Spring中的WebUtils类

WebUtils
位于 org.springframework.web.util 包中的 WebUtils 是一个非常好用的工具类，它对很多 Servlet API 提供了易用的代理方法，降低了访问 Servlet API 的复杂度，可以将其看成是常用 Servlet API 方法的门面类。
下面这些方法为访问 HttpServletRequest 和 HttpSession 中的对象和属性带来了方便：

 

（1）getSessionAttribute

获取 HttpSession 特定属性名的对象，否则您必须通过 request.getSession.getAttribute(name) 完成相同的操作；

 /**
  * Check the given request for a session attribute of the given name.
  * Returns null if there is no session or if the session has no such attribute.
  * Does not create a new session if none has existed before!
  * @param request current HTTP request
  * @param name the name of the session attribute
  * @return the value of the session attribute, or null if not found
  */
 public static Object getSessionAttribute(HttpServletRequest request, String name) {
     Assert.notNull(request, "Request must not be null");
     HttpSession session = request.getSession(false);
     return (session != null ? session.getAttribute(name) : null);
 }

 （2）getRequiredSessionAttribute

和上一个方法类似，只不过强制要求 HttpSession 中拥有指定的属性，否则抛出异常；

 /**
  * Check the given request for a session attribute of the given name.
  * Throws an exception if there is no session or if the session has no such
  * attribute. Does not create a new session if none has existed before!
  * @param request current HTTP request
  * @param name the name of the session attribute
  * @return the value of the session attribute, or null if not found
  * @throws IllegalStateException if the session attribute could not be found
  */
 public static Object getRequiredSessionAttribute(HttpServletRequest request, String name)
     throws IllegalStateException {

     Object attr = getSessionAttribute(request, name);
     if (attr == null) {
         throw new IllegalStateException("No session attribute '" + name + "' found");
     }
     return attr;
 }

 （3）setSessionAttribute

给session中的指定属性设置值，若传入值为空，则从session中移除该属性

 /**
  * Set the session attribute with the given name to the given value.
  * Removes the session attribute if value is null, if a session existed at all.
  * Does not create a new session if not necessary!
  * @param request current HTTP request
  * @param name the name of the session attribute
  * @param value the value of the session attribute
  */
 public static void setSessionAttribute(HttpServletRequest request, String name, Object value) {
     Assert.notNull(request, "Request must not be null");
     if (value != null) {
         request.getSession().setAttribute(name, value);
     }
     else {
         HttpSession session = request.getSession(false);
         if (session != null) {
             session.removeAttribute(name);
         }
     }
 }

 （4）exposeRequestAttributes

将 Map 元素添加到 ServletRequest 的属性列表中，当请求被导向（forward）到下一个处理程序时，这些请求属性就可以被访问到了；

 /**
  * Expose the given Map as request attributes, using the keys as attribute names
  * and the values as corresponding attribute values. Keys need to be Strings.
  * @param request current HTTP request
  * @param attributes the attributes Map
  */
 public static void exposeRequestAttributes(ServletRequest request, Map attributes) {
     Assert.notNull(request, "Request must not be null");
     Assert.notNull(attributes, "Attributes Map must not be null");
     for (Map.Entry entry : attributes.entrySet()) {
         request.setAttribute(entry.getKey(), entry.getValue());
     }
 }

 （5）getCookie

获取 HttpServletRequest 中特定名字的 Cookie 对象。如果您需要创建 Cookie， Spring 也提供了一个方便的 CookieGenerator 工具类；

 /**
  * Retrieve the first cookie with the given name. Note that multiple
  * cookies can have the same name but different paths or domains.
  * @param request current servlet request
  * @param name cookie name
  * @return the first cookie with the given name, or null if none is found
  */
 public static Cookie getCookie(HttpServletRequest request, String name) {
     Assert.notNull(request, "Request must not be null");
     Cookie cookies[] = request.getCookies();
     if (cookies != null) {
         for (Cookie cookie : cookies) {
             if (name.equals(cookie.getName())) {
                 return cookie;
             }
         }
     }
     return null;
 }

 （6）extractFilenameFromUrlPath

从Url地址中截取文件名称

 /**
  * Extract the URL filename from the given request URL path.
  * Correctly resolves nested paths such as "/products/view.html" as well.
  * @param urlPath the request URL path (e.g. "/index.html")
  * @return the extracted URI filename (e.g. "index")
  */
 public static String extractFilenameFromUrlPath(String urlPath) {
     String filename = extractFullFilenameFromUrlPath(urlPath);
     int dotIndex = filename.lastIndexOf('.');
     if (dotIndex != -1) {
         filename = filename.substring(0, dotIndex);
     }
     return filename;
 }

 /**
  * Extract the full URL filename (including file extension) from the given request URL path.
  * Correctly resolves nested paths such as "/products/view.html" as well.
  * @param urlPath the request URL path (e.g. "/products/index.html")
  * @return the extracted URI filename (e.g. "index.html")
  */
 public static String extractFullFilenameFromUrlPath(String urlPath) {
     int end = urlPath.indexOf(';');
     if (end == -1) {
         end = urlPath.indexOf('?');
         if (end == -1) {
             end = urlPath.length();
         }
     }
     int begin = urlPath.lastIndexOf('/', end) + 1;
     return urlPath.substring(begin, end);
 }