Follow-up to previous posts, now using the standard Jakarta RESTful Web Services approach, with type jakarta.ws.rs.core.EntityPart.

In fact, while the Liberty documentation still describes the “old” way of doing this, it explicitly says that is deprecated and links to the above content for the “new” way.

So, while there’s not much to add to that official Jakarta documentation, I’ll go ahead and share the equivalent code that replaces our prior, Liberty-specific versions.

Maven dependency

        <dependency>
            <groupId>jakarta.ws.rs</groupId>
            <artifactId>jakarta.ws.rs-api</artifactId>
            <version>4.0.0</version>
            <scope>provided</scope>
        </dependency>

Java Resource

package your.package;
...
import jakarta.ws.rs.Consumes;
import jakarta.ws.rs.POST;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.core.EntityPart;
import jakarta.ws.rs.core.MediaType;
import jakarta.ws.rs.core.Response;
import jakarta.ws.rs.core.Response.Status;
...
public class ExampleFileUploadResource {

    ...
      
    @POST
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    @Produces(MediaType.TEXT_PLAIN)	// or whatever you want for response type
    public Response submitFile(List<EntityPart> parts) 
    {
        File file = null;
        Map<String, String> params = new HashMap<>();

        for (EntityPart part : parts) {

            if (part == null) {
                log.warn("Empty part found");
                continue;
            }

            String partName = part.getName();
            if (partName == null) {
                log.warn("Nameless part found");
                continue;
            }

            log.debug("partName: {}, mediaType: {}", partName, part.getMediaType());

            Optional<String> fileName = part.getFileName();

            // look for filename to determine files vs. parameters
            if (fileName.isPresent()) {

                log.debug("fileName: {}", fileName);

                try {
                    file = yourCodeToMakeAFileFromInputStream(part.getContent(), fileName.get());
                }

                catch (IOException e) {
                    log.error("saveToFile: " + e.toString());
                    return Response.status(Status.INTERNAL_SERVER_ERROR).entity("Unable to save file").build();
                }
            }

            else {

                try {
                    String value = new String(part.getContent().readAllBytes(), StandardCharsets.UTF_8);
                    log.debug("part {}={}", partName, value);
                    params.put(partName, value);
                }

                catch (IOException e) {
                    String msg = "Invalid text value submitted for " + partName;
                    log.error("{}: {}", msg, e.toString());
                    return Response.status(Status.BAD_REQUEST).entity(msg).build();
                }
            }
        }

        if (file == null) {
            String msg = "No file parameter was submitted.";
            log.warn(msg);
            return Response.status(Status.BAD_REQUEST).entity(msg).build();
        }

        return yourCodeToProcessTheFileAndTextFields(file, params);
    }
  
    ...
}

Liberty server.xml

    <featureManager>
        <feature>restfulWS-3.1</feature>
    </featureManager>

Or use a feature that includes that, like webProfile-10.0.

References