今天本來是看shiro框架和spring等框架的整合，順帶看了一下web.xml的配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
	version="3.0">
	<display-name>Mi Shopkeeper</display-name>
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:spring.xml</param-value>
	</context-param>
	<listener>
		<listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>
	</listener>
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
	<listener>  
        <listener-class>com.im.cashier.validator.SessionListener</listener-class>          
	</listener>  
	
	<filter>
		<filter-name>springUtf8Encoding</filter-name>
		<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
		<init-param>
			<param-name>encoding</param-name>
			<param-value>UTF-8</param-value>
		</init-param>
		<init-param>
			<param-name>forceEncoding</param-name>
			<param-value>true</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>springUtf8Encoding</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
 

	
	<filter>
		<filter-name>shiroFilter</filter-name>
		<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
		<init-param>
			<param-name>targetFilterLifecycle</param-name>
			<param-value>true</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>shiroFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
		
	

	<servlet>
		<servlet-name>spring</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>classpath:spring-mvc.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>spring</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
</web-app>
 

/*
 * Copyright 2002-2016 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.filter;

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.util.Assert;

/**
 * Servlet Filter that allows one to specify a character encoding for requests.
 * This is useful because current browsers typically do not set a character
 * encoding even if specified in the HTML page or form.
 *
 * <p>This filter can either apply its encoding if the request does not already
 * specify an encoding, or enforce this filter's encoding in any case
 * ("forceEncoding"="true"). In the latter case, the encoding will also be
 * applied as default response encoding (although this will usually be overridden
 * by a full content type set in the view).
 *
 * @author Juergen Hoeller
 * @since 15.03.2004
 * @see #setEncoding
 * @see #setForceEncoding
 * @see javax.servlet.http.HttpServletRequest#setCharacterEncoding
 * @see javax.servlet.http.HttpServletResponse#setCharacterEncoding
 */
public class CharacterEncodingFilter extends OncePerRequestFilter
 
 {

	private String encoding;

	private boolean forceRequestEncoding = false;

	private boolean forceResponseEncoding = false;


	/**
	 * Create a default {@code CharacterEncodingFilter},
	 * with the encoding to be set via {@link #setEncoding}.
	 * @see #setEncoding
	 */
	public CharacterEncodingFilter() {
	}

	/**
	 * Create a {@code CharacterEncodingFilter} for the given encoding.
	 * @param encoding the encoding to apply
	 * @since 4.2.3
	 * @see #setEncoding
	 */
	public CharacterEncodingFilter(String encoding) {
		this(encoding, false);
	}

	/**
	 * Create a {@code CharacterEncodingFilter} for the given encoding.
	 * @param encoding the encoding to apply
	 * @param forceEncoding whether the specified encoding is supposed to
	 * override existing request and response encodings
	 * @since 4.2.3
	 * @see #setEncoding
	 * @see #setForceEncoding
	 */
	public CharacterEncodingFilter(String encoding, boolean forceEncoding) {
		this(encoding, forceEncoding, forceEncoding);
	}

	/**
	 * Create a {@code CharacterEncodingFilter} for the given encoding.
	 * @param encoding the encoding to apply
	 * @param forceRequestEncoding whether the specified encoding is supposed to
	 * override existing request encodings
	 * @param forceResponseEncoding whether the specified encoding is supposed to
	 * override existing response encodings
	 * @since 4.3
	 * @see #setEncoding
	 * @see #setForceRequestEncoding(boolean)
	 * @see #setForceResponseEncoding(boolean)
	 */
	public CharacterEncodingFilter(String encoding, boolean forceRequestEncoding, boolean forceResponseEncoding) {
		Assert.hasLength(encoding, "Encoding must not be empty");
		this.encoding = encoding;
		this.forceRequestEncoding = forceRequestEncoding;
		this.forceResponseEncoding = forceResponseEncoding;
	}


	/**
	 * Set the encoding to use for requests. This encoding will be passed into a
	 * {@link javax.servlet.http.HttpServletRequest#setCharacterEncoding} call.
	 * <p>Whether this encoding will override existing request encodings
	 * (and whether it will be applied as default response encoding as well)
	 * depends on the {@link #setForceEncoding "forceEncoding"} flag.
	 */
	public void setEncoding(String encoding) {
		this.encoding = encoding;
	}

