org.springframework.web.util
Class WebUtils

java.lang.Object
  org.springframework.web.util.WebUtils

public abstract class WebUtils
extends Object

Miscellaneous utilities for web applications. Used by various framework classes.

Author:

Rod Johnson, Juergen Hoeller

Field Summary

static String	CONTENT_TYPE_CHARSET_PREFIX Prefix of the charset clause in a content type String: ";charset="
static String	DEFAULT_CHARACTER_ENCODING Default character encoding to use when request.getCharacterEncoding returns null, according to the Servlet spec.
static String	DEFAULT_WEB_APP_ROOT_KEY Default web app root key: "webapp.root"
static String	HTML_ESCAPE_CONTEXT_PARAM HTML escape parameter at the servlet context level (i.e. a context-param in web.xml): "defaultHtmlEscape".
static String	SESSION_MUTEX_ATTRIBUTE
static String[]	SUBMIT_IMAGE_SUFFIXES Name suffixes in case of image buttons
static String	TEMP_DIR_CONTEXT_ATTRIBUTE Standard Servlet spec context attribute that specifies a temporary directory for the current web application, of type java.io.File.
static String	WEB_APP_ROOT_KEY_PARAM Web app root key parameter at the servlet context level (i.e. a context-param in web.xml): "webAppRootKey".

Constructor Summary

WebUtils()

Method Summary

static void	exposeRequestAttributes(ServletRequest request, Map attributes) Expose the given Map as request attributes, using the keys as attribute names and the values as corresponding attribute values.
static String	extractFilenameFromUrlPath(String urlPath) Extract the URL filename from the given request URL path.
static Cookie	getCookie(HttpServletRequest request, String name) Retrieve the first cookie with the given name.
static Object	getOrCreateSessionAttribute(HttpSession session, String name, Class clazz) Get the specified session attribute, creating and setting a new attribute if no existing found.
static Map	getParametersStartingWith(ServletRequest request, String prefix) Return a map containing all parameters with the given prefix.
static String	getRealPath(ServletContext servletContext, String path) Return the real path of the given path within the web application, as provided by the servlet container.
static Object	getRequiredSessionAttribute(HttpServletRequest request, String name) Check the given request for a session attribute of the given name.
static Object	getSessionAttribute(HttpServletRequest request, String name) Check the given request for a session attribute of the given name.
static String	getSessionId(HttpServletRequest request) Determine the session id of the given request, if any.
static Object	getSessionMutex(HttpSession session) Return the best available mutex for the given session: that is, an object to synchronize on for the given session.
static File	getTempDir(ServletContext servletContext) Return the temporary directory for the current web application, as provided by the servlet container.
static boolean	hasSubmitParameter(ServletRequest request, String name) Check if a specific input type="submit" parameter was sent in the request, either via a button (directly with name) or via an image (name + ".x" or name + ".y").
static boolean	isDefaultHtmlEscape(ServletContext servletContext) Return whether default HTML escaping is enabled for the web application, i.e. the value of the "defaultHtmlEscape" context-param in web.xml (if any).
static boolean	isIncludeRequest(ServletRequest request) Determine whether the given request is an include request, that is, not a top-level HTTP request coming in from the outside.
static void	removeWebAppRootSystemProperty(ServletContext servletContext) Remove the system property that points to the web app root directory.
static void	setSessionAttribute(HttpServletRequest request, String name, Object value) Set the session attribute with the given name to the given value.
static void	setWebAppRootSystemProperty(ServletContext servletContext) Set a system property to the web application root directory.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CONTENT_TYPE_CHARSET_PREFIX

public static final String CONTENT_TYPE_CHARSET_PREFIX

Prefix of the charset clause in a content type String: ";charset="

See Also:

Constant Field Values

DEFAULT_CHARACTER_ENCODING

public static final String DEFAULT_CHARACTER_ENCODING

Default character encoding to use when request.getCharacterEncoding returns null, according to the Servlet spec.

See Also:

ServletRequest.getCharacterEncoding(), Constant Field Values

TEMP_DIR_CONTEXT_ATTRIBUTE

public static final String TEMP_DIR_CONTEXT_ATTRIBUTE

Standard Servlet spec context attribute that specifies a temporary directory for the current web application, of type java.io.File.

