Properly Releasing Resources with Apache HttpClient 4.5: Best Practices

Update: releaseConnection() is no longer recommended in HttpClient 4.5; the library now uses PoolingHttpClientConnectionManager for connection pool management.

When a request fails and the CloseableHttpResponse is null, perform a null‑check before attempting to close it. Below is a new utility method that safely extracts the response entity as a string.

/**
 * Get response content from CloseableHttpResponse
 * @param response the HTTP response
 * @return response body as String
 */
private static String getContent(CloseableHttpResponse response) {
    HttpEntity entity = response.getEntity(); // obtain response entity
    String content = EMPTY;
    try {
        content = EntityUtils.toString(entity, UTF_8); // convert entity to string
        EntityUtils.consume(entity); // consume entity and release resources
        if (response != null) response.close();
    } catch (ParseException e1) {
        output("Error parsing response entity!", e1);
    } catch (IOException e1) {
        output("IO exception while parsing response entity!", e1);
    }
    return content;
}

To close a response safely, create the response object, perform any intermediate processing, then call response.close() inside a try‑catch block to handle possible IOException.

CloseableHttpResponse response = null; // create response object
// ... do some work ...
try {
    response.close();
} catch (IOException e2) {
    output("Failed to close response!", e2);
}

Only close the response after you have determined the response length; otherwise you must consume the stream using EntityUtils.consume() or use the deprecated abort() method. The recommended way to consume the entity is via HttpEntity#getContent() or HttpEntity#writeTo(OutputStream).

Releasing the connection after a request is straightforward: call request.releaseConnection();. Whether the connection can be reused depends on the connection pool and manager configuration, which is beyond the scope of this article.

Finally, always close the HttpClient instance when all work is done to free system resources.

protected static CloseableHttpClient httpClient = getCloseableHttpClients();
// ... do some work ...
httpClient.close();