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From Oleg Kalnichevski <ol...@apache.org>
Subject Re: NullPointerException when using HttpHead and Request/Response interceptors
Date Mon, 02 Apr 2012 21:41:39 GMT
On Mon, 2012-04-02 at 22:24 +0200, Peter Joole wrote:
> Hi,
> 
> I have been using the HttpClient library for a couple of days now in my
> project. I use the ThreadSafeClientConnManager() to get all my resources
> and it works. I also use the example with the add request/response
> interceptor to try to get the resources gzipped. However when I tried to
> use a HttpHead instead of a HttpGet object I got a NullPointerException.
> 
> I can replicate the exception when using the ClientGZipContentCompression
> example that can be found at the HttpClient examples. But instead of using
> the HttpGet object I execute a HttpHead object. When I comment the
> interceptor parts out, I don't get the exception.
> 
> So I was wondering if this is a bug or not?
> 

This certainly looks like a bug. Please raise a JIRA for this issue.

Oleg

> This is the error stack trace I get when executing in netbeans:
> 
> Exception in thread "main" java.lang.NullPointerException
> at
> testhttphead.ClientGZipContentCompression$2.process(ClientGZipContentCompression.java:74)
> at
> org.apache.http.protocol.ImmutableHttpProcessor.process(ImmutableHttpProcessor.java:116)
> at
> org.apache.http.protocol.HttpRequestExecutor.postProcess(HttpRequestExecutor.java:342)
> at
> org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:472)
> at
> org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820)
> at
> org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:754)
> at
> org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:732)
> at
> testhttphead.ClientGZipContentCompression.main(ClientGZipContentCompression.java:92)
> Java Result: 1
> 
> Here is the code that gives me the error:
> 
> package testhttphead;
> 
> import java.io.IOException;
> import java.io.InputStream;
> import java.util.zip.GZIPInputStream;
> import org.apache.http.*;
> import org.apache.http.client.methods.HttpHead;
> import org.apache.http.entity.HttpEntityWrapper;
> import org.apache.http.impl.client.DefaultHttpClient;
> import org.apache.http.protocol.HttpContext;
> import org.apache.http.util.EntityUtils;
> 
> /**
>  * Demonstration of the use of protocol interceptors to transparently modify
>  * properties of HTTP messages sent / received by the HTTP client.
>  * <p/>
>  * In this particular case HTTP client is made capable of transparent
> content
>  * GZIP compression by adding two protocol interceptors: a request
> interceptor
>  * that adds 'Accept-Encoding: gzip' header to all outgoing requests and a
>  * response interceptor that automatically expands compressed response
> entities
>  * by wrapping them with a uncompressing decorator class. The use of
> protocol
>  * interceptors makes content compression completely transparent to the
> consumer
>  * of the {@link org.apache.http.client.HttpClient HttpClient} interface.
>  */
> public class ClientGZipContentCompression {
> 
>     public final static void main(String[] args) throws Exception {
>         DefaultHttpClient httpclient = new DefaultHttpClient();
> 
>         try {
>             httpclient.addRequestInterceptor(new HttpRequestInterceptor() {
> 
>                 public void process(
>                         final HttpRequest request,
>                         final HttpContext context) throws HttpException,
> IOException {
>                     if (!request.containsHeader("Accept-Encoding")) {
>                         request.addHeader("Accept-Encoding", "gzip");
>                     }
>                 }
>             });
> 
>             httpclient.addResponseInterceptor(new HttpResponseInterceptor()
> {
> 
>                 public void process(
>                         final HttpResponse response,
>                         final HttpContext context) throws HttpException,
> IOException {
>                     HttpEntity entity = response.getEntity();
>                     Header ceheader = entity.getContentEncoding();
>                     if (ceheader != null) {
>                         HeaderElement[] codecs = ceheader.getElements();
>                         for (int i = 0; i < codecs.length; i++) {
>                             if
> (codecs[i].getName().equalsIgnoreCase("gzip")) {
>                                 response.setEntity(
>                                         new
> GzipDecompressingEntity(response.getEntity()));
>                                 return;
>                             }
>                         }
>                     }
>                 }
>             });
> 
>             HttpHead httpHead = new HttpHead("http://www.howest.be");
> 
>             // Execute HTTP request
>             System.out.println("executing request " + httpHead.getURI());
>             HttpResponse response = httpclient.execute(httpHead);
> 
>             System.out.println("----------------------------------------");
>             System.out.println(response.getStatusLine());
>             System.out.println(response.getLastHeader("Content-Encoding"));
>             System.out.println(response.getLastHeader("Content-Length"));
>             System.out.println("----------------------------------------");
> 
>             HttpEntity entity = response.getEntity();
> 
>             if (entity != null) {
>                 String content = EntityUtils.toString(entity);
>                 System.out.println(content);
> 
> System.out.println("----------------------------------------");
>                 System.out.println("Uncompressed size: " +
> content.length());
>             }
> 
>         } finally {
>             // When HttpClient instance is no longer needed,
>             // shut down the connection manager to ensure
>             // immediate deallocation of all system resources
>             httpclient.getConnectionManager().shutdown();
>         }
>     }
> 
>     static class GzipDecompressingEntity extends HttpEntityWrapper {
> 
>         public GzipDecompressingEntity(final HttpEntity entity) {
>             super(entity);
>         }
> 
>         @Override
>         public InputStream getContent()
>                 throws IOException, IllegalStateException {
> 
>             // the wrapped entity's getContent() decides about repeatability
>             InputStream wrappedin = wrappedEntity.getContent();
> 
>             return new GZIPInputStream(wrappedin);
>         }
> 
>         @Override
>         public long getContentLength() {
>             // length of ungzipped content is not known
>             return -1;
>         }
>     }
> }
> 
> With kind regards,
> 
> Peter



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