WebUtils工具类解析
WebUtils根据名称，知道是Spring当中一个工具类，主要用于Web应用程序，供各种框架使用。
其中有些方法还是挺有用的，比如可以获取Session中的会话属性，获取Cookies，设置Session中的会话属性的值等等
翻译了WebUtils类的文档，其中WebUtils中的方法如下：
1.将一个系统性质设置到上下文根路径
-
public static void setWebAppRootSystemProperty(ServletContext servletContext) throws IllegalStateException {
-
Assert.notNull(servletContext,
"ServletContext must not be null");
-
String root = servletContext.getRealPath(
"/");
-
if (root ==
null) {
-
throw
new IllegalStateException(
-
"Cannot set web app root system property when WAR file is not expanded");
-
}
-
String param = servletContext.getInitParameter(WEB_APP_ROOT_KEY_PARAM);
-
String key = (param !=
null ? param : DEFAULT_WEB_APP_ROOT_KEY);
-
String oldValue = System.getProperty(key);
-
if (oldValue !=
null && !StringUtils.pathEquals(oldValue, root)) {
-
throw
new IllegalStateException(
-
"Web app root system property already set to different value: '" +
-
key +
"' = [" + oldValue +
"] instead of [" + root +
"] - " +
-
"Choose unique values for the 'webAppRootKey' context-param in your web.xml files!");
-
}
-
System.setProperty(key, root);
-
servletContext.log(
"Set web app root system property: '" + key +
"' = [" + root +
"]");
-
}
2.移除系统性质
-
public static void removeWebAppRootSystemProperty(ServletContext servletContext) {
-
Assert.notNull(servletContext,
"ServletContext must not be null");
-
String param = servletContext.getInitParameter(WEB_APP_ROOT_KEY_PARAM);
-
String key = (param !=
null ? param : DEFAULT_WEB_APP_ROOT_KEY);
-
System.getProperties().remove(key);
-
}
3.判断“HTML escaping”(HTML转义)对应用是否允许，即看web.xml中的defaultHtmlEscape的值是否设置为true
-
public static Boolean getDefaultHtmlEscape(ServletContext servletContext) {
-
if (servletContext ==
null) {
-
return
null;
-
}
-
String param = servletContext.getInitParameter(HTML_ESCAPE_CONTEXT_PARAM);
-
return (StringUtils.hasText(param)? Boolean.valueOf(param) :
null);
-
}
4.返回由当前servlet容器提供的 当前Web应用程序的临时目录
-
public static File getTempDir(ServletContext servletContext) {
-
Assert.notNull(servletContext,
"ServletContext must not be null");
-
return (File) servletContext.getAttribute(TEMP_DIR_CONTEXT_ATTRIBUTE);
-
}
5.返回由servlet容器提供的，Web应用程序中给定路径的实际路径
-
public static String getRealPath(ServletContext servletContext, String path) throws FileNotFoundException {
-
Assert.notNull(servletContext,
"ServletContext must not be null");
-
// Interpret location as relative to the web application root directory.
-
if (!path.startsWith(
"/")) {
-
path =
"/" + path;
-
}
-
String realPath = servletContext.getRealPath(path);
-
if (realPath ==
null) {
-
throw
new FileNotFoundException(
-
"ServletContext resource [" + path +
"] cannot be resolved to absolute file path - " +
-
"web application archive not expanded?");
-
}
-
return realPath;
-
}
6.通过一个请求确定会话Session的标识(Id)
-
public static String getSessionId(HttpServletRequest request) {
-
Assert.notNull(request,
"Request must not be null");
-
HttpSession session = request.getSession(
false);
-
return (session !=
null ? session.getId() :
null);
-
}
7.通过一个请求，通过name获取session中的属性，如果session中没有属性或者没有session会返回一个null
-
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);
-
}
8.和7中方法相似，只不过不会返回null，会抛出异常
-
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;
-
}
9.通过给定的名称和值设置session中的属性，若果session值为空，会移除session的属性
-
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);
-
}
-
}
-
}
10.获取指定的会话属性，如果没有找到的话会创建并设置新的属性。其中给定的类需要有一个公共的无参构造函数。
-
public static Object getOrCreateSessionAttribute(HttpSession session, String name, Class clazz)
-
throws IllegalArgumentException {
-
-
Assert.notNull(session,
"Session must not be null");
-
Object sessionObject = session.getAttribute(name);
-
if (sessionObject ==
null) {
-
try {
-
sessionObject = clazz.newInstance();
-
}
-
catch (InstantiationException ex) {
-
throw
new IllegalArgumentException(
-
"Could not instantiate class [" + clazz.getName() +
