A simple standalone dispatcher servlet, for working in disappointing environments

DispatcherServlet.java

import java.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@SuppressWarnings("serial")
public abstract class DispatcherServlet extends GenericServlet{

	private static final String VIEW_SUFFIX = ".jsp";
	private static final String VIEW_PREFIX = "/WEB-INF/views/";


	@Override
	public void service(ServletRequest req, ServletResponse res)
			throws ServletException, IOException {
		
		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) res;
		try {
			handleReflectively(request, response);
		} catch (Exception e) {
			e.printStackTrace();
			
			PrintWriter writer = response.getWriter();
			writer.write( "<pre>" );
			e.printStackTrace(writer);
			writer.write("</pre>");
			response.setStatus( HttpServletResponse.SC_INTERNAL_SERVER_ERROR );
			response.flushBuffer();
		}
	}

	private void handleReflectively(HttpServletRequest request, HttpServletResponse response) throws Exception{
		String uri = request.getRequestURI();
		uri = uri.substring(1, uri.length());
		if( uri.contains("/") ){
			throw new IllegalStateException("Unable to handle anything but root requests");
		}else if( uri.isEmpty() ){
			uri = "index";
		}
		
		Method method = getClass().getDeclaredMethod(uri, Model.class);
		Model model = new Model();
		Object viewObject = method.invoke(this, model);
		
		if(viewObject instanceof String == false){
			throw new IllegalStateException("Right now we only support returning strings for views...");
		}
		
		String view = (String) viewObject;
		Map<String, Object> map = model.getMap();
		request.setAttribute("it", map);
		request.getRequestDispatcher(VIEW_PREFIX + view + VIEW_SUFFIX).forward(request, response);
	}
	
	public static class Model{
		private Map<String, Object> map = new HashMap<String, Object>();
		
		public Model put(String key, Object value){
			map.put(key, value);
			return this;
		}
		
		private Map<String, Object> getMap(){
			return map;
		}
	}
	
	

}

ImplServlet.java

@SuppressWarnings("serial")
public class ImplServlet extends DispatcherServlet{
  
  	// will try to resolve /WEB-INF/views/test.jsp, with ${it.dummy} returning "Hello Worldddd"
	public String index(Model model){
		model.put("dummy", "Hello Worldddd");
		return "test";
		
	}

}