	/**
	 * Return the configured encoding for requests and/or responses
	 * @since 4.3
	 */
	public String getEncoding() {
		return this.encoding;
	}

	/**
	 * Set whether the configured {@link #setEncoding encoding} of this filter
	 * is supposed to override existing request and response encodings.
	 * <p>Default is "false", i.e. do not modify the encoding if
	 * {@link javax.servlet.http.HttpServletRequest#getCharacterEncoding()}
	 * returns a non-null value. Switch this to "true" to enforce the specified
	 * encoding in any case, applying it as default response encoding as well.
	 * <p>This is the equivalent to setting both {@link #setForceRequestEncoding(boolean)}
	 * and {@link #setForceResponseEncoding(boolean)}.
	 * @see #setForceRequestEncoding(boolean)
	 * @see #setForceResponseEncoding(boolean)
	 */
	public void setForceEncoding(boolean forceEncoding) {
		this.forceRequestEncoding = forceEncoding;
		this.forceResponseEncoding = forceEncoding;
	}

	/**
	 * Set whether the configured {@link #setEncoding encoding} of this filter
	 * is supposed to override existing request encodings.
	 * <p>Default is "false", i.e. do not modify the encoding if
	 * {@link javax.servlet.http.HttpServletRequest#getCharacterEncoding()}
	 * returns a non-null value. Switch this to "true" to enforce the specified
	 * encoding in any case.
	 * @since 4.3
	 */
	public void setForceRequestEncoding(boolean forceRequestEncoding) {
		this.forceRequestEncoding = forceRequestEncoding;
	}

	/**
	 * Return whether the encoding should be forced on requests
	 * @since 4.3
	 */
	public boolean isForceRequestEncoding() {
		return this.forceRequestEncoding;
	}

	/**
	 * Set whether the configured {@link #setEncoding encoding} of this filter
	 * is supposed to override existing response encodings.
	 * <p>Default is "false", i.e. do not modify the encoding.
	 * Switch this to "true" to enforce the specified encoding
	 * for responses in any case.
	 * @since 4.3
	 */
	public void setForceResponseEncoding(boolean forceResponseEncoding) {
		this.forceResponseEncoding = forceResponseEncoding;
	}

	/**
	 * Return whether the encoding should be forced on responses.
	 * @since 4.3
	 */
	public boolean isForceResponseEncoding() {
		return this.forceResponseEncoding;
	}


	@Override
	protected void doFilterInternal(
			HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		String encoding = getEncoding();
		if (encoding != null) {
			if (isForceRequestEncoding() || request.getCharacterEncoding() == null) {
				request.setCharacterEncoding(encoding);
			}
			if (isForceResponseEncoding()) {
				response.setCharacterEncoding(encoding);
			}
		}
		filterChain.doFilter(request, response);
	}

}

OncePerRequestFilter原始碼我記得，shiro中好像也有這一出

/*
 * Copyright 2002-2015 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.filter;

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.context.request.async.WebAsyncManager;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.util.WebUtils;