See Also:

Constant Field Values

HTML_ESCAPE_CONTEXT_PARAM

public static final String HTML_ESCAPE_CONTEXT_PARAM

HTML escape parameter at the servlet context level (i.e. a context-param in web.xml): "defaultHtmlEscape".

See Also:

Constant Field Values

WEB_APP_ROOT_KEY_PARAM

public static final String WEB_APP_ROOT_KEY_PARAM

Web app root key parameter at the servlet context level (i.e. a context-param in web.xml): "webAppRootKey".

See Also:

Constant Field Values

DEFAULT_WEB_APP_ROOT_KEY

public static final String DEFAULT_WEB_APP_ROOT_KEY

Default web app root key: "webapp.root"

See Also:

Constant Field Values

SUBMIT_IMAGE_SUFFIXES

public static final String[] SUBMIT_IMAGE_SUFFIXES

Name suffixes in case of image buttons

SESSION_MUTEX_ATTRIBUTE

public static final String SESSION_MUTEX_ATTRIBUTE

Constructor Detail

WebUtils

public WebUtils()

Method Detail

setWebAppRootSystemProperty

public static void setWebAppRootSystemProperty(ServletContext servletContext)
                                        throws IllegalStateException

Set a system property to the web application root directory. The key of the system property can be defined with the "webAppRootKey" context-param in web.xml. Default is "webapp.root".

Can be used for tools that support substition with System.getProperty values, like Log4J's "${key}" syntax within log file locations.

Parameters:

servletContext - the servlet context of the web application

Throws:

IllegalStateException - if the system property is already set, or if the WAR file is not expanded

See Also:

WEB_APP_ROOT_KEY_PARAM, DEFAULT_WEB_APP_ROOT_KEY, WebAppRootListener, Log4jWebConfigurer

removeWebAppRootSystemProperty

public static void removeWebAppRootSystemProperty(ServletContext servletContext)

Remove the system property that points to the web app root directory. To be called on shutdown of the web application.

Parameters:

servletContext - the servlet context of the web application

See Also:

setWebAppRootSystemProperty(javax.servlet.ServletContext)

isDefaultHtmlEscape

public static boolean isDefaultHtmlEscape(ServletContext servletContext)

Return whether default HTML escaping is enabled for the web application, i.e. the value of the "defaultHtmlEscape" context-param in web.xml (if any).

Parameters:

servletContext - the servlet context of the web application

Returns:

whether default HTML escaping is enabled (default is false)

getTempDir

public static File getTempDir(ServletContext servletContext)

Return the temporary directory for the current web application, as provided by the servlet container.

Parameters:

servletContext - the servlet context of the web application

Returns:

the File representing the temporary directory

getRealPath

public static String getRealPath(ServletContext servletContext,
                                 String path)
                          throws FileNotFoundException

Return the real path of the given path within the web application, as provided by the servlet container.

Prepends a slash if the path does not already start with a slash, and throws a FileNotFoundException if the path cannot be resolved to a resource (in contrast to ServletContext's getRealPath, which returns null).

Parameters:

servletContext - the servlet context of the web application

Returns:

the corresponding real path

Throws:

FileNotFoundException - if the path cannot be resolved to a resource

See Also:

ServletContext.getRealPath(java.lang.String)

getSessionId

public static String getSessionId(HttpServletRequest request)

Determine the session id of the given request, if any.

Parameters:

request - current HTTP request

Returns:

the session id, or null if none

getSessionAttribute

public static Object getSessionAttribute(HttpServletRequest request,
                                         String name)

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!

Parameters:

request - current HTTP request

name - the name of the session attribute

Returns:

the value of the session attribute, or null if not found

getRequiredSessionAttribute

public static Object getRequiredSessionAttribute(HttpServletRequest request,
                                                 String name)
                                          throws IllegalStateException

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!