-
"] for session attribute '" + name +
"': " + ex.getMessage());
-
}
-
catch (IllegalAccessException ex) {
-
throw
new IllegalArgumentException(
-
"Could not access default constructor of class [" + clazz.getName() +
-
"] for session attribute '" + name +
"': " + ex.getMessage());
-
}
-
session.setAttribute(name, sessionObject);
-
}
-
return sessionObject;
-
}
11.返回给定会话的最佳可用互斥量：即为给定会话同步的对象。返回会话互斥属性（如果可用）;通常情况下，这意味着需要定义HttpSessionMutexListener在{code web.xml}中。 回到HttpSession本身如果没有找到互斥属性。会话互斥确保在期间是相同的对象会话的整个生命周期，在定义的密钥下可用由SESSION_MUTEX_ATTRIBUTE常量定义。 它作为一个在当前会话上同步锁定的安全引用。在很多情况下，HttpSession引用本身是一个安全的互斥体同样，因为它始终是相同的对象参考相同的活动逻辑会话。 但是，这并不能保证不同的servlet容器; 唯一的100％安全方式是会话互斥。
-
public static Object getSessionMutex(HttpSession session) {
-
Assert.notNull(session,
"Session must not be null");
-
Object mutex = session.getAttribute(SESSION_MUTEX_ATTRIBUTE);
-
if (mutex ==
null) {
-
mutex = session;
-
}
-
return mutex;
-
}
12.返回指定类型的合适的请求对象，如果可用，会unwrapping给定的request请求
-
public
static
T getNativeRequest(ServletRequest request, Class requiredType) {
-
if (requiredType !=
null) {
-
if (requiredType.isInstance(request)) {
-
return (T) request;
-
}
-
else
if (request
instanceof ServletRequestWrapper) {
-
return getNativeRequest(((ServletRequestWrapper) request).getRequest(), requiredType);
-
}
-
}
-
return
null;
-
}
13.和12方法类似，应用于response
-
public
static
T getNativeResponse(ServletResponse response, Class requiredType) {
-
if (requiredType !=
null) {
-
if (requiredType.isInstance(response)) {
-
return (T) response;
-
}
-
else
if (response
instanceof ServletResponseWrapper) {
-
return getNativeResponse(((ServletResponseWrapper) response).getResponse(), requiredType);
-
}
-
}
-
return
null;
-
}
14.判断请求是否是一个包含(Include)请求，即不是从外部进入的顶级Http请求。
-
public static boolean isIncludeRequest(ServletRequest request) {
-
return (request.getAttribute(INCLUDE_REQUEST_URI_ATTRIBUTE) !=
null);
-
}
15.Servlet规范的错误属性，Servlet2.3规范中定义的属性，用于错误页面直接呈现，而不是通过Servlet容器的错误页面解析
-
public static void exposeErrorRequestAttributes(HttpServletRequest request, Throwable ex, String servletName) {
-
exposeRequestAttributeIfNotPresent(request, ERROR_STATUS_CODE_ATTRIBUTE, HttpServletResponse.SC_OK);
-
exposeRequestAttributeIfNotPresent(request, ERROR_EXCEPTION_TYPE_ATTRIBUTE, ex.getClass());
-
exposeRequestAttributeIfNotPresent(request, ERROR_MESSAGE_ATTRIBUTE, ex.getMessage());
-
exposeRequestAttributeIfNotPresent(request, ERROR_EXCEPTION_ATTRIBUTE, ex);
-
exposeRequestAttributeIfNotPresent(request, ERROR_REQUEST_URI_ATTRIBUTE, request.getRequestURI());
-
exposeRequestAttributeIfNotPresent(request, ERROR_SERVLET_NAME_ATTRIBUTE, servletName);
-
}
16.如果不存在？ 公开指定的请求属性 （有疑问）
-
private static void exposeRequestAttributeIfNotPresent(ServletRequest request, String name, Object value) {
-
if (request.getAttribute(name) ==
null) {
-
request.setAttribute(name, value);
-
}
-
}
17.清除类似方法15中定义的错误属性，遵循servlet2.3规范
-
public static void clearErrorRequestAttributes(HttpServletRequest request) {
-
request.removeAttribute(ERROR_STATUS_CODE_ATTRIBUTE);
-
request.removeAttribute(ERROR_EXCEPTION_TYPE_ATTRIBUTE);
-
request.removeAttribute(ERROR_MESSAGE_ATTRIBUTE);
-
request.removeAttribute(ERROR_EXCEPTION_ATTRIBUTE);
-
request.removeAttribute(ERROR_REQUEST_URI_ATTRIBUTE);
-
request.removeAttribute(ERROR_SERVLET_NAME_ATTRIBUTE);
-
}
18.将给定的Map公开为请求属性，使用键作为属性名称并将值作为相应的属性值。 键需要是字符串
-
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());
-
}
-
}
19.检索具有给定名称的第一个cookie。注意多个Cookie可以具有相同的名称，但路径和域不同。
-
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;
-
}
20.检查请求中是否有通过按钮或者图像的特定的输入类型=“submit”参数
-
public static boolean hasSubmitParameter(ServletRequest request, String name) {
-
Assert.notNull(request,
"Request must not be null");
-
if (request.getParameter(name) !=
null) {
-
return
true;
-
}
-
for (String suffix : SUBMIT_IMAGE_SUFFIXES) {
-
if (request.getParameter(name + suffix) !=
