Access an attachment on the server

Data Services
1

I am trying to access an attachment on the server. My use case involves uploading a CSV file and converting the entries into documents.

I have found several threads here regarding the attachment, but every response suggests that I need to download the file. I don’t understand this because I have just uploaded it and want to use it after document creation. All internal implementations capable of returning the file are either deprecated or unavailable, as far as I have found. :sweat_smile:

The only method I’ve discovered to achieve what I want is to use the AttachmentAfterUpload event, but I can’t be certain that the user won’t cancel the operation at this point.

Is there a way to access the file and retrieve its contents?

2

If you want to access an already saved attachment in the backend using the content id this solution is probably the easiest way using non-internal A12 components.

But

My use case involves uploading a CSV file and converting the entries into documents.

sounds like not using the ContentStore but instead creating a custom REST endpoint for the upload may be a better solution. There you can parse the file & create the documents without needing to write and read the attachment to the filesystem

3

My ideal scenario is to use the DocumentAfterCreateEvent because we are also storing some metadata with the upload.

Certainly, a custom endpoint and a custom component could address that issue. However, we’re interested in knowing how to handle this in A12.

I already came across the post you linked, but it felt like more of a workaround. Is there another reason for the service? I’m curious why you would rename “attachment” to “content” if it’s an attachment service.

5

Moin @soeren-round-ridge,

if you want to access the attachment that has been created right before the DocumentAfterCreateEvent, you could try the following:

package com.mgmtp.a12.template.server.attachment;

import com.mgmtp.a12.contentstore.service.ContentStoreService;
import com.mgmtp.a12.dataservices.document.events.DocumentAfterCreateEvent;
import com.mgmtp.a12.dataservices.events.DataServicesEventListener;
import com.mgmtp.a12.kernel.md.document.api.IDocument;
import com.mgmtp.a12.kernel.md.document.api.IFieldInstance;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.nio.charset.StandardCharsets;

@Component
public class AttachmentListener {

    @Autowired
    ContentStoreService contentStoreService;

    @DataServicesEventListener
    public void beforeDocumentCreate(DocumentAfterCreateEvent event) throws IOException {
        String attachmentId = getFieldInstanceFromDocument(event.getDataServicesDocument().getKernelDocument(), "/Person/PersonalData/Photo/attachment_id").getValue().get().toString();

        String contentUrl = contentStoreService.requestContentUrl(attachmentId, 60L);
        String ticketId = contentUrl.substring(contentUrl.lastIndexOf("/") + 1);
        byte[] bytes = contentStoreService.getContent(ticketId).getContentSupplier().get().readAllBytes();
        String result = new String(bytes, StandardCharsets.UTF_8);

        // Do something with the attachment content "result"
        System.out.println(result);
    }

    private IFieldInstance getFieldInstanceFromDocument(IDocument document, String path) {
        return document.getEntityInstances().stream()
                .filter(instance -> instance.getPath().equals(path))
                .findFirst()
                .map(IFieldInstance.class::cast)
                .orElseThrow();
    }
}

Please also check if you have configured the content to be stored in the content store database. Per default, the attachment content is stored on file system (~/a12/dataservices/).
You could change the behaviour by configuring the following:

mgmtp.a12.dataservices.contentstore.storage.contentStorage=DB

Like @tim-steep-bit mentioned, otherwise it’s not possible to access the attachment’s content. The AttachmentService only provides functionality for retrieving either the attachment- or thumbnail url.
If you want to access the actual attachment’s content, you use the ContentStoreService.

(Depends on if you are using the content store, and have it configured)