/**
 * Filter base class that aims to guarantee a single execution per request
 * dispatch, on any servlet container. It provides a {@link #doFilterInternal}
 * method with HttpServletRequest and HttpServletResponse arguments.
 *
 * <p>As of Servlet 3.0, a filter may be invoked as part of a
 * {@link javax.servlet.DispatcherType#REQUEST REQUEST} or
 * {@link javax.servlet.DispatcherType#ASYNC ASYNC} dispatches that occur in
 * separate threads. A filter can be configured in {@code web.xml} whether it
 * should be involved in async dispatches. However, in some cases servlet
 * containers assume different default configuration. Therefore sub-classes can
 * override the method {@link #shouldNotFilterAsyncDispatch()} to declare
 * statically if they should indeed be invoked, <em>once</em>, during both types
 * of dispatches in order to provide thread initialization, logging, security,
 * and so on. This mechanism complements and does not replace the need to
 * configure a filter in {@code web.xml} with dispatcher types.
 *
 * <p>Subclasses may use {@link #isAsyncDispatch(HttpServletRequest)} to
 * determine when a filter is invoked as part of an async dispatch, and use
 * {@link #isAsyncStarted(HttpServletRequest)} to determine when the request
 * has been placed in async mode and therefore the current dispatch won't be
 * the last one for the given request.
 *
 * <p>Yet another dispatch type that also occurs in its own thread is
 * {@link javax.servlet.DispatcherType#ERROR ERROR}. Subclasses can override
 * {@link #shouldNotFilterErrorDispatch()} if they wish to declare statically
 * if they should be invoked <em>once</em> during error dispatches.
 *
 * <p>The {@link #getAlreadyFilteredAttributeName} method determines how to
 * identify that a request is already filtered. The default implementation is
 * based on the configured name of the concrete filter instance.
 *
 * @author Juergen Hoeller
 * @author Rossen Stoyanchev
 * @since 06.12.2003
 */
public abstract class OncePerRequestFilter extends GenericFilterBean {

	/**
	 * Suffix that gets appended to the filter name for the
	 * "already filtered" request attribute.
	 * @see #getAlreadyFilteredAttributeName
	 */
	public static final String ALREADY_FILTERED_SUFFIX = ".FILTERED";


	/**
	 * This {@code doFilter} implementation stores a request attribute for
	 * "already filtered", proceeding without filtering again if the
	 * attribute is already there.
	 * @see #getAlreadyFilteredAttributeName
	 * @see #shouldNotFilter
	 * @see #doFilterInternal
	 */
	@Override
	public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {
			throw new ServletException("OncePerRequestFilter just supports HTTP requests");
		}
		HttpServletRequest httpRequest = (HttpServletRequest) request;
		HttpServletResponse httpResponse = (HttpServletResponse) response;

		String alreadyFilteredAttributeName = getAlreadyFilteredAttributeName();
		boolean hasAlreadyFilteredAttribute = request.getAttribute(alreadyFilteredAttributeName) != null;

		if (hasAlreadyFilteredAttribute || skipDispatch(httpRequest) || shouldNotFilter(httpRequest)) {

			// Proceed without invoking this filter...
			filterChain.doFilter(request, response);
		}
		else {
			// Do invoke this filter...
			request.setAttribute(alreadyFilteredAttributeName, Boolean.TRUE);
			try {
				doFilterInternal(httpRequest, httpResponse, filterChain);
			}
			finally {
				// Remove the "already filtered" request attribute for this request.
				request.removeAttribute(alreadyFilteredAttributeName);
			}
		}
	}


	private boolean skipDispatch(HttpServletRequest request) {
		if (isAsyncDispatch(request) && shouldNotFilterAsyncDispatch()) {
			return true;
		}
		if (request.getAttribute(WebUtils.ERROR_REQUEST_URI_ATTRIBUTE) != null && shouldNotFilterErrorDispatch()) {
			return true;
		}
		return false;
	}

	/**
	 * The dispatcher type {@code javax.servlet.DispatcherType.ASYNC} introduced
	 * in Servlet 3.0 means a filter can be invoked in more than one thread over
	 * the course of a single request. This method returns {@code true} if the
	 * filter is currently executing within an asynchronous dispatch.
	 * @param request the current request
	 * @since 3.2
	 * @see WebAsyncManager#hasConcurrentResult()
	 */
	protected boolean isAsyncDispatch(HttpServletRequest request) {
		return WebAsyncUtils.getAsyncManager(request).hasConcurrentResult();
	}

	/**
	 * Whether request processing is in asynchronous mode meaning that the
	 * response will not be committed after the current thread is exited.
	 * @param request the current request
	 * @since 3.2
	 * @see WebAsyncManager#isConcurrentHandlingStarted()
	 */
	protected boolean isAsyncStarted(HttpServletRequest request) {
		return WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted();
	}

