1 说明
静态页面本身就比动态页面快很多倍,而且动态页面总是要去数据库查询,这会更加降低速度!
页面静态化是把动态页面生成的html保存到服务器的文件上,然后再有相同请求时,不再去执行动态页面,而是直接给用户响应上次已经生成的静态页面。而且静态页面还有助与搜索引擎找到你!
2查看图书分类
我们先来写一个小例子,用来查看不同分类的图书。然后我们再去思考如何让动态页面静态化的问题。
index.jsp
<body><a href="<c:url value='/BookServlet'/>">全部图书</a><br/><a href="<c:url value='/BookServlet?category=1'/>">JavaSE分类</a><br/><a href="<c:url value='/BookServlet?category=2'/>">JavaEE分类</a><br/><a href="<c:url value='/BookServlet?category=3'/>">Java框架分类</a><br/> </body>
public class BookServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {BookService bookService = new BookService();List<Book> bookList = null;String param = request.getParameter("category");if(param == null || param.isEmpty()) {bookList = bookService.findAll();} else {int category = Integer.parseInt(param);bookList = bookService.findByCategory(category);}request.setAttribute("bookList", bookList);request.getRequestDispatcher("/show.jsp").forward(request, response);}}
show.jsp
<table border="1" align="center" width="50%"><tr><th>图书名称</th><th>图书单价</th><th>图书分类</th></tr> <c:forEach items="${bookList }" var="book"><tr><td>${book.bname }</td><td>${book.price }</td><td><c:choose><c:when test="${book.category eq 1}"><p style="color:red;">JavaSE分类</p></c:when><c:when test="${book.category eq 2}"><p style="color:blue;">JavaEE分类</p></c:when><c:when test="${book.category eq 3}"><p style="color:green;">Java框架分类</p></c:when></c:choose></td></tr> </c:forEach></table>
3分析
用户第一次访问页面时生成静态页面,然后让请求重定向到静态页面上去。当用户再次访问时,直接重定向到静态页面上去。
我们需要为不同的请求生成静态页面,例如用户访问BookServlet?category=1时,我们要生成静态页面,当用户访问BookServlet?category=2时,也要生成静态页面。即不同的参数生成不同的静态页面!
我们可以使用category为key,静态页面的路径为value,保存到一个Map中,然后再把Map保存到ServletContext中。没有对应的静态页面时,我们生成静态页面,再重定向到静态页面,如果存在静态页面,那么直接重定向即可。
public class StaticResponse extends HttpServletResponseWrapper {private PrintWriter pw;public StaticResponse(HttpServletResponse response, String filepath)throws FileNotFoundException, UnsupportedEncodingException {super(response);pw = new PrintWriter(filepath, "UTF-8");}public PrintWriter getWriter() throws IOException {return pw;}public void close() throws IOException {pw.close();}}
public class StaticFilter implements Filter {private ServletContext sc;public void destroy() {}public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {HttpServletRequest req = (HttpServletRequest) request;HttpServletResponse res = (HttpServletResponse) response;String key = "key_" + request.getParameter("category");Map<String,String> map = (Map<String, String>) sc.getAttribute("pages");if(map == null) {map = new HashMap<String,String>();sc.setAttribute("pages", map);}if(map.containsKey(key)) {res.sendRedirect(req.getContextPath() + "/staticPages/" + map.get(key));return;}String html = key + ".html";String realPath = sc.getRealPath("/staticPages/" + html);StaticResponse sr = new StaticResponse(res, realPath);chain.doFilter(request, sr);sr.close();res.sendRedirect(req.getContextPath() + "/staticPages/" + html);map.put(key, html);}public void init(FilterConfig fConfig) throws ServletException {this.sc = fConfig.getServletContext();}}
可你仍然感谢天地和人世所带来的这些变化和发生。