Parameters:

request - current HTTP request

name - the name of the session attribute

Returns:

the value of the session attribute, or null if not found

Throws:

IllegalStateException - if the session attribute could not be found

setSessionAttribute

public static void setSessionAttribute(HttpServletRequest request,
                                       String name,
                                       Object value)

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!

Parameters:

request - current HTTP request

name - the name of the session attribute

getOrCreateSessionAttribute

public static Object getOrCreateSessionAttribute(HttpSession session,
                                                 String name,
                                                 Class clazz)
                                          throws IllegalArgumentException

Get the specified session attribute, creating and setting a new attribute if no existing found. The given class needs to have a public no-arg constructor. Useful for on-demand state objects in a web tier, like shopping carts.

Parameters:

session - current HTTP session

name - the name of the session attribute

clazz - the class to instantiate for a new attribute

Returns:

the value of the session attribute, newly created if not found

Throws:

IllegalArgumentException - if the session attribute could not be instantiated

getSessionMutex

public static Object getSessionMutex(HttpSession session)

Return the best available mutex for the given session: that is, an object to synchronize on for the given session.

Returns the session mutex attribute if available; usually, this means that the HttpSessionMutexListener needs to be defined in web.xml. Falls back to the HttpSession itself if no mutex attribute found.

The session mutex is guaranteed to be the same object during the entire lifetime of the session, available under the key defined by the SESSION_MUTEX_ATTRIBUTE constant. It serves as a safe reference to synchronize on for locking on the current session.

In many cases, the HttpSession reference itself is a safe mutex as well, since it will always be the same object reference for the same active logical session. However, this is not guaranteed across different servlet containers; the only 100% safe way is a session mutex.

Parameters:

session - the HttpSession to find a mutex for

Returns:

the mutex object (never null)

See Also:

SESSION_MUTEX_ATTRIBUTE, HttpSessionMutexListener

exposeRequestAttributes

public static void exposeRequestAttributes(ServletRequest request,
                                           Map attributes)
                                    throws IllegalArgumentException

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.

Parameters:

request - current HTTP request

attributes - the attributes Map

Throws:

IllegalArgumentException - if an invalid key is found in the Map

getCookie

public static Cookie getCookie(HttpServletRequest request,
                               String name)

Retrieve the first cookie with the given name. Note that multiple cookies can have the same name but different paths or domains.

Parameters:

name - cookie name

Returns:

the first cookie with the given name, or null if none is found

isIncludeRequest

public static boolean isIncludeRequest(ServletRequest request)

Determine whether the given request is an include request, that is, not a top-level HTTP request coming in from the outside.

Checks the presence of the "javax.servlet.include.request_uri" request attribute. Could check any request attribute that is only present in an include request.

Parameters:

request - current servlet request

hasSubmitParameter

public static boolean hasSubmitParameter(ServletRequest request,
                                         String name)

Check if a specific input type="submit" parameter was sent in the request, either via a button (directly with name) or via an image (name + ".x" or name + ".y").

Parameters:

request - current HTTP request

name - name of the parameter

Returns:

if the parameter was sent

See Also:

SUBMIT_IMAGE_SUFFIXES

getParametersStartingWith

public static Map getParametersStartingWith(ServletRequest request,
                                            String prefix)

Return a map containing all parameters with the given prefix. Maps single values to String and multiple values to String array.

For example, with a prefix of "spring_", "spring_param1" and "spring_param2" result in a Map with "param1" and "param2" as keys.

Similar to Servlet 2.3's ServletRequest.getParameterMap, but more flexible and compatible with Servlet 2.2.

Parameters:

request - HTTP request in which to look for parameters

prefix - the beginning of parameter names (if this is null or the empty string, all parameters will match)

Returns:

map containing request parameters without the prefix, containing either a String or a String array as values

See Also:

ServletRequest.getParameterNames(), ServletRequest.getParameterValues(java.lang.String), ServletRequest.getParameterMap()

extractFilenameFromUrlPath

public static String extractFilenameFromUrlPath(String urlPath)

Extract the URL filename from the given request URL path. Correctly resolves nested paths such as "/products/view.html" as well.

Parameters:

urlPath - the request URL path (e.g. "/index.html")

Returns:

the extracted URI filename (e.g. "index")