CODEWITHSUNDEEP
javaapache-httpclient-4.xapache-commons-httpclient
PKM
PKM

Reputation: 329

How to cache the httpclient object in Java?

Using Apache HttpClient 4.5.x in my client webapp which connects to (and log in to) another (say main) server webapp.

The relationship between these 2 webapps is many to many - meaning for some user's request in client webapp, it has to login as another user + make rest call, in the server webapp. So some separation of cookiestores is needed and there's no way (is there?) to get/set the cookie store after creating a httpclient instance, so each request thread received in client webapp does something like this (and need to optimize):

HttpClient client = HttpClientBuilder.create().setDefaultCookieStore(new BasicCookieStore()).build();
//Now POST to login end point and get back JSESSIONID cookie and then make one REST call, and then the client object goes out of scope when the request ends.

I was hoping to ask on the best practice of caching the httpclient instance object as its heavy and is supposed to be reused for at least multiple requests, if not for the whole client webapp as a static singleton.

Specifically, I was hoping for advice on which of these (if any) approaches would constitute a best practice:

  1. Use a static ConcurrentHashMap to cache the httpclient and its associated basiccookiestore for each "user" in client webapp, and to login only when the contained cached cookie is near to its expiry time. Not sure about memory usage, and un/rarely-used httpclient stay in memory without eviction.

  2. Cache only the Cookie (somehow), but recreate a new httpclient object whenever the need arises to use that cookie for a rest call. This saves the prior call to login until the cookie expires, but no reuse of htptclient.

  3. PooledConnectionManager - but can't find examples easily, though might require devising an eviction strategy, max number of threads etc. (so can be complex).

Is there any better way of doing this ? Thanks.

References:

Generally it is recommended to have a single instance of HttpClient per communication component or even per application

Upvotes: 1

Views: 3272

Answers (2)

ok2c
ok2c

Reputation: 27528

Why would you want to do all this? One can assign a different CookieStore on a per request basis by using a local HttpContext.

If needed one can maintain a map of CookieStore instances per unique user.

CloseableHttpClient httpclient = HttpClients.createDefault();
CookieStore cookieStore = new BasicCookieStore();

// Create local HTTP context
HttpClientContext localContext = HttpClientContext.create();
// Bind custom cookie store to the local context
localContext.setCookieStore(cookieStore);

HttpGet httpget = new HttpGet("http://httpbin.org/cookies");
System.out.println("Executing request " + httpget.getRequestLine());

// Pass local context as a parameter
CloseableHttpResponse response = httpclient.execute(httpget, localContext);
try {
    System.out.println("----------------------------------------");
    System.out.println(response.getStatusLine());
    List<Cookie> cookies = cookieStore.getCookies();
    for (int i = 0; i < cookies.size(); i++) {
        System.out.println("Local cookie: " + cookies.get(i));
    }
    EntityUtils.consume(response.getEntity());
} finally {
    response.close();
}

Upvotes: 1

sweet suman
sweet suman

Reputation: 1082

Using concurrent hash map would be the simplest way to achieve what you want to do.

Additionally, if you are using Spring, you might want to create a bean for holding the HTTP client.

Upvotes: 2

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