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Spring Framework example source code file (WebUtils.java)

This example Spring Framework source code file (WebUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

default_web_app_root_key, file, http, httpsession, illegalargumentexception, illegalstateexception, io, map, object, object, request, request, response, servlet, servletcontext, servletcontext, string, string, util

The Spring Framework WebUtils.java source code

/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.util;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;

import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Miscellaneous utilities for web applications.
 * Used by various framework classes.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 */
public abstract class WebUtils {

	/**
	 * Standard Servlet 2.3+ spec request attributes for include URI and paths.
	 * <p>If included via a RequestDispatcher, the current resource will see the
	 * originating request. Its own URI and paths are exposed as request attributes.
	 */
	public static final String INCLUDE_REQUEST_URI_ATTRIBUTE = "javax.servlet.include.request_uri";
	public static final String INCLUDE_CONTEXT_PATH_ATTRIBUTE = "javax.servlet.include.context_path";
	public static final String INCLUDE_SERVLET_PATH_ATTRIBUTE = "javax.servlet.include.servlet_path";
	public static final String INCLUDE_PATH_INFO_ATTRIBUTE = "javax.servlet.include.path_info";
	public static final String INCLUDE_QUERY_STRING_ATTRIBUTE = "javax.servlet.include.query_string";

	/**
	 * Standard Servlet 2.4+ spec request attributes for forward URI and paths.
	 * <p>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.
	 */
	public static final String FORWARD_REQUEST_URI_ATTRIBUTE = "javax.servlet.forward.request_uri";
	public static final String FORWARD_CONTEXT_PATH_ATTRIBUTE = "javax.servlet.forward.context_path";
	public static final String FORWARD_SERVLET_PATH_ATTRIBUTE = "javax.servlet.forward.servlet_path";
	public static final String FORWARD_PATH_INFO_ATTRIBUTE = "javax.servlet.forward.path_info";
	public static final String FORWARD_QUERY_STRING_ATTRIBUTE = "javax.servlet.forward.query_string";


	/**
	 * Prefix of the charset clause in a content type String: ";charset="
	 */
	public static final String CONTENT_TYPE_CHARSET_PREFIX = ";charset=";

	/**
	 * Default character encoding to use when <code>request.getCharacterEncoding
	 * returns <code>null, according to the Servlet spec.
	 * @see ServletRequest#getCharacterEncoding
	 */
	public static final String DEFAULT_CHARACTER_ENCODING = "ISO-8859-1";

	/**
	 * Standard Servlet spec context attribute that specifies a temporary
	 * directory for the current web application, of type <code>java.io.File.
	 */
	public static final String TEMP_DIR_CONTEXT_ATTRIBUTE = "javax.servlet.context.tempdir";

	/**
	 * HTML escape parameter at the servlet context level
	 * (i.e. a context-param in <code>web.xml): "defaultHtmlEscape".
	 */
	public static final String HTML_ESCAPE_CONTEXT_PARAM = "defaultHtmlEscape";

	/**
	 * Web app root key parameter at the servlet context level
	 * (i.e. a context-param in <code>web.xml): "webAppRootKey".
	 */
	public static final String WEB_APP_ROOT_KEY_PARAM = "webAppRootKey";

	/** Default web app root key: "webapp.root" */
	public static final String DEFAULT_WEB_APP_ROOT_KEY = "webapp.root";

	/** Name suffixes in case of image buttons */
	public static final String[] SUBMIT_IMAGE_SUFFIXES = {".x", ".y"};

	/** Key for the mutex session attribute */
	public static final String SESSION_MUTEX_ATTRIBUTE = WebUtils.class.getName() + ".MUTEX";


	/**
	 * 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 <code>web.xml. Default is "webapp.root".
	 * <p>Can be used for tools that support substition with System.getProperty
	 * values, like log4j's "${key}" syntax within log file locations.
	 * @param 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 #WEB_APP_ROOT_KEY_PARAM
	 * @see #DEFAULT_WEB_APP_ROOT_KEY
	 * @see WebAppRootListener
	 * @see Log4jWebConfigurer
	 */
	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 + "]");
	}

	/**
	 * Remove the system property that points to the web app root directory.
	 * To be called on shutdown of the web application.
	 * @param servletContext the servlet context of the web application
	 * @see #setWebAppRootSystemProperty
	 */
	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);
	}

