JAX-RS Provider for deserializing

fruitcow · 01-09-2011 10:45am #1

I have a question regarding the use of Providers to serialize/deserialize data when using Rest within Java. I am using an example where I POST an image to a Rest service.

This is the Provider class. (To make it easier to read I've omitted all imports)

@Provider
@Consumes("image/jpeg")
class ImageProvider implements MessageBodyReader<Image> {

    @Override
    public Image readFrom(Class<Image> type,
            Type genericType,
            Annotation[] annotations,
            MediaType mediaType,
            MultivaluedMap<String, String> httpHeaders,
            InputStream entityStream) throws IOException,
            WebApplicationException {
        return ImageIO.read(entityStream);
    }

    @Override
    public boolean isReadable(Class<?> arg0, Type arg1, Annotation[] arg2,
            MediaType arg3) {
        // TODO Auto-generated method stub
        return false;
    }

}

This is the Rest class. (Again, imports omitted)

@Path ("/rsimage")
public class RSImage {
    
    @Path("/active")
    @GET
    @Produces("text/html")
    public String activeTest(){
        return "<html lang=\"en\"><body>active</body></html>";
    }
    
    @Path("jpeg")
    @Consumes("image/jpeg")
    @Produces("text/html")
    @POST
    public String printImageDimesions(Image image){        
        int imageWidth = image.getWidth(null);
        int imageHeight = image.getHeight(null);
        return "<html lang=\"en\"><body>width: [" + imageWidth + 
        "] height: [" + imageHeight + "]</body></html>";
    }
}

I confirm the service is running by calling the /active test method.

Can anyone tell me how I need to modify the class so that the printImageDimesions() method can access the ImageProvider class. I've been searching Google for ages and just can't find any examples of this in use.

lynchie · 01-09-2011 12:48pm

Why do you need to access the provider from your service? The provider is responsible for converting the input stream to an Image which it has given you in the printImageDimensions() method.

fruitcow · 01-09-2011 1:04pm

lynchie wrote: »

Why do you need to access the provider from your service? The provider is responsible for converting the input stream to an Image which it has given you in the printImageDimensions() method.

The problem I have is that the Provider is in no way linked to the service class. It's not referenced in any configuration files (web.xml, etc) and in it's current form does nothing, it's just a standalone class. I know it doesn't work as it is right now but I don't know how to get it to work.

What I am trying to figure out is how to get the RSImage class to make use of the ImageProvider class.

lynchie · 02-09-2011 10:12am

You have to register your provider class. How you do this depends on what you are using. I use jersey and it scans my packages for classes to the Provider annotation. Think resteasy does that too. I assume the others do it too.

Also, your provider returns false in the isReadable, so you are saying that the provider should never be used.

Use some debugging to prove that your providers isReadable method is being called.

fruitcow · 03-09-2011 11:29am

lynchie wrote: »

You have to register your provider class. How you do this depends on what you are using. I use jersey and it scans my packages for classes to the Provider annotation. Think resteasy does that too. I assume the others do it too.

Also, your provider returns false in the isReadable, so you are saying that the provider should never be used.

Use some debugging to prove that your providers isReadable method is being called.

I'm using glassfish to test but when it starts up for some reason it doesn't automatically register the providers even though it is configured to be jersey aware. For now I've configured the provider in the web.xml and it seems to be doing the trick. I'm not looking to see whuu

Thanks for pointing out the isReadable change. The code was automatically generated from eclipse and defaults to false.

Now I'm getting a 415 error code which is related to the media-type not being supported. When I fix this I'll post the code including the test case if anyone is interested.

JAX-RS Provider for deserializing

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