spring的WebUtils类源码解析

浏览数：37 / 时间：2015年06月08日

参考文章：1. http://www.ibm.com/developerworks/cn/java/j-lo-spring-utils1/

2.spring源码
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；

Java代码

/**
* 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 <code>null</code> 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；

Java代码

/**
* 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 <code>null</code> 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

Java代码

/**
* 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；

Java代码

/**
* 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<String, ?> attributes) {
Assert.notNull(request, "Request must not be null");
Assert.notNull(attributes, "Attributes Map must not be null");
for (Map.Entry<String, ?> 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；

Java代码

/**
* 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 <code>null</code> 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

Java代码

/**
* 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);
}