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	ERROR_EXCEPTION_ATTRIBUTE
static String	ERROR_EXCEPTION_TYPE_ATTRIBUTE
static String	ERROR_MESSAGE_ATTRIBUTE
static String	ERROR_REQUEST_URI_ATTRIBUTE
static String	ERROR_SERVLET_NAME_ATTRIBUTE
static String	ERROR_STATUS_CODE_ATTRIBUTE Standard Servlet 2.3+ spec request attributes for error pages.
static String	FORWARD_CONTEXT_PATH_ATTRIBUTE
static String	FORWARD_PATH_INFO_ATTRIBUTE
static String	FORWARD_QUERY_STRING_ATTRIBUTE
static String	FORWARD_REQUEST_URI_ATTRIBUTE Standard Servlet 2.4+ spec request attributes for forward URI and paths.
static String	FORWARD_SERVLET_PATH_ATTRIBUTE
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	INCLUDE_CONTEXT_PATH_ATTRIBUTE
static String	INCLUDE_PATH_INFO_ATTRIBUTE
static String	INCLUDE_QUERY_STRING_ATTRIBUTE
static String	INCLUDE_REQUEST_URI_ATTRIBUTE Standard Servlet 2.3+ spec request attributes for include URI and paths.
static String	INCLUDE_SERVLET_PATH_ATTRIBUTE
static String	SESSION_MUTEX_ATTRIBUTE Key for the mutex session 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	clearErrorRequestAttributes(HttpServletRequest request) Clear the Servlet spec's error attributes as HttpServletRequest attributes under the keys defined in the Servlet 2.3 specification: javax.servlet.error.status_code, javax.servlet.error.exception_type, javax.servlet.error.message, javax.servlet.error.exception, javax.servlet.error.request_uri, javax.servlet.error.servlet_name.
static void	exposeErrorRequestAttributes(HttpServletRequest request, Throwable ex, String servletName) Expose the Servlet spec's error attributes as HttpServletRequest attributes under the keys defined in the Servlet 2.3 specification, for error pages that are rendered directly rather than through the Servlet container's error page resolution: javax.servlet.error.status_code, javax.servlet.error.exception_type, javax.servlet.error.message, javax.servlet.error.exception, javax.servlet.error.request_uri, javax.servlet.error.servlet_name.
static void	exposeForwardRequestAttributes(HttpServletRequest request) Expose the current request URI and paths as HttpServletRequest attributes under the keys defined in the Servlet 2.4 specification, for containers that implement 2.3 or an earlier version of the Servlet API: javax.servlet.forward.request_uri, javax.servlet.forward.context_path, javax.servlet.forward.servlet_path, javax.servlet.forward.path_info, javax.servlet.forward.query_string.
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 String	findParameterValue(Map parameters, String name) Obtain a named parameter from the given request parameters.
static String	findParameterValue(ServletRequest request, String name) Obtain a named parameter from the given request parameters.
static Cookie	getCookie(HttpServletRequest request, String name) Retrieve the first cookie with the given name.
static Boolean	getDefaultHtmlEscape(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 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 int	getTargetPage(ServletRequest request, String paramPrefix, int currentPage) Return the target page specified in the request.
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

INCLUDE_REQUEST_URI_ATTRIBUTE

public static final String INCLUDE_REQUEST_URI_ATTRIBUTE

Standard Servlet 2.3+ spec request attributes for include URI and paths.

If included via a RequestDispatcher, the current resource will see the originating request. Its own URI and paths are exposed as request attributes.

See Also:

Constant Field Values

INCLUDE_CONTEXT_PATH_ATTRIBUTE

public static final String INCLUDE_CONTEXT_PATH_ATTRIBUTE

See Also:

Constant Field Values

INCLUDE_SERVLET_PATH_ATTRIBUTE

public static final String INCLUDE_SERVLET_PATH_ATTRIBUTE

See Also:

Constant Field Values

INCLUDE_PATH_INFO_ATTRIBUTE

public static final String INCLUDE_PATH_INFO_ATTRIBUTE

See Also:

Constant Field Values

INCLUDE_QUERY_STRING_ATTRIBUTE

public static final String INCLUDE_QUERY_STRING_ATTRIBUTE

See Also:

Constant Field Values

FORWARD_REQUEST_URI_ATTRIBUTE

public static final String FORWARD_REQUEST_URI_ATTRIBUTE

Standard Servlet 2.4+ spec request attributes for forward URI and paths.

If forwarded to via a RequestDispatcher, the current resource will see its own URI and paths. The originating URI and paths are exposed as request attributes.

See Also:

Constant Field Values

FORWARD_CONTEXT_PATH_ATTRIBUTE

public static final String FORWARD_CONTEXT_PATH_ATTRIBUTE

See Also:

Constant Field Values

FORWARD_SERVLET_PATH_ATTRIBUTE

public static final String FORWARD_SERVLET_PATH_ATTRIBUTE

See Also:

Constant Field Values

FORWARD_PATH_INFO_ATTRIBUTE

public static final String FORWARD_PATH_INFO_ATTRIBUTE

See Also:

Constant Field Values

FORWARD_QUERY_STRING_ATTRIBUTE

public static final String FORWARD_QUERY_STRING_ATTRIBUTE

See Also:

Constant Field Values

ERROR_STATUS_CODE_ATTRIBUTE

public static final String ERROR_STATUS_CODE_ATTRIBUTE

Standard Servlet 2.3+ spec request attributes for error pages.

