resolveComponentLink(ContentNamespace.Sites, publicationId, targetComponentId, sourcePageId, excludeComponentTemplateId, renderRelativeLink);
    }

    public JsonNode getCategories(int publicationId) {
        return getCustomPcaClient().getCategories(ContentNamespace.Sites, publicationId);
    }
}

for class PCAClientProvider we can take a reference from dxa github repo
https://github.com/RWS/dxa-web-application-java/blob/6e475a85a52d7b8190572662674b43c0d3056fba/dxa-framework/dxa-tridion-common/src/main/java/com/sdl/dxa/tridion/pcaclient/DefaultApiClientProvider.java

we need to have following dependency in the project in order to get PCAClient references.

<dependency>
    <groupId>com.sdl.web.pca</groupId>
    <artifactId>pca-client</artifactId>
    <version>2.2.16</version>
</dependency>

to understand QueryService we can also refer following junit test class

@SpringBootTest
public class QueryServiceTest {

    @Autowired
    QueryService queryService;

    @Test
    public void fetchAllPublication() {
        PublicationConnection allPublications = queryService.getAllPublications();
        assertThat(allPublications, is(notNullValue()));
        System.out.printf("total number of web publications are: %d%n", allPublications.getEdges().size());
    }

    @Test
    public void fetchAllCategories() {
        int publicationId = 25;
        JsonNode categories = queryService.getCategories(publicationId);
        assertThat(categories, is(notNullValue()));
        System.out.printf("published categories in publication %d%n are: %s%n", publicationId, categories.toPrettyString());
    }

    @Test
    public void fetchBinaryComponent() {
        BinaryComponent binaryComponent = queryService.getBinaryComponent(25, 1580);
        assertThat(binaryComponent, is(notNullValue()));
        System.out.printf("Binary Component id is %s: ", binaryComponent.getId());
    }
}

we can also write our own ApiClient in order to get response based on custom query or criteria
for example
public class CustomApiClient extends DefaultApiClient {

    private static final Logger LOG = LoggerFactory.getLogger(CustomApiClient.class);
    private static final ObjectMapper MAPPER = new ObjectMapper();
    private final GraphQLClient graphQLClient;
    private final int requestTimeout;

    public CustomApiClient(GraphQLClient graphQLClient, int requestTimeout) {
        super(graphQLClient, requestTimeout);
        this.graphQLClient = graphQLClient;
        this.requestTimeout = (int) TimeUnit.MILLISECONDS.toMillis(requestTimeout);
    }

    public JsonNode getCategories(ContentNamespace ns, int publicationId) {
        GraphQLRequest graphQLRequest = (new PCARequestBuilder()).withQuery("AllCategories").withNamespace(ns).withPublicationId(publicationId).withTimeout(this.requestTimeout).build();
        Class<JsonNode> clazz = JsonNode.class;
        String path = "/data/categories";
        return getResultForRequest(graphQLRequest, clazz, path);
    }

    private <T> T getResultForRequest(GraphQLRequest request, Class<T> clazz, String path) throws ApiClientException {
        JsonNode result = getJsonResult(request, path);
        try {
            return MAPPER.treeToValue(result, clazz);
        } catch (JsonProcessingException e) {
            throw new ApiClientException("Unable map result to " + clazz.getName() + ": " + result.toString(), e);
        }
    }

    private JsonNode getJsonResult(GraphQLRequest request, String path) throws ApiClientException {
        int attempt = 3;
        UnauthorizedException[] exception = new UnauthorizedException[1];
        while (attempt > 0) {
            try {
                attempt--;
                return getJsonResultInternal(request, path);
            } catch (UnauthorizedException ex) {
                if (exception[0] == null) exception[0] = ex;
                LOG.error("Could not perform query on " + path);
            }
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                break;
            }
        }
        throw new ApiClientException("Could not perform query " + request + " after 3 attempts", exception[0]);
    }

    private JsonNode getJsonResultInternal(GraphQLRequest request, String path) throws ApiClientException, UnauthorizedException {
        try {
            String resultString = this.graphQLClient.execute(request);
            JsonNode resultJson = MAPPER.readTree(resultString);
            return resultJson.at(path);
        } catch (GraphQLClientException e) {
            throw new ApiClientException("Unable to execute query: " + request, e);
        } catch (IOException e) {
            throw new ApiClientException("Unable to deserialize result for query " + request, e);
        }
    }
}