java高并发-静态页面生成方案(2)

本章将实现一个servlet生成html的基本功能，包含了URL 重定向功能
 

     现在我们来看看一个普通的url分页请求怎么生成静态页面。

   
      假如现在要显示第一页的数据信息 ，那么通常的链接会是这个样子 : http://abc.com/ xx.do?pageNumber=1  。我们说一下这个最简单的方式,打个比方：当我们访问 http://abc.com/ xx_pageNumber_1.shtml   的时候 ，就是在访问 http://abc.com/ xx.do?pageNumber=1  。规律就是请求的 action(动作)，和参数的名称，参数的值， 都用下滑线分开 ，而且请求的网页的最终后缀是 .shtm 。然后呢？我们需要编写一个servlet，去处理 .shtm 的请求： 

    

< servlet >
< servlet-name >creatorHtmlServlet servlet-name >
   < servlet-class >com.jlins.CreatorHtmlServlet servlet-class >
   < load-on-startup >2 load-on-startup >
servlet >
< servlet-mapping >
  < servlet-name >creatorHtmlServlet servlet-name >
  < url-pattern >*.shtm url-pattern >
servlet-mapping >

     下面就是 servlet 的内容了： 

public class CreatorHtmlServlet extends HttpServlet {

     private Logger log=Logger.getLogger(CreatorHtmlServlet. class );

     public void doGet(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException {
          doPost(request, response);
     }

     public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

          String encoding = "UTF-8" ;
          //获得请求address
          String templatePath = URLReWrite(request);
      //获得相对路径
          String realPath= request.getSession().getServletContext().getRealPath( "/" );
          //获得要生成的静态html文件的名字
          String htmlName = getHtmlFileName(request);
          //获得详细路径的 html文件的名字
          String cachhtmlFileName = realPath + File.separator + htmlName;

          File cacheFile = new File(cachhtmlFileName);

          boolean load = true ;
          //文件存在的话就可以直接返回了，不需要做任何处理
          if (cacheFile.exists()) {
             load = false ;
          }
          if (load) {
             final ByteArrayOutputStream os = new ByteArrayOutputStream();
             final ServletOutputStream stream = new ServletOutputStream() {

                  public   void   write( byte [] data, int offset, int length)   {
                         os.write(data,   offset,   length);
                  }

                  public   void   write( int   b)   throws   IOException   {
                         os.write(b);
                  }
              };

               final PrintWriter pw = new PrintWriter( new OutputStreamWriter(os, encoding));

               HttpServletResponse rep =  new HttpServletResponseWrapper(response)   {

                   public ServletOutputStream getOutputStream() {
                                  return stream;
                   }

                   public PrintWriter getWriter() {
                                 return pw;
           }
               };

              logger.debug( "HtmlCreatorServlet RequestDispatcher = " + templatePath);
              //  使用 RequestDispatcher转发请求，请求真是的地址
              //  例如 index.shtm ，则转发到 index.do
              RequestDispatcher  dispatcher = getServletContext().getRequestDispatcher(templatePath);
              dispatcher.include(request, rep);
              pw.flush();
              FileOutputStream fos = null ;
              try {

                  if (os.size() == 0 ) {
                  // 验证一下用户转发的地址是否有效，无效的话就提示错误
                  response.sendError(HttpServletResponse.SC_NOT_FOUND, "" );
                  }
          else {
                  // servlet调用其他命令在相应的目录生成html文件，并且把文件返回给客户端
                  fos = new FileOutputStream(cachhtmlFileName);
                  os.writeTo(fos);
                  dispatcher = getServletContext(). getRequestDispatcher( "/" +htmlName);
                        dispatcher.include(request, response);
                  }

                  } finally {
                  if (fos != null ) {
                      fos.close();
                  }
             }

             } else {
                  RequestDispatcher dispatcher = getServletContext().getRequestDispatcher( "/" +htmlName);                           dispatcher.include(request, response);
               }
            }
           // 主要的功能就是把http://abc.com/xx_pageNumber_1.shtm
           // 转换成 http://abc.com/xx.do?pageNumber=1  形式
           protected String URLReWrite(HttpServletRequest request) throws ServletException, IOException {
               String uri = request.getRequestURI();
               String contextPath = request.getContextPath();
               logger.debug( "HtmlCreator contextPath = " + contextPath);
               if (contextPath != null && contextPath.length() > 0 )
                   uri = uri.substring(contextPath.length());

                   uri = uri.substring( 0 , uri.length()- 5 );

                   String[] urls = uri.split( "_" );

                   uri = urls[ 0 ] + ".do" ;
                   if (urls.length > 1 ) {
                      for ( int i = 1 ; i < urls.length; i += 2 ) {
                      if (i== 1 ) {
                          uri += "?" + urls[i] + "=" + urls[i+ 1 ];
                      } else {
                        uri += "&" + urls[i] + "=" + urls[i+ 1 ];
                      }
                  }
                }

             logger.debug( "HtmlCreatorServlet get uri = " + uri);

             return uri;
          }
           // 主要功能根据 http://abc.com/xx_pageNumber_1.shtm
           // 来得到即将要生成的html文件名字，也就是 xx_pageNumber_1.html
          private String getHtmlFileName(HttpServletRequest request) throws ServletException, IOException{   String uri = request.getRequestURI();
              String contextPath = request.getContextPath();
              if (contextPath != null && contextPath.length() > 0 )
              uri = uri.substring(contextPath.length());

              uri = uri.substring( 1 , uri.length()- 5 );
              uri += ".html" ;
              return uri;
          }

 上面就是整个代码了，非常的简单吧

本人原创文章@www.javady.com 转载请标明出处 http://www.javady.com/index.php/95.html