6.3 Input and Output Stream Adapters

Input and Output Stream Adapters

The Apache Wink Client provides the ability to manipulate raw Http input and output entity streams through the InputStreamAdapter and the OutputStreamAdapter interfaces. This is useful for modifying the input and output streams, regardless of the actual entity, for example when adding compression capabilities.
The adapt() method of the output stream adapter is called before the request headers are committed, in order to allow the adapter to manipulate them.

The adapt() method of the input stream adapter is called after the response status code and the headers are received in order to allow the adapter to behave accordingly.

Stream Adapters Example

The following example demonstrates how to implement input and output adapters.

Gzip Handler

The following code snippet is an example of adding a input and output adapters in the Gzip handler.

public class GzipHandler implements ClientHandler {
   public ClientResponse handle(ClientRequest request,
                                HandlerContext context) {
        request.getHeaders().add("Accept-Encoding", "gzip");
        context.addInputStreamAdapter(new GzipInputAdapter());
        context.addOutputStreamAdapter(new GzipOutputAdapter());
        return context.doChain(request);
  }}

Explanation

The Gzip handler creates instances of the GzipInputAdapter and the GzipOutputAdapter and adds them to the stream adapters of the current request by invoking the addInputStreamAdapter() method and the addOutputStreamAdapter() method on the HandlerContext instance.

Gzip Input Stream Adapter

The following code snippet is an example of an implementation of a Gzip input stream adapter.

class GzipInputAdapter implements InputStreamAdapter{
        public InputStream adapt(InputStream is,
                                 ClientResponse response) {
      String header = response.getHeaders().getFirst("Content-Encoding");
      if (header != null && header.equalsIgnoreCase("gzip")) {
        return new GZIPInputStream(is);
      }
      return is;
   }}

Explanation

The Gzip input stream adapter is responsible for wrapping the input stream with the Gzip input stream.

Gzip Output Stream Adapter

The following code snippet is an example of an implementation of a Gzip output stream adapter.

class GzipOutputAdapter implements OutputStreamAdapter {
    public OutputStream adapt(OutputStream os,
                              ClientRequest request) {
        request.getHeaders().add("Content-Encoding", "gzip");
        return new GZIPOutputStream(os);
    }}

Explanation

The Gzip output stream adapter is responsible for wrapping the output stream with the Gzip output stream.