如何在Google App Engine HTTP响应中包括图形和表格

Question

I am building an application where audio data is uploaded to my GAE server, processed, and displayed as a response to an HTTP GET request.

Part of the data I wish to display is in the format of a graph. What I am having a hard time understanding is how to create my response in such a way that I can include graphs.

From what I understand, one approach might be to create the graph using this API: http://googleappsdeveloper.blogspot.ca/2011/09/visualize-your-data-charts-in-google.html And then store it as a blob in my datastore. I can then create a JSP to serve the blob as an image? Not sure if I am understanding this correctly. Specifically, I'm not sure about being able to access all of this functionality from GAE, and if I'm doing this in a convoluted way.

I am quite new to GAE and web programming in general, so I greatly appreciate feedback and suggestions on how to do this in the simplest/quickest way. I wouldn't mind links to relevant resources as well.

Answer 1

you have mainly two ways to go:
1) Send in your response only data and let your front end (your website or app) parse them and put them in graph form. You can write in your response the data to show, and it is quite suggested to give them a structure (so as your front-end can easily interpret and validate the data). Common formats are JSON and XML (they basically can give a custom hierarchical structure to your data,for example you can organize the graph data in columns form)
The way to build a graph depends on the technology you use in your front-end and you can either use a third part library or build your own

2) Create graphs in your web application, store them and allow users to get them via HTTP. Once you have found a way to build a graph image from data you need to store it. GAE gives to you two storage systems, the Blobstore and the Google Cloud Storage.
I think You can save files in the Blobstore only by direct upload via HTTP therefore if you're saving image directly in your GAE web app there's no easy way to use it (you should open an HTTP connection).
The Google cloud storage instead can be accessed by using the dedicated libraries ( https://developers.google.com/appengine/docs/java/googlecloudstorageclient/getstarted ) that you need to download and add to your project during the developing phase (and activate them) there are tutorials for this ( https://developers.google.com/appengine/docs/java/googlecloudstorageclient/ ).

In order to serve images you can bypass the middle code that should read the image from the GCS and serve it as a response by using the Images service. Once generated a so called "serving URL" associated to a given image, the images service permits to directly access to the image via HTTP ( https://developers.google.com/appengine/docs/java/images/ ).

Finally the first option is interesting because (obviously if you can) it's simpler and lighter for the server side (the one you pay) and you can anyway cache the images to avoid useless computation, the second is maybe more correct in a certain point of view but it is more complex.