Microservice SDK (java) best way to call unsupperted but available REST endpoints

[apes (Alexander Pester)]

What product/components do you use and which version/fix level are you on?

Java Microservice SDK 1016.0.117

What are you trying to achieve? Please describe it in detail.

I want to use functionality to upload and download binaries to events with my Microservice, see Cumulocity IoT - OpenAPI Specification

I suppose i have to inject com.cumulocity.sdk.client.RestConnector; and call methods:

//upload
restConnector.postFile(url, null, attachment, EventRepresentation.class);

//download
restConnector.get(url, MediaType.APPLICATION_OCTET_STREAM_TYPE);

My Questions:

1. Where is the best way to get the different parts of the url?

??platformUrl??+"/event/events/{{eventId}}/binaries";

If this method would be public: cumulocity-clients-java/EventApiImpl.java at 3b199d143918dea1d7c21f24c4031db5b4e0940a · SoftwareAG/cumulocity-clients-java · GitHub
I had no problem to consturct the URL for it. I could directly use EventApiImpl. However it is private, how could i construct that with new version?

2. What is the second parameter of method postFile i have set to null. It must be from type EventRepresentation, i don’t have a request body for uploading the file? I don’t understand how to initialize this parameter.

[Korbinian_Butz]

Can only comment on your first question…

Where is the best way to get the different parts of the url?

The platform URL should be available as environment variable C8Y_BASEURL.

See here: “[…]The Cumulocity IoT exposes the REST endpoint /user/currentUser. The microservice retrieves the Cumulocity IoT address from the C8Y_BASEURL operating system environment variable.”

[Harald_Meyer]

Be aware that C8Y_BASEURL will not work correctly in a multi-tenant microservice. In that case you can extract the platform url from the response to the /tenant/currentTenant endpoint.

Update: I might be wrong, will test and follow up.

[Stefan_Witschel]

@apes

What is the second parameter of method postFile i have set to null. It must be from type EventRepresentation, i don’t have a request body for uploading the file? I don’t understand how to initialize this parameter.

It seems to be the object:
https://cumulocity.com/api/core/10.15.0/#operation/postEventBinaryResource
and must contain something like this

{ "name": "hello.txt", "type": "text/plain" }

see here: https://github.com/SoftwareAG/cumulocity-clients-java/blob/3b199d143918dea1d7c21f24c4031db5b4e0940a/java-client/src/main/java/com/cumulocity/sdk/client/RestConnector.java#L209
Not sure why this has to be something like a Representation.

[apes (Alexander Pester)]

With new SDK and not allowing directly PlatformImpl and PlatformParameter, as i understand the output we don’t need that anymore:

Output:
Use relative URL’s starting with ‘/’ with RestConnector bean to have them resolved automatically against the host defined in PlatformParameters#getHost().

Which sounds good! I don’t need to care about the absolute url anymore.

[Michael_Voigt2 (Michael Voigt)]

Just to add a little note here: I played around with the RestConnector and even if you provide a full URL (incl the host like “https://something.com/…”) it will always connect to the host defined in PlatformParameters#getHost(): cumulocity-clients-java/CumulocityHttpClient.java at f188384ef58ba2a743226e1d338862fb9981b49a · SoftwareAG/cumulocity-clients-java · GitHub

The reason I looked into this is: I want to change the behavior of the RestConnector for some calls when running in my local development environment (Eclipse). Those calls that target a REST endpoint within my own microservice should execute against http://localhost:80/… so I can debug them accordingly. Anybody ever achieved this?

[apes (Alexander Pester)]

I have implemented it using restTemplates:

Created two pojos EventBinary and BinaryInfo:

@Data
public class BinaryInfo {
	/**
	 * Name of the binary object.
	 */
	private String name;

	/**
	 * Media type of the file.
	 */
	private String type;
}

@Data
public class EventBinary {
	/**
	 * Name of the attachment. If it is not provided in the request, it will be set as the event ID.
	 */
	private String name;

	/**
	 * A URL linking to this resource.
	 */
	private String self;

	/**
	 * Unique identifier of the event.
	 */
	private String source;

	/**
	 * Media type of the attachment.
	 */
	private String type;
}

And Api:

@Slf4j
@Service
public class EventAttachmentApi {
		
	private ContextService<MicroserviceCredentials> contextService;
	
	private EventApi eventApi;
	
	@Autowired
	public EventAttachmentApi(ContextService<MicroserviceCredentials> contextService, EventApi eventApi) {
		super();
		this.contextService = contextService;
		this.eventApi = eventApi;
	}
	

	public EventBinary uploadEventAttachment(final BinaryInfo binaryInfo, Resource resource, final String eventId) {
		EventRepresentation event = eventApi.getEvent(GId.asGId(eventId));
		if(event == null) {
			return null;
		}
		
		HttpHeaders headers = new HttpHeaders();
		headers.set("Authorization", contextService.getContext().toCumulocityCredentials().getAuthenticationString());
		headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
		headers.setContentType(MediaType.MULTIPART_FORM_DATA);
		
		MultipartBodyBuilder multipartBodyBuilder = new MultipartBodyBuilder();
		multipartBodyBuilder.part("object", binaryInfo, MediaType.APPLICATION_JSON);
		multipartBodyBuilder.part("file", resource, MediaType.TEXT_PLAIN);
		
		MultiValueMap<String,HttpEntity<?>> body = multipartBodyBuilder.build();
		HttpEntity<MultiValueMap<String, HttpEntity<?>>> requestEntity = new HttpEntity<>(body, headers);

		String serverUrl = event.getSelf() + "/binaries";
		RestTemplate restTemplate = new RestTemplate();
		ResponseEntity<EventBinary> response = restTemplate.postForEntity(serverUrl, requestEntity, EventBinary.class);
		if(response.getStatusCodeValue() >= 300) {
			log.error("Upload event binary failed with http code {}", response.getStatusCode().toString());;
			return null;
		}
		return response.getBody();
	}
	
}