Source:
<code>protected void service(HttpServletRequest servletRequest, HttpServletResponse servletResponse) throws ServletException, IOException { if (servletRequest.getAttribute(ATTR_TARGET_URI) == null) { servletRequest.setAttribute(ATTR_TARGET_URI, targetUri); } if (servletRequest.getAttribute(ATTR_TARGET_HOST) == null) { servletRequest.setAttribute(ATTR_TARGET_HOST, targetHost); } String method = servletRequest.getMethod(); String proxyRequestUri = rewriteUrlFromRequest(servletRequest); HttpRequest proxyRequest; if (servletRequest.getHeader(HttpHeaders.CONTENT_LENGTH) != null || servletRequest.getHeader(HttpHeaders.TRANSFER_ENCODING) != null) { proxyRequest = newProxyRequestWithEntity(method, proxyRequestUri, servletRequest); } else { proxyRequest = new BasicHttpRequest(method, proxyRequestUri); } <START> if (!preProxyRequest(servletRequest, servletResponse, proxyRequest)) { <END> return; } copyRequestHeaders(servletRequest, proxyRequest); setXForwardedForHeader(servletRequest, proxyRequest); HttpResponse proxyResponse = null; try { if (doLog) { log("proxy " + method + " uri: " + servletRequest.getRequestURI() + " -- " + proxyRequest.getRequestLine().getUri()); } proxyResponse = proxyClient.execute(getTargetHost(servletRequest), proxyRequest); int statusCode = proxyResponse.getStatusLine().getStatusCode(); servletResponse.setStatus(statusCode, proxyResponse.getStatusLine().getReasonPhrase()); copyResponseHeaders(proxyResponse, servletRequest, servletResponse); if (statusCode == HttpServletResponse.SC_NOT_MODIFIED) { servletResponse.setIntHeader(HttpHeaders.CONTENT_LENGTH, 0); } else { copyResponseEntity(proxyResponse, servletResponse, proxyRequest, servletRequest); } } catch (Exception e) { if (proxyRequest instanceof AbortableHttpRequest) { AbortableHttpRequest abortableHttpRequest = (AbortableHttpRequest) proxyRequest; abortableHttpRequest.abort(); } if (e instanceof RuntimeException) throw (RuntimeException)e; if (e instanceof ServletException) throw (ServletException)e; if (e instanceof IOException) throw (IOException) e; throw new RuntimeException(e); } finally { if (proxyResponse != null) consumeQuietly(proxyResponse.getEntity()); } }</code><technical_language>Personally I name this function shouldProxyRequest() clearer asking subclass if is handle request if ProxyServlet proxy</technical_language>

Target:
protected void service(HttpServletRequest servletRequest, HttpServletResponse servletResponse) throws ServletException, IOException { if (servletRequest.getAttribute(ATTR_TARGET_URI) == null) { servletRequest.setAttribute(ATTR_TARGET_URI, targetUri); } if (servletRequest.getAttribute(ATTR_TARGET_HOST) == null) { servletRequest.setAttribute(ATTR_TARGET_HOST, targetHost); } String method = servletRequest.getMethod(); String proxyRequestUri = rewriteUrlFromRequest(servletRequest); HttpRequest proxyRequest; if (servletRequest.getHeader(HttpHeaders.CONTENT_LENGTH) != null || servletRequest.getHeader(HttpHeaders.TRANSFER_ENCODING) != null) { proxyRequest = newProxyRequestWithEntity(method, proxyRequestUri, servletRequest); } else { proxyRequest = new BasicHttpRequest(method, proxyRequestUri); } if (!shouldProxyRequest(servletRequest, servletResponse, proxyRequest)) { return; } copyRequestHeaders(servletRequest, proxyRequest); setXForwardedForHeader(servletRequest, proxyRequest); HttpResponse proxyResponse = null; try { if (doLog) { log("proxy " + method + " uri: " + servletRequest.getRequestURI() + " -- " + proxyRequest.getRequestLine().getUri()); } proxyResponse = proxyClient.execute(getTargetHost(servletRequest), proxyRequest); int statusCode = proxyResponse.getStatusLine().getStatusCode(); servletResponse.setStatus(statusCode, proxyResponse.getStatusLine().getReasonPhrase()); copyResponseHeaders(proxyResponse, servletRequest, servletResponse); if (statusCode == HttpServletResponse.SC_NOT_MODIFIED) { servletResponse.setIntHeader(HttpHeaders.CONTENT_LENGTH, 0); } else { copyResponseEntity(proxyResponse, servletResponse, proxyRequest, servletRequest); } } catch (Exception e) { if (proxyRequest instanceof AbortableHttpRequest) { AbortableHttpRequest abortableHttpRequest = (AbortableHttpRequest) proxyRequest; abortableHttpRequest.abort(); } if (e instanceof RuntimeException) throw (RuntimeException)e; if (e instanceof ServletException) throw (ServletException)e; if (e instanceof IOException) throw (IOException) e; throw new RuntimeException(e); } finally { if (proxyResponse != null) consumeQuietly(proxyResponse.getEntity()); } }