{span:style=font-size:2em;font-weight:bold} JAX-RS : Understanding the Basics {span}

What is New in JAX-RS 2.0

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Either javax.ws.rs.core.Response or custom type can be returned. javax.ws.rs.core.Response can be used to set the HTTP response code, headers and entity. JAX-RS MessageBodyWriters (see below) are in charge of serializing the response entities, those which are returned directly or as part of javax.ws.rs.core.Response.

Response Streaming 

JAX-RS StreamingOutput

StreamingOutput can be used to stream the data to the client, for example:

@GET
@Path("/books/pdf")
@Produces("application/pdf")
public StreamingOutput getPdf() {
    return new StreamingOutput() {
        public void write(final OutputStream os) {
           // read chunks of data from PDF and write to OutputStream
        }  
    };
}

CXF StreamingResponse

CXF 3.0.0 introduces StreamingResponse extension. It can be used with the WebSocket transport or as a possible replacement for the code working with StreamingOutput.

For example, consider that a number of resources need to be returned as they become available:

@GET
@Path("/books")
@Produces("application/xml")
public StreamingResponse<Book> getBooks() {
    return new StreamingResponse<Book>() {
        public void writeTo(final Writer<Book> writer) {
           writer.getEntityStream().write("<Books>".getBytes());
           writer.write(new Book("CXF"));
           writer.write(new Book("JAX-RS"));
           writer.getEntityStream().write("</Books>".getBytes());
        }  
    };
}

Exception handling

One can either throw an unchecked WebApplicationException or return Response with a proper error code set.
The former option may be a better one when no JAX-RS types can be added to method signatures.

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