To be exposed to JSPs that are marked as error pages, when forwarding to them directly rather than through the servlet container's error page resolution mechanism.

See Also:

Constant Field Values

ERROR_EXCEPTION_TYPE_ATTRIBUTE

public static final String ERROR_EXCEPTION_TYPE_ATTRIBUTE

See Also:

Constant Field Values

ERROR_MESSAGE_ATTRIBUTE

public static final String ERROR_MESSAGE_ATTRIBUTE

See Also:

Constant Field Values

ERROR_EXCEPTION_ATTRIBUTE

public static final String ERROR_EXCEPTION_ATTRIBUTE

See Also:

Constant Field Values

ERROR_REQUEST_URI_ATTRIBUTE

public static final String ERROR_REQUEST_URI_ATTRIBUTE

See Also:

Constant Field Values

ERROR_SERVLET_NAME_ATTRIBUTE

public static final String ERROR_SERVLET_NAME_ATTRIBUTE

See Also:

Constant Field Values

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

Key for the mutex session 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). Falls back to false in case of no explicit default given.

Parameters:

servletContext - the servlet context of the web application

Returns:

whether default HTML escaping is enabled (default is false)

getDefaultHtmlEscape

public static Boolean getDefaultHtmlEscape(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).

This method differentiates between no param specified at all and an actual boolean value specified, allowing to have a context-specific default in case of no setting at the global level.

Parameters:

servletContext - the servlet context of the web application

Returns:

whether default HTML escaping is enabled (null = no explicit default)

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

path - the path within 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

value - the value 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

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

Returns:

whether the given request is an include request

exposeForwardRequestAttributes

public static void exposeForwardRequestAttributes(HttpServletRequest request)

Expose the current request URI and paths as HttpServletRequest attributes under the keys defined in the Servlet 2.4 specification, for containers that implement 2.3 or an earlier version of the Servlet API: javax.servlet.forward.request_uri, javax.servlet.forward.context_path, javax.servlet.forward.servlet_path, javax.servlet.forward.path_info, javax.servlet.forward.query_string.

Does not override values if already present, to not cause conflicts with the attributes exposed by Servlet 2.4+ containers themselves.

Parameters:

request - current servlet request

exposeErrorRequestAttributes

public static void exposeErrorRequestAttributes(HttpServletRequest request,
                                                Throwable ex,
                                                String servletName)

Expose the Servlet spec's error attributes as HttpServletRequest attributes under the keys defined in the Servlet 2.3 specification, for error pages that are rendered directly rather than through the Servlet container's error page resolution: javax.servlet.error.status_code, javax.servlet.error.exception_type, javax.servlet.error.message, javax.servlet.error.exception, javax.servlet.error.request_uri, javax.servlet.error.servlet_name.

Does not override values if already present, to respect attribute values that have been exposed explicitly before.

Exposes status code 200 by default. Set the "javax.servlet.error.status_code" attribute explicitly (before or after) in order to expose a different status code.

Parameters:

request - current servlet request

ex - the exception encountered

servletName - the name of the offending servlet

clearErrorRequestAttributes

public static void clearErrorRequestAttributes(HttpServletRequest request)

Clear the Servlet spec's error attributes as HttpServletRequest attributes under the keys defined in the Servlet 2.3 specification: javax.servlet.error.status_code, javax.servlet.error.exception_type, javax.servlet.error.message, javax.servlet.error.exception, javax.servlet.error.request_uri, javax.servlet.error.servlet_name.

Parameters:

request - current servlet request

exposeRequestAttributes

public 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. Keys need to be Strings.

Parameters:

request - current HTTP request

attributes - the attributes 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:

request - current servlet request

name - cookie name

Returns:

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

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

findParameterValue

public static String findParameterValue(ServletRequest request,
                                        String name)

Obtain a named parameter from the given request parameters.

See findParameterValue(java.util.Map, String) for a description of the lookup algorithm.

Parameters:

request - current HTTP request

name - the logical name of the request parameter

Returns:

the value of the parameter, or null if the parameter does not exist in given request

findParameterValue

public static String findParameterValue(Map parameters,
                                        String name)

Obtain a named parameter from the given request parameters.

This method will try to obtain a parameter value using the following algorithm:

1. Try to get the parameter value using just the given logical name. This handles parameters of the form logicalName = value. For normal parameters, e.g. submitted using a hidden HTML form field, this will return the requested value.
2. Try to obtain the parameter value from the parameter name, where the parameter name in the request is of the form logicalName_value = xyz with "_" being the configured delimiter. This deals with parameter values submitted using an HTML form submit button.
3. If the value obtained in the previous step has a ".x" or ".y" suffix, remove that. This handles cases where the value was submitted using an HTML form image button. In this case the parameter in the request would actually be of the form logicalName_value.x = 123.

Parameters:

parameters - the available parameter map

name - the logical name of the request parameter

Returns:

the value of the parameter, or null if the parameter does not exist in given request

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.

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()

getTargetPage

public static int getTargetPage(ServletRequest request,
                                String paramPrefix,
                                int currentPage)

Return the target page specified in the request.

Parameters:

request - current servlet request

paramPrefix - the parameter prefix to check for (e.g. "_target" for parameters like "_target1" or "_target2")

currentPage - the current page, to be returned as fallback if no target page specified

Returns:

the page specified in the request, or current page if not found

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")