I am trying to use AsyncHttpClient in order to send multiple requests at once, add each response to a list, and then do some logic on the list once all responses have come back.
So far I have:
//I have a private static ArrayList<String> lists that I am hoping
//to use to concatenate all responses into one list with
private static ArrayList<String> lists;
/*
* @param bodies - an array list of the bodies I will be iterating through (as JSON strings) to add a different body to each post request
* @param url - the url to send post request to
*/
public void makeTheCalls(ArrayList<String> bodies, String url) {
AsyncHttpClient client = asyncHttpClient();
for (int idx = 0; idx < bodies.size(); idx++) {
client.preparePost(url).setBody(bodies.get(idx)).execute(new AsyncCompletionHandler<Void>() {
@Override
public Void onCompleted(Response response) throws exception {
// map the response to my POJO for this particular response
MyClass obj = objectMapper.readValue(response.getResponseBody(), MyClass.class);
//print the ArrayList<String> i want to concat to my master list
System.out.println(obj.getMyField());
lists.addAll(obj.getMyfield());
return null;
}
});
}
System.out.println(lists.size());
}
This seems to be making all of my post requests asynchronously and it is even printing each of my response correctly. But when I try to use the 'lists' field later on, like when I try to print lists.size(), it seems to be empty still.
Does this code correctly use a static field to allow each thread to edit the same instance? Is the logic with the 'lists' array happening before the responses are coming back? (if so how can i get the logic to delay until all requests have come back while keeping the calls asynchronous?
____________________ANSWER__________________
the application was making all the async requests, and then continuing before the responses were coming back. The use of a CountDownLatch solved this issue
//I have a private static ArrayList<String> lists that I am hoping
//to use to concatenate all responses into one list with
private static ArrayList<String> lists;
/*
* @param bodies - an array list of the bodies I will be iterating through (as JSON strings) to add a different body to each post request
* @param url - the url to send post request to
*/
public void makeTheCalls(ArrayList<String> bodies, String url) {
final CountDownLatch latch = new CountDownLatch(bodies.size());
AsyncHttpClient client = asyncHttpClient();
for (int idx = 0; idx < bodies.size(); idx++) {
client.preparePost(url).setBody(bodies.get(idx)).execute(new AsyncCompletionHandler<Void>() {
@Override
public Void onCompleted(Response response) throws exception {
// map the response to my POJO for this particular response
MyClass obj = objectMapper.readValue(response.getResponseBody(), MyClass.class);
//print the ArrayList<String> i want to concat to my master list
System.out.println(obj.getMyField());
lists.addAll(obj.getMyfield());
return null;
}
});
}
latch.await();
client.close();
System.out.println(lists.size());
}
