[百分共享，up者有之]petstore中templateServlet原码解读，请诸位老大帮忙看看

Question

public void process (HttpServletRequest request,
                         HttpServletResponse  response)
       throws IOException, ServletException {       String screenName = null;
       String localeString = null;
       String selectedUrl = request.getRequestURI();
       if (request.getSession().getAttribute(WebKeys.CURRENT_URL) != null) {
           request.getSession().removeAttribute(WebKeys.CURRENT_URL);
       }
/*这个if语句快有什么作用？从哪儿取值，为什么取出来以后又要remove掉呢？*/       String languageParam = request.getParameter("locale");
/*这个local从哪儿取呢？*/
       // The language when specified as a parameter overrides the language set in the session
       if (languageParam != null) {
           localeString = languageParam;
       } else if (request.getSession().getAttribute(WebKeys.LOCALE) != null) {
           localeString = ((Locale)request.getSession().getAttribute(WebKeys.LOCALE)).toString();
/*这个又是从哪儿取的呢？*/
       }
       if (allScreens.get(localeString) == null) {
          localeString = defaultLocale;
/*这儿的localString值是多少*/
       }       // get the screen name
       int lastPathSeparator = selectedUrl.lastIndexOf("/") + 1;
       int lastDot = selectedUrl.lastIndexOf(".");
       if (lastPathSeparator != -1 && lastDot != -1 && lastDot > lastPathSeparator) {
           screenName = selectedUrl.substring(lastPathSeparator, lastDot);
/*这儿的screenName是多少？*/
       }
        // check if request is for the previous screen
/*这个if语句块有什么作用？以下的看不懂了，请大家帮忙*/
       if (screenName.equals(PREVIOUS_SCREEN)) {
           String longScreenName  =  (String)request.getSession().getAttribute(WebKeys.PREVIOUS_SCREEN);
           int lastDot2 = longScreenName.lastIndexOf(".");
           if ( lastDot2 != -1 && lastDot2 > 0) {
               screenName = longScreenName.substring(0, lastDot2);
            }
           // put the request attributes stored in the session in the request
           if (cachePreviousScreenParameters) {
               Map previousParams = (Map)request.getSession().getAttribute(WebKeys.PREVIOUS_REQUEST_PARAMETERS);
               Map params = (Map)request.getParameterMap();
               Iterator it = previousParams.keySet().iterator();
               while (it.hasNext()) {
                   String key = (String)it.next();
                   Object value = previousParams.get(key);
                   params.put(key,value);
               }
           }
           // put in the previous request attributes
           if (cachePreviousScreenAttributes) {
               Map previousAttributes = (Map)request.getSession().getAttribute(WebKeys.PREVIOUS_REQUEST_ATTRIBUTES);
               Iterator it2 = previousAttributes.keySet().iterator();
               // put the request attributes stored in the session in the request
               while (it2.hasNext()) {
                   String key = (String)it2.next();
                   Object value = previousAttributes.get(key);
                   request.setAttribute(key,value);
               }
           }
       } else {
                 String extension = selectedUrl.substring(lastDot, selectedUrl.length());
                 request.getSession().setAttribute(WebKeys.PREVIOUS_SCREEN, screenName + extension);
                 if (cachePreviousScreenParameters) {
                     // copy all the parameters into a new map
                     HashMap newParams =  new HashMap();
                     Map params = (Map)request.getParameterMap();
                     Iterator it = params.keySet().iterator();
                    // put the request attributes stored in the session in the request
                    while (it.hasNext()) {
                        String key = (String)it.next();
                        Object value = params.get(key);
                        newParams.put(key,value);
                    }
                    request.getSession().setAttribute(WebKeys.PREVIOUS_REQUEST_PARAMETERS, newParams);
                 }
                 if (cachePreviousScreenAttributes) {
                    // put the request attributes into a map
                    HashMap attributes = new HashMap();
                    Enumeration enum = request.getAttributeNames();
                    while (enum.hasMoreElements()) {
                        String key = (String)enum.nextElement();
                        Object value = request.getAttribute(key);
                        attributes.put(key, value);
                    }
                    request.getSession().setAttribute(WebKeys.PREVIOUS_REQUEST_ATTRIBUTES, attributes);
                 }
       }
       // get the screen information for the coresponding language
       Screen screen = null;
       if (screenName != null){
           Screens localeScreens = (Screens)allScreens.get(localeString);
           if (localeScreens != null) screen = (Screen)localeScreens.getScreen(screenName);
           // default to the default locale screen if it was not defined in the locale specific definitions
           if (screen == null) {
               System.err.println("Screen not Found loading default from " + defaultLocale);
               localeScreens = (Screens)allScreens.get(defaultLocale);
               screen = (Screen)localeScreens.getScreen(screenName);
           }
           if (screen != null) {
               request.setAttribute(WebKeys.CURRENT_SCREEN, screen);
               String templateName = localeScreens.getTemplate(screenName);
               if (templateName != null) {
                   insertTemplate(request, response, templateName);
               }
           } else {
               response.setContentType("text/html;charset=8859_1");
               PrintWriter out = response.getWriter();
               out.println("<font size=+4>Error:</font><br>Definition for screen " + screenName + " not found");
           }
       }
   }   private void insertTemplate(HttpServletRequest request,
                               HttpServletResponse response,
                               String templateName)
       throws IOException, ServletException {   }

Answer 1

你应该看看对应的web.xml，里面有对应的参数：
        <servlet>
<servlet-name>TemplateServlet</servlet-name>
<display-name>TemplateServlet</display-name>
<servlet-class>com.sun.j2ee.blueprints.waf.view.template.TemplateServlet</servlet-class>
<init-param>
<param-name>cache_previous_screen_attributes</param-name>
<param-value>false</param-value>
</init-param>
<init-param>
<param-name>cache_previous_screen_parameters</param-name>
<param-value>false</param-value>
</init-param>
<init-param>
<param-name>default_locale</param-name>
<param-value>en_US</param-value>
</init-param>
<init-param>
<param-name>locales</param-name>
<param-value>en_US</param-value>
</init-param>
<load-on-startup>2</load-on-startup>
</servlet>
以及mappings.xml和对应的screendefinitions_en_US.xml
总体都看看就知道了。

Answer 2

我看了web.xml、mapping.xml、screendefinition_en_Us.xml，但还是不明白
比如：String cachePreviousScreenAttributesString = config.getInitParameter("cache_previous_screen_attributes");
这个值从哪儿来的呢

Answer 3

我给你发了封邮件，里面是对petstore的解释