[HTTPCLIENT-1180] NullPointerException when using HttpHead and Request/Response interceptors

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.1.3
• Fix Version/s: 4.2 Final
• Component/s: HttpClient (classic)
• Labels: nullpointerexception
• Environment: Operating System: Windows 7 64 bit, Software Platform : JDK 1.7.0.2
• Assignee: Unassigned
• Reporter: Peter Joole
• Created: 02/Apr/12 21:58
• Updated: 05/Oct/13 19:41
• Resolved: 10/Apr/12 19:37

Description

When you try to execute a HttpHead object instead of a HttpGet object while using the add request/response interceptors, you get 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.

This is the error stack trace I get when executing the code 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