这里我使用 apache 的 HttpClient 库编写这个小程序。例如以下例。我们通过向 http://locahost:8080/codeschool/ 发送GET请求来得到server返回的HTML代码：

/*** 向localhost:8080发送GET请求，获取返回的HTML代码并保存到文件里* @author whf**/
public class Client {public static void main(String[] args) throws Exception {CloseableHttpClient httpclient = HttpClients.createDefault();try {HttpGet httpGet = new HttpGet("http://127.0.0.1:8080/codeschool");CloseableHttpResponse response = httpclient.execute(httpGet);try {System.out.println(response.getStatusLine());HttpEntity entity = response.getEntity();// entity封装了server返回的数据String html =  EntityUtils.toString(entity);// 将HTML代码写入到文件里saveContent(html, "/home/whf/workspace-sts/codeschool/home.html");EntityUtils.consume(entity);} finally {response.close();}} finally {httpclient.close();}}/*** 将HTML写入到指定文件里* * @param html* @param path 文件路径* @throws IOException*/private static void saveContent(String html, String path) throws IOException {FileOutputStream fos = new FileOutputStream(path);BufferedOutputStream bos = new BufferedOutputStream(fos);bos.write(html.getBytes());bos.close();}}

所需的 dependency 例如以下：

<dependencies><dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpclient</artifactId><version>4.3.4</version></dependency></dependencies>

运行一下该程序，就会得到 home.html 文件。

编写一个 url-pattern 为 /* 的 Filter 过滤器，一旦发现用户訪问的是主页，则直接返回上面生成的 home.html 文件，关闭输出流。代码例如以下：

public class SecureFilter implements Filter {private static final Logger logger = LoggerFactory.getLogger(SecureFilter.class);private ServletContext ctx;@Overridepublic void destroy() {}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {// 防止中文乱码request.setCharacterEncoding("UTF-8");HttpServletRequest req = (HttpServletRequest) request;String path = req.getRequestURI();// 请求的是资源。跳过if (true == path.startsWith("/codeschool/resources")) {chain.doFilter(request, response);return;}// 用户未登陆// 用户訪问主页// 返回静态页面if (path.equals("/codeschool/") || path.equals("/")) {writeStaticHomePage(req, (HttpServletResponse) response);return;}chain.doFilter(request, response);}/*** 将静态主页返回给client* * @param req* @param resp* @throws IOException*/private void writeStaticHomePage(HttpServletRequest req,HttpServletResponse resp) throws IOException {// 返回静态化页面// 得到home.html路径String pagePath = (String) ctx.getInitParameter("HOME_PAGE_PATH");if (logger.isDebugEnabled()) {logger.debug("主页静态页面路径:{}", pagePath);}// 将homt.html返回给clientServletOutputStream out = resp.getOutputStream();FileInputStream pageInStream = new FileInputStream(pagePath);BufferedInputStream bufInStream = new BufferedInputStream(pageInStream);byte[] buf = new byte[2048];int len = 0;while ((len = bufInStream.read(buf)) != -1) {out.write(buf, 0, len);}bufInStream.close();out.close();}@Overridepublic void init(FilterConfig cfg) throws ServletException {this.ctx = cfg.getServletContext();}}

能够在web.xml里配置 home.html 的路径：

<!-- 静态主页的路径 --><context-param><param-name>HOME_PAGE_PATH</param-name><param-value>/home/whf/workspace-sts/codeschool/home.html</param-value></context-param>

这样在我们在訪问主页的时候就能明显感觉到速度大大加快。