HttpClient 4 0 1 - how to release connection

Question

I have a loop over a bunch of URLs  for each one I m doing the following   private String doQuery String url       HttpGet httpGet   new HttpGet url     setDefaultHeaders httpGet      static method   HttpResponse response   httpClient execute httpGet        httpClient instantiated in constructor    int rc   response getStatusLine   getStatusCode       if  rc    200           some stuff        return         HttpEntity entity   response getEntity       if  entity    null           some stuff        return            process the entity  get input stream etc      The first query is fine  the second throws this exception      Exception in thread  main    java lang IllegalStateException    Invalid use of   SingleClientConnManager  connection   still allocated  Make sure to release   the connection before allocating   another one   at   org apache http impl conn SingleClientConnManager getConnection SingleClientConnManager java 199      at   org apache http impl conn SingleClientConnManager 1 getConnection SingleClientConnManager java 173          This is just a simple single-threaded app  How can I release this connection

User · Answer

If you want to re-use the connection then you must consume content stream completely after every use as follows :

EntityUtils.consume(response.getEntity())

Note : you need to consume the content stream even if the status code is not 200. Not doing so will raise the following on next use :

Exception in thread "main" java.lang.IllegalStateException: Invalid use of SingleClientConnManager: connection still allocated. Make sure to release the connection before allocating another one.

If it's a one time use, then simply closing the connection will release all the resources associated with it.

User · Answer

I m chiming in with a detailed answer that specifically addresses Apache HttpClient 4 0 1   I m using this HttpClient version  since it s provided by WAS v8 0  and I need to use that provided HttpClient within Apache Wink v1 1 1  also provided by WAS v8 0  to make some NTLM-authenticated REST calls to Sharepoint   To quote Oleg Kalnichevski on the Apache HttpClient mailing list      Pretty much all this code is not necessary   1  HttpClient will    automatically release the underlying connection as long as the entity    content is consumed to the end of stream   2  HttpClient will    automatically release the underlying connection on any I O exception    thrown while reading the response content  No special processing is    required in such as case       In fact  this is perfectly sufficient to ensure proper release of resources   HttpResponse rsp   httpclient execute target  req    HttpEntity entity   rsp getEntity     if  entity    null         InputStream instream   entity getContent         try               process content        finally            instream close                entity consumeContent   would also do                 That is it    Source

User · Answer

HTTP HEAD requests must be treated slightly differently because response getEntity   is null  Instead  you must capture the HttpContext passed into HttpClient execute   and retrieve the connection parameter to close it  in HttpComponents 4 1 X anyway    HttpRequest httpRqst   new HttpHead  uri    HttpContext httpContext   httpFactory createContext    HttpResponse httpResp   httpClient execute  httpRqst  httpContext             Close when finished HttpEntity entity   httpResp getEntity    if  null    entity        Handles standard  GET  case   EntityUtils consume  entity    else     ConnectionReleaseTrigger  conn          ConnectionReleaseTrigger  httpContext getAttribute  ExecutionContext HTTP CONNECTION         Handles  HEAD  where entity is not returned   if  null    conn       conn releaseConnection        HttpComponents 4 2 X added a releaseConnection   to HttpRequestBase to make this easier

User · Answer

I ve got this problem when I use HttpClient in Multithread envirnoment  Servlets    One servlet still holds connection and another one want to get connection    Solution    version 4 0 use ThreadSafeClientConnManager  version 4 2 use PoolingClientConnectionManager  and set this two setters    setDefaultMaxPerRoute setMaxTotal

User · Answer

I m using HttpClient 4 5 3  using CloseableHttpResponse close worked for me      CloseableHttpResponse response   client execute request        try           HttpEntity entity   response getEntity            String body   EntityUtils toString entity           checkResult body           EntityUtils consume entity         finally           response close           With Java7 and beyond  try  CloseableHttpResponse response   client execute request

User · Answer

If the response is not to be consumed  then the request can be aborted using the code below      Low level resources should be released before initiating a new request HttpEntity entity   response getEntity     if  entity    null           Do not need the rest     httpPost abort        Reference  http   hc apache org httpcomponents-client-ga tutorial html fundamentals html d5e143  Apache HttpClient Version  4 1 3

User · Answer

This seems to work great          if  response getEntity      null              response getEntity   consumeContent             if   And don t forget to consume the entity even if you didn t open its content  For instance  you expect a HTTP OK status from the response and don t get it  you still have to consume the entity

User · Answer

To answer my own question  to release the connection  and any other resources associated with the request  you must close the InputStream returned by the HttpEntity   InputStream is   entity getContent          process the input stream       is close             releases all resources   From the docs

User · Answer

The recommended way  by Httpcomponents 4 1  is to close connection and release any underlying resources   EntityUtils consume HttpEntity    where HttpEntity passed is a response entity

User · Answer

I had the same issue and solved it by closing the response at the end of the method   try          make the request and get the entity    catch final Exception e           handle the exception   finally       if response    null            response close

User · Answer

Since version 4 2  they introduced a much more convenience method that simplifies connection release  HttpRequestBase releaseConnection

User · Answer

Highly recommend using a handler to handle the response   client execute yourRequest defaultHanler     It will release the connection automatically with consume HTTPENTITY  method   A handler example   private ResponseHandler lt String gt  defaultHandler   new ResponseHandler lt String gt           Override     public String handleResponse HttpResponse response          throws IOException           int status   response getStatusLine   getStatusCode             if  status  gt   200  amp  amp  status  lt  300                HttpEntity entity   response getEntity                return entity    null   EntityUtils toString entity    null            else               throw new ClientProtocolException  Unexpected response status      status

[java] HttpClient 4.0.1 - how to release connection?

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