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(); } }
时间: 2024-10-19 21:12:27