Get the HTML markup for a resource in AEM / CQ.

AemResourceResolutionServlet.java

package com.nateyolles.aem;

import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.sling.SlingServlet;

import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.apache.sling.engine.SlingRequestProcessor;

import com.day.cq.contentsync.handler.util.RequestResponseFactory;
import com.day.cq.wcm.api.WCMMode;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

@SlingServlet(paths={"/bin/foo"})
public class AemResourceResolutionServlet extends SlingSafeMethodsServlet {

    /** Service to create HTTP Servlet requests and responses */
    @Reference
    private RequestResponseFactory requestResponseFactory;

    /** Service to process requests through Sling */
    @Reference
    private SlingRequestProcessor requestProcessor;

    @Override
    protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response) throws ServletException, IOException {

        /* The resource path to resolve. Use any selectors or extension. */
        String requestPath = "/content/myapp/us/en/index/jcr:content/myparsys/mycomponent_f93d.html";

        /* Setup request */
        HttpServletRequest req = requestResponseFactory.createRequest("GET", requestPath);
        WCMMode.DISABLED.toRequest(req);

        /* Setup response */
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        HttpServletResponse resp = requestResponseFactory.createResponse(out);

        /* Process request through Sling */
        requestProcessor.processRequest(req, resp, request.getResourceResolver());
        String html = out.toString();
    }
}

I'm working on something very similar for generating page preview without using ContentSync. The idea works as long as the resources are not clientlibs. See my fork.
Any ideas ?

I got around the issue by using HTMLLibraryManager to write the includes, but hoping to see a better way of doing that.

resp.getWriter().flush(); should be used

com.day.cq.contentsync.handler.util.RequestResponseFactory; is deprecated.
what is the alternative for this API ?