NIO Extension

Introduction

Servlet 3.1 API introduces a support for Non-Blocking IO, see this tutorial for more information.

The idea is that when the service code reads or writes the stream it does not block at all and only does a read or write action when a servlet container is ready to handle it effectively.

Early JAX-RS 2.1 API had a server-side prototype to help the JAX-RS service code utilize this Servlet 3.1 NIO features in a JAX-RS friendly way. Unfortunately that prototype was dropped from the final 2.1 API with the future major JAX-RS version expected to provide a much more complete and sophisticated NIO API.

CXF 3.2.0 has retained the implementation of the original JAX-RS 2.1 NIO API prototype and made it possible for the users to experiment with it.

NIO Read

@POST
@Consumes(MediaType.TEXT_PLAIN)
@Produces(MediaType.TEXT_PLAIN)
public void uploadBookStream(@Suspended AsyncResponse response) {
    final ByteArrayOutputStream out = new ByteArrayOutputStream();
    final byte[] buffer = new byte[4096];
    final LongAdder adder = new LongAdder();
 
    new NioReadEntity(
        // read handler                 
        in -> {
            final int n = in.read(buffer);
            if (n > 0) {
                adder.add(n);
                out.write(buffer, 0, n);
            }
        },
        // completion handler
        () -> {
            closeOutputStream(out);
            response.resume("Book Store uploaded: " + adder.longValue() + " bytes");
        }
        // by default the runtime will resume AsyncResponse with Throwable itself
        // if the error handler is not provided
         
        //,
        // error handler
        //t -> {
        //    response.resume(t);
        //}
    );
}

NIO Write

@GET
@Produces(MediaType.TEXT_PLAIN)
    public Response getBookStream() throws IOException {
        final ByteArrayInputStream in = new ByteArrayInputStream(
            IOUtils.readBytesFromStream(getClass().getResourceAsStream("/files/books.txt")));
 
        final byte[] buffer = new byte[4096];
 
        return Response.ok().entity(
 
                new NioWriteEntity(
         
                   out -> {
 
                    final int n = in.read(buffer);
                    if (n >= 0) {
                        out.write(buffer, 0, n);
                        return true;
                    }
                    closeInputStream(in);
                    return false;
                }
                // by default the runtime will throw the exception itself
                // if the error handler is not provided
                //,
                //throwable -> {
                //    throw throwable;
                //}
            ))
            .build();
    }

Even Easier NIO Write

 

import org.apache.cxf.annotations.UseNio;
@GET
@Produces(MediaType.TEXT_PLAIN)
@Path("/is")
@UseNio
public InputStream getBookStreamFromInputStream() throws IOException {
    return getClass().getResourceAsStream("/files/books.txt");
}