null) {
-
return
true;
-
}
-
}
-
return
false;
-
}
21.从给定的请求参数中获取一个命名参数。可以参阅方法{findParameterValue}用于查找算法的描述
-
public static String findParameterValue(ServletRequest request, String name) {
-
return findParameterValue(request.getParameterMap(), name);
-
}
22.获取参数值通过以下的算法：（算法补充）
-
public static String findParameterValue(Map
parameters, String name) {
-
// First try to get it as a normal name=value parameter
-
Object value = parameters.get(name);
-
if (value
instanceof String[]) {
-
String[] values = (String[]) value;
-
return (values.length >
0 ? values[
0] :
null);
-
}
-
else
if (value !=
null) {
-
return value.toString();
-
}
-
// If no value yet, try to get it as a name_value=xyz parameter
-
String prefix = name +
"_";
-
for (String paramName : parameters.keySet()) {
-
if (paramName.startsWith(prefix)) {
-
// Support images buttons, which would submit parameters as name_value.x=123
-
for (String suffix : SUBMIT_IMAGE_SUFFIXES) {
-
if (paramName.endsWith(suffix)) {
-
return paramName.substring(prefix.length(), paramName.length() - suffix.length());
-
}
-
}
-
return paramName.substring(prefix.length());
-
}
-
}
-
// We couldn't find the parameter value...
-
return
null;
-
}
23.返回包含具有给定前缀的所有参数的map。将单个值映射为String，多个值映射到String数组。
-
public static Map
getParametersStartingWith(ServletRequest request, String prefix) {
-
Assert.notNull(request,
"Request must not be null");
-
Enumeration
paramNames = request.getParameterNames();
-
Map
params =
new TreeMap();
-
if (prefix ==
null) {
-
prefix =
"";
-
}
-
while (paramNames !=
null && paramNames.hasMoreElements()) {
-
String paramName = paramNames.nextElement();
-
if (
"".equals(prefix) || paramName.startsWith(prefix)) {
-
String unprefixed = paramName.substring(prefix.length());
-
String[] values = request.getParameterValues(paramName);
-
if (values ==
null || values.length ==
0) {
-
// Do nothing, no values found at all.
-
}
-
else
if (values.length >
1) {
-
params.put(unprefixed, values);
-
}
-
else {
-
params.put(unprefixed, values[
0]);
-
}
-
}
-
}
-
return params;
-
}
24.返回请求中指定的目标页面
-
public static int getTargetPage(ServletRequest request, String paramPrefix, int currentPage) {
-
Enumeration
paramNames = request.getParameterNames();
-
while (paramNames.hasMoreElements()) {
-
String paramName = paramNames.nextElement();
-
if (paramName.startsWith(paramPrefix)) {
-
for (
int i =
0; i < WebUtils.SUBMIT_IMAGE_SUFFIXES.length; i++) {
-
String suffix = WebUtils.SUBMIT_IMAGE_SUFFIXES[i];
-
if (paramName.endsWith(suffix)) {
-
paramName = paramName.substring(
0, paramName.length() - suffix.length());
-
}
-
}
-
return Integer.parseInt(paramName.substring(paramPrefix.length()));
-
}
-
}
-
return currentPage;
-
}
25.从给定的请求URL路径中提取URL文件名
-
public static String extractFilenameFromUrlPath(String urlPath) {
-
String filename = extractFullFilenameFromUrlPath(urlPath);
-
int dotIndex = filename.lastIndexOf(
'.');
-
if (dotIndex != -
1) {
-
filename = filename.substring(
0, dotIndex);
-
}
-
return filename;
-
}
26.从给定的请求URL路径中提取完整的URL文件名（包括文件扩展名）。正确地解析嵌套路径，例如“/products/view.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);
-
}
使用值{@code [“a”，“b”]}的密钥{@code“q1”}和{@code“q2”}和{@code [“a”，“b”，“c”]}。
-
public static MultiValueMap
parseMatrixVariables(String matrixVariables) {
-
MultiValueMap
result =
new LinkedMultiValueMap();
-
if (!StringUtils.hasText(matrixVariables)) {
-
return result;
-
}
-
StringTokenizer pairs =
new StringTokenizer(matrixVariables,
";");
-
while (pairs.hasMoreTokens()) {
-
String pair = pairs.nextToken();
-
int index = pair.indexOf(
'=');
-
if (index != -
1) {
-
String name = pair.substring(
0, index);
-
String rawValue = pair.substring(index +
1);
-
for (String value : StringUtils.commaDelimitedListToStringArray(rawValue)) {
-
result.add(name, value);
-
}
-
}
-
else {
-
result.add(pair,
"");
-
}
-
}
-
return result;
-
}