get contents of processed JSP into spring controller without using HttpClient?

Question

So normally in a Spring controller you'd just return a ModelAndView object and forward the request to the JSP.

What I need to do is actually get the contents of that processed JSP so I can then send it in a JSONP response (ex: callback("processed HTML from JSP");)

I know I could just use HttpClient to get the contents but was wondering if there's a way to avoid that extra step by calling something like:

String contents = processJSP(modelAndView);

Updated for geek to show my final solution:

First you need a fake HttpResponse to hold the response:

@Service
public class SpringUtils {
    private static final Logger LOG = Logger.getLogger(SpringUtils.class);

    @Autowired private ViewResolver viewResolver;
    @Autowired private LocaleResolver localeResolver;

    public String renderView(HttpServletRequest request, ModelAndView mav) {
        try {
            View view = viewResolver.resolveViewName(mav.getViewName(), localeResolver.resolveLocale(request));
            HttpServletResponse localResponse = new MyHttpServletResponseWrapper(new DummyResponse());

            view.render(mav.getModel(), request, localResponse);

            return localResponse.toString();
        } catch (Exception e) {
            return "";
        }
    }

    public boolean doesViewExist(HttpServletRequest request, String viewName) {
        try {
            if (viewResolver.resolveViewName(viewName, localeResolver.resolveLocale(request)) != null) {
                return true;
            }
        } catch (Exception e) {
            LOG.error(e.getMessage(), e);
        }

        return false;
    }

    static class MyHttpServletResponseWrapper extends HttpServletResponseWrapper {
        private StringWriter sw = new StringWriter();

        public MyHttpServletResponseWrapper(HttpServletResponse response) {
            super(response);
        }

        public PrintWriter getWriter() throws IOException {
            return new PrintWriter(sw);
        }

        public ServletOutputStream getOutputStream() throws IOException {
            throw new UnsupportedOperationException();
        }

        public String toString() {
            return sw.toString();
        }
    }
}

DummyResponse

public class DummyResponse implements HttpServletResponse {
    public DummyResponse() {
    }

    public void setAppCommitted(boolean appCommitted) {}
    public boolean isAppCommitted() { return false; }
    public int getContentCount() { return -1; }
    public boolean getIncluded() { return false; }
    public void setIncluded(boolean included) {}
    public String getInfo() { return null; }
    public ServletResponse getResponse() { return null; }
    public OutputStream getStream() { return null; }
    public void setStream(OutputStream stream) {}
    public void setSuspended(boolean suspended) {}
    public boolean isSuspended() { return false; }
    public void setError() {}
    public boolean isError() { return false; }
    public ServletOutputStream createOutputStream() throws IOException {
        return null;
    }
    public void finishResponse() throws IOException {}
    public int getContentLength() { return -1; }
    public String getContentType() { return null; }
    public PrintWriter getReporter() { return null; }
    public void recycle() {}
    public void write(int b) throws IOException {}
    public void write(byte b[]) throws IOException {}
    public void write(byte b[], int off, int len) throws IOException {}
    public void flushBuffer() throws IOException {}
    public int getBufferSize() { return -1; }
    public String getCharacterEncoding() { return null; }
    public void setCharacterEncoding(String charEncoding) {}
    public ServletOutputStream getOutputStream() throws IOException {
        return null;
    }
    public Locale getLocale() { return null; }
    public PrintWriter getWriter() throws IOException { return null; }
    public boolean isCommitted() { return false; }
    public void reset() {}
    public void resetBuffer() {}
    public void setBufferSize(int size) {}
    public void setContentLength(int length) {}
    public void setContentType(String type) {}
    public void setLocale(Locale locale) {}

    public Cookie[] getCookies() { return null; }
    public String getHeader(String name) { return null; }
    public Collection<String> getHeaders(String arg0) { return null; }
    public Collection<String> getHeaderNames() { return null; };
    public String[] getHeaderValues(String name) { return null; }
    public String getMessage() { return null; }
    public int getStatus() { return -1; }
    public void reset(int status, String message) {}
    public void addCookie(Cookie cookie) {}
    public void addDateHeader(String name, long value) {}
    public void addHeader(String name, String value) {}
    public void addIntHeader(String name, int value) {}
    public boolean containsHeader(String name) { return false; }
    public String encodeRedirectURL(String url) { return null; }
    public String encodeRedirectUrl(String url) { return null; }
    public String encodeURL(String url) { return null; }
    public String encodeUrl(String url) { return null; }
    public void sendAcknowledgement() throws IOException {}
    public void sendError(int status) throws IOException {}
    public void sendError(int status, String message) throws IOException {}
    public void sendRedirect(String location) throws IOException {}
    public void setDateHeader(String name, long value) {}
    public void setHeader(String name, String value) {}
    public void setIntHeader(String name, int value) {}
    public void setStatus(int status) {}
    public void setStatus(int status, String message) {}
}

Answer 1

Probably not possible easy way. Maybe injecting view resolver into controller and calling render with special response will help, but not sure :

ViewResolver viewResoler = // injected
View view = viewReslover.resolveViewName(String viewName, Locale locale);
HttpServletResponse xresponse = // custom response, buffers data
view.render(Map model, HttpServletRequest request, HttpServletResponse xresponse);
String content = // extract conten from data from xresponse 

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