org.eclipse.jetty.proxy

Interface AsyncMiddleManServlet.ContentTransformer

All Known Implementing Classes:

AfterContentTransformer, AsyncMiddleManServlet.GZIPContentTransformer

Enclosing class:

AsyncMiddleManServlet

public static interface AsyncMiddleManServlet.ContentTransformer

Allows applications to transform upstream and downstream content.

Typical use cases of transformations are URL rewriting of HTML anchors (where the value of the href attribute of <a> elements is modified by the proxy), field renaming of JSON documents, etc.

Applications should override AsyncMiddleManServlet.newClientRequestContentTransformer(HttpServletRequest, Request) and/or AsyncMiddleManServlet.newServerResponseContentTransformer(HttpServletRequest, HttpServletResponse, Response) to provide the transformer implementation.

Field Summary

Fields

Modifier and Type	Field and Description
static AsyncMiddleManServlet.ContentTransformer	IDENTITY The identity transformer that does not perform any transformation.

Method Summary

Modifier and Type	Method and Description
void	transform(ByteBuffer input, boolean finished, List<ByteBuffer> output) Transforms the given input byte buffers into (possibly multiple) byte buffers.

Field Detail

IDENTITY

static final AsyncMiddleManServlet.ContentTransformer IDENTITY

The identity transformer that does not perform any transformation.

Method Detail

transform

void transform(ByteBuffer input,
               boolean finished,
               List<ByteBuffer> output)
        throws IOException

Transforms the given input byte buffers into (possibly multiple) byte buffers.

The transformation must happen synchronously in the context of a call to this method (it is not supported to perform the transformation in another thread spawned during the call to this method). The transformation may happen or not, depending on the transformer implementation. For example, a buffering transformer may buffer the input aside, and only perform the transformation when the whole input is provided (by looking at the finished flag).

The input buffer will be cleared and reused after the call to this method. Implementations that want to buffer aside the input (or part of it) must copy the input bytes that they want to buffer.

Typical implementations:

 // Identity transformation (no transformation, the input is copied to the output)
 public void transform(ByteBuffer input, boolean finished, List<ByteBuffer> output)
 {
     output.add(input);
 }

 // Discard transformation (all input is discarded)
 public void transform(ByteBuffer input, boolean finished, List<ByteBuffer> output)
 {
     // Empty
 }

 // Buffering identity transformation (all input is buffered aside until it is finished)
 public void transform(ByteBuffer input, boolean finished, List<ByteBuffer> output)
 {
     ByteBuffer copy = ByteBuffer.allocate(input.remaining());
     copy.put(input).flip();
     store(copy);

     if (finished)
     {
         List<ByteBuffer> copies = retrieve();
         output.addAll(copies);
     }
 }
 

Parameters:

input - the input content to transform (may be of length zero)

finished - whether the input content is finished or more will come

output - where to put the transformed output content

Throws:

IOException - in case of transformation failures