	/**
	 * Return whether default HTML escaping is enabled for the web application,
	 * i.e. the value of the "defaultHtmlEscape" context-param in <code>web.xml
	 * (if any). Falls back to <code>false in case of no explicit default given.
	 * @param servletContext the servlet context of the web application
	 * @return whether default HTML escaping is enabled (default is false)
	 */
	public static boolean isDefaultHtmlEscape(ServletContext servletContext) {
		if (servletContext == null) {
			return false;
		}
		String param = servletContext.getInitParameter(HTML_ESCAPE_CONTEXT_PARAM);
		return Boolean.valueOf(param).booleanValue();
	}

	/**
	 * Return whether default HTML escaping is enabled for the web application,
	 * i.e. the value of the "defaultHtmlEscape" context-param in <code>web.xml
	 * (if any).
	 * <p>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.
	 * @param servletContext the servlet context of the web application
	 * @return whether default HTML escaping is enabled (null = no explicit default)
	 */
	public static Boolean getDefaultHtmlEscape(ServletContext servletContext) {
		if (servletContext == null) {
			return null;
		}
		Assert.notNull(servletContext, "ServletContext must not be null");
		String param = servletContext.getInitParameter(HTML_ESCAPE_CONTEXT_PARAM);
		return (StringUtils.hasText(param)? Boolean.valueOf(param) : null);
	}

	/**
	 * Return the temporary directory for the current web application,
	 * as provided by the servlet container.
	 * @param servletContext the servlet context of the web application
	 * @return the File representing the temporary directory
	 */
	public static File getTempDir(ServletContext servletContext) {
		Assert.notNull(servletContext, "ServletContext must not be null");
		return (File) servletContext.getAttribute(TEMP_DIR_CONTEXT_ATTRIBUTE);
	}

	/**
	 * Return the real path of the given path within the web application,
	 * as provided by the servlet container.
	 * <p>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 <code>getRealPath,
	 * which returns null).
	 * @param servletContext the servlet context of the web application
	 * @param path the path within the web application
	 * @return the corresponding real path
	 * @throws FileNotFoundException if the path cannot be resolved to a resource
	 * @see javax.servlet.ServletContext#getRealPath
	 */
	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;
	}


	/**
	 * Determine the session id of the given request, if any.
	 * @param request current HTTP request
	 * @return the session id, or <code>null if none
	 */
	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);
	}

	/**
	 * 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 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);
	}

	/**
	 * 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 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;
	}

	/**
	 * 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);
			}
		}
	}

	/**
	 * 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.
	 * @param session current HTTP session
	 * @param name the name of the session attribute
	 * @param clazz the class to instantiate for a new attribute
	 * @return the value of the session attribute, newly created if not found
	 * @throws IllegalArgumentException if the session attribute could not be instantiated
	 */
	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;
	}

	/**
	 * Return the best available mutex for the given session:
	 * that is, an object to synchronize on for the given session.
	 * <p>Returns the session mutex attribute if available; usually,
	 * this means that the HttpSessionMutexListener needs to be defined
	 * in <code>web.xml. Falls back to the HttpSession itself
	 * if no mutex attribute found.
	 * <p>The session mutex is guaranteed to be the same object during
	 * the entire lifetime of the session, available under the key defined
	 * by the <code>SESSION_MUTEX_ATTRIBUTE constant. It serves as a
	 * safe reference to synchronize on for locking on the current session.
	 * <p>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.
	 * @param session the HttpSession to find a mutex for
	 * @return the mutex object (never <code>null)
	 * @see #SESSION_MUTEX_ATTRIBUTE
	 * @see HttpSessionMutexListener
	 */
	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;
	}


	/**
	 * Determine whether the given request is an include request,
	 * that is, not a top-level HTTP request coming in from the outside.
	 * <p>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.
	 * @param request current servlet request
	 * @return whether the given request is an include request
	 */
	public static boolean isIncludeRequest(ServletRequest request) {
		return (request.getAttribute(INCLUDE_REQUEST_URI_ATTRIBUTE) != null);
	}

