CODEWITHSUNDEEP
restspring-mvcasynchronousstreamstreaming
user2018726
user2018726

Reputation: 688

Stream a response in Spring mvc

This is the situation, lets say i have and endpoint and receive a request that retrieves data between a range of time or whatever, and the result of that request is a big list that i get from a database, lets say a list of a "Person" object, then for each of this person objects I have to call another method that it may be a little slow and it would delay the response a lot if i have to wait until it is executed for all the elements of this big list.

What i would like to accomplish is that i can stream the response through a rest endpoint and my front end does not have to wait until all this list is processed to start displaying it on the screen.

So i have a confusion here, i know that an asynchronous method using spring @Async it would make the consumer to be able to give a response even if the task is still not finished, but as far as i understand, this is helpful in the case of sending emails, or any other task or series of tasks whose response you are not going to display in the screen.

But in the case of a response that is meant to be displayed in the screen, i guess i should stream a chunk of data as soon as i have a whole "person" object ready.

What is the right way to accomplish this? is the Async method of any help in this situation or i should only find a way to detect when i have a person object is formed to stream it? or i'm terribly wrong and im not understanding the concepts of Async and streaming.

A little example would help.

Thanks.

Upvotes: 1

Views: 1630

Answers (1)

Karthik N G
Karthik N G

Reputation: 11

I have been trying to understand the same concept from last 3 days and here is the my understanding which may help you.

Asynchronous REST endpoint:

If your REST end point is doing some complex business logic or calling some external service and may take some time respond back, its better to respond back from API ASAP moving the time consuming logic to background (separate thread). This is where Asynchronous processing will help.

Chunked output:

If your end point is expected to send large amount of data. In order to improve the user experience if i decide to start rendering the output (in UI) as soon as they start becoming available, chunked output from REST end point is the better approach.

Using jersey we can achieve both asynchronous processing and chunked output as mentioned in the below sample.

public ChunkedOutput<String> getChunkedResponse() {
        final ChunkedOutput<String> output = new ChunkedOutput<String>(String.class);

        new Thread() {
            public void run() {
                try {
                    String chunk;
                    int index = 0;

                    while ((chunk = getWordAtIndex(index)) != null) {
                        output.write(chunk);
                        index++;
                    }
                } catch (IOException e) {
                    //Add code to handle the IO Exception during this operation
                } finally {
                    try {
                        output.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();

        return output; // This output object may be returned way before output is created
    }

I have tried out a sample to test this out with jersey and spring-boot combination. You can check it out in my git repository here.

Hope it helps.

Upvotes: 1

Related Questions