在Spring Java中同时调用多Web服务

Question

I have a list of 30 servers and I have to make a REST call to each server to get their status. Currently I iterating through list of server and sequentially calling each REST call against each server. So totally it takes around 30 seconds in total to get the response from each server before returning the result to JSP VIEW.

How can we improve this?

Answer 1

One option you could consider is the Java8 streams like:

public void check() {
    List<String> endPoints = Arrays.asList("http://www.google.com", "http://www.stackoverflow.com", "inexistent");
    {
        // this will execute the requests in parallel
        List<Boolean> collected = performCheckOverStream(endPoints.parallelStream());
        System.out.println(collected);
    }
    {
        // this will execute the requests in serial
        List<Boolean> collected = performCheckOverStream(endPoints.stream());
        System.out.println(collected);
    }

}

private List<Boolean> performCheckOverStream(Stream<String> stream) {
    List<Boolean> collected = stream.map(new Function<String, Boolean>() {
        @Override
        public Boolean apply(String t) {
            // do what you need here
        }
    }).collect(Collectors.toList());
    return collected;
}

Using Spring you could either use a @Async annotated method or even use the AsyncRestTemplate, in both cases you will receive a Future<?> . A nice introduction to @Async can be found here and to the AsyncRestTemplate here .

Answer 2

You can do it via ThreaPool like this , with Thread count as your API call count.

public void REST_Thread_executor(int Thread_count, ArrayList URLS) {
    ExecutorService executor = Executors.newFixedThreadPool(Thread_count);
    for (int i = 0; i < Thread_count; i++) {
        String URL = URLS.get(i).toString();
        Runnable worker = new MyRunnable(URL);
        executor.execute(worker);
    }
    executor.shutdown();
    while (!executor.isTerminated()) {

    }
}

public String restAPICALL(URL) {
    GET or POST or PUT or DELETE 
}

public static class MyRunnable implements Runnable {

    private final String URL;

    RESTThreadExecutor restThreadExecutor = new RESTThreadExecutor();

    MyRunnable(String URL) {
        this.URL = URL;
    }

    @Override
    public void run() {
        restThreadExecutor.restAPICALL(URL);
    }
}

Answer 3

You can use the CompletableFuture Interface from java 9. Or the enable on your app the @EnableAsync and on your method use the @Async that will return to you an interface Future. The both are asynchronous stream.