	/**
	 * Expose the current request URI and paths as {@link javax.servlet.http.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:
	 * <code>javax.servlet.forward.request_uri,
	 * <code>javax.servlet.forward.context_path,
	 * <code>javax.servlet.forward.servlet_path,
	 * <code>javax.servlet.forward.path_info,
	 * <code>javax.servlet.forward.query_string.
	 * <p>Does not override values if already present, to not cause conflicts
	 * with the attributes exposed by Servlet 2.4+ containers themselves.
	 * @param request current servlet request
	 */
	public static void exposeForwardRequestAttributes(HttpServletRequest request) {
		if (request.getAttribute(FORWARD_REQUEST_URI_ATTRIBUTE) == null) {
			request.setAttribute(FORWARD_REQUEST_URI_ATTRIBUTE, request.getRequestURI());
		}
		if (request.getAttribute(FORWARD_CONTEXT_PATH_ATTRIBUTE) == null) {
			request.setAttribute(FORWARD_CONTEXT_PATH_ATTRIBUTE, request.getContextPath());
		}
		if (request.getAttribute(FORWARD_SERVLET_PATH_ATTRIBUTE) == null) {
			request.setAttribute(FORWARD_SERVLET_PATH_ATTRIBUTE, request.getServletPath());
		}
		if (request.getAttribute(FORWARD_PATH_INFO_ATTRIBUTE) == null) {
			request.setAttribute(FORWARD_PATH_INFO_ATTRIBUTE, request.getPathInfo());
		}
		if (request.getAttribute(FORWARD_QUERY_STRING_ATTRIBUTE) == null) {
			request.setAttribute(FORWARD_QUERY_STRING_ATTRIBUTE, request.getQueryString());
		}
	}

	/**
	 * 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");
		Iterator it = attributes.entrySet().iterator();
		while (it.hasNext()) {
			Map.Entry entry = (Map.Entry) it.next();
			if (!(entry.getKey() instanceof String)) {
				throw new IllegalArgumentException(
						"Invalid key [" + entry.getKey() + "] in attributes Map - only Strings allowed as attribute keys");
			}
			request.setAttribute((String) entry.getKey(), entry.getValue());
		}
	}

	/**
	 * 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 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 (int i = 0; i < cookies.length; i++) {
				if (name.equals(cookies[i].getName())) {
					return cookies[i];
				}
			}
		}
		return null;
	}


	/**
	 * 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").
	 * @param request current HTTP request
	 * @param name name of the parameter
	 * @return if the parameter was sent
	 * @see #SUBMIT_IMAGE_SUFFIXES
	 */
	public static boolean hasSubmitParameter(ServletRequest request, String name) {
		Assert.notNull(request, "Request must not be null");
		if (request.getParameter(name) != null) {
			return true;
		}
		for (int i = 0; i < SUBMIT_IMAGE_SUFFIXES.length; i++) {
			String suffix = SUBMIT_IMAGE_SUFFIXES[i];
			if (request.getParameter(name + suffix) != null) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Return a map containing all parameters with the given prefix.
	 * Maps single values to String and multiple values to String array.
	 * <p>For example, with a prefix of "spring_", "spring_param1" and
	 * "spring_param2" result in a Map with "param1" and "param2" as keys.
	 * @param request HTTP request in which to look for parameters
	 * @param prefix the beginning of parameter names
	 * (if this is null or the empty string, all parameters will match)
	 * @return map containing request parameters <b>without the prefix,
	 * containing either a String or a String array as values
	 * @see javax.servlet.ServletRequest#getParameterNames
	 * @see javax.servlet.ServletRequest#getParameterValues
	 * @see javax.servlet.ServletRequest#getParameterMap
	 */
	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 = (String) 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;
	}

	/**
	 * Return the target page specified in the request.
	 * @param request current servlet request
	 * @param paramPrefix the parameter prefix to check for
	 * (e.g. "_target" for parameters like "_target1" or "_target2")
	 * @param currentPage the current page, to be returned as fallback
	 * if no target page specified
	 * @return the page specified in the request, or current page if not found
	 */
	public static int getTargetPage(ServletRequest request, String paramPrefix, int currentPage) {
		Enumeration paramNames = request.getParameterNames();
		while (paramNames.hasMoreElements()) {
			String paramName = (String) 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;
	}


	/**
	 * 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) {
		int begin = urlPath.lastIndexOf('/') + 1;
		int end = urlPath.indexOf(';');
		if (end == -1) {
			end = urlPath.indexOf('?');
			if (end == -1) {
				end = urlPath.length();
			}
		}
		String filename = urlPath.substring(begin, end);
		int dotIndex = filename.lastIndexOf('.');
		if (dotIndex != -1) {
			filename = filename.substring(0, dotIndex);
		}
		return filename;
	}

}

Other Spring Framework examples (source code examples)

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