	/**
	 * Return the name of the request attribute that identifies that a request
	 * is already filtered.
	 * <p>The default implementation takes the configured name of the concrete filter
	 * instance and appends ".FILTERED". If the filter is not fully initialized,
	 * it falls back to its class name.
	 * @see #getFilterName
	 * @see #ALREADY_FILTERED_SUFFIX
	 */
	protected String getAlreadyFilteredAttributeName() {
		String name = getFilterName();
		if (name == null) {
			name = getClass().getName();
		}
		return name + ALREADY_FILTERED_SUFFIX;
	}

	/**
	 * Can be overridden in subclasses for custom filtering control,
	 * returning {@code true} to avoid filtering of the given request.
	 * <p>The default implementation always returns {@code false}.
	 * @param request current HTTP request
	 * @return whether the given request should <i>not</i> be filtered
	 * @throws ServletException in case of errors
	 */
	protected boolean shouldNotFilter(HttpServletRequest request) throws ServletException {
		return false;
	}

	/**
	 * The dispatcher type {@code javax.servlet.DispatcherType.ASYNC} introduced
	 * in Servlet 3.0 means a filter can be invoked in more than one thread
	 * over the course of a single request. Some filters only need to filter
	 * the initial thread (e.g. request wrapping) while others may need
	 * to be invoked at least once in each additional thread for example for
	 * setting up thread locals or to perform final processing at the very end.
	 * <p>Note that although a filter can be mapped to handle specific dispatcher
	 * types via {@code web.xml} or in Java through the {@code ServletContext},
	 * servlet containers may enforce different defaults with regards to
	 * dispatcher types. This flag enforces the design intent of the filter.
	 * <p>The default return value is "true", which means the filter will not be
	 * invoked during subsequent async dispatches. If "false", the filter will
	 * be invoked during async dispatches with the same guarantees of being
	 * invoked only once during a request within a single thread.
	 * @since 3.2
	 */
	protected boolean shouldNotFilterAsyncDispatch() {
		return true;
	}

	/**
	 * Whether to filter error dispatches such as when the servlet container
	 * processes and error mapped in {@code web.xml}. The default return value
	 * is "true", which means the filter will not be invoked in case of an error
	 * dispatch.
	 * @since 3.2
	 */
	protected boolean shouldNotFilterErrorDispatch() {
		return true;
	}


	/**
	 * Same contract as for {@code doFilter}, but guaranteed to be
	 * just invoked once per request within a single request thread.
	 * See {@link #shouldNotFilterAsyncDispatch()} for details.
	 * <p>Provides HttpServletRequest and HttpServletResponse arguments instead of the
	 * default ServletRequest and ServletResponse ones.
	 */
	protected abstract void doFilterInternal(
			HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException;

}

/*
 * Copyright 2002-2012 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.filter;

import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;
import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeansException;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyAccessorFactory;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.EnvironmentAware;
import org.springframework.core.env.Environment;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceEditor;
import org.springframework.core.io.ResourceLoader;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.web.context.ServletContextAware;
import org.springframework.web.context.support.ServletContextResourceLoader;
import org.springframework.web.context.support.StandardServletEnvironment;
import org.springframework.web.util.NestedServletException;

/**
 * Simple base implementation of {@link javax.servlet.Filter} which treats
 * its config parameters ({@code init-param} entries within the
 * {@code filter} tag in {@code web.xml}) as bean properties.
 *
 * <p>A handy superclass for any type of filter. Type conversion of config
 * parameters is automatic, with the corresponding setter method getting
 * invoked with the converted value. It is also possible for subclasses to
 * specify required properties. Parameters without matching bean property
 * setter will simply be ignored.
 *
 * <p>This filter leaves actual filtering to subclasses, which have to
 * implement the {@link javax.servlet.Filter#doFilter} method.
 *
 * <p>This generic filter base class has no dependency on the Spring
 * {@link org.springframework.context.ApplicationContext} concept.
 * Filters usually don't load their own context but rather access service
 * beans from the Spring root application context, accessible via the
 * filter's {@link #getServletContext() ServletContext} (see
 * {@link org.springframework.web.context.support.WebApplicationContextUtils}).
 *
 * @author Juergen Hoeller
 * @since 06.12.2003
 * @see #addRequiredProperty
 * @see #initFilterBean
 * @see #doFilter
 */
public abstract class GenericFilterBean implements
		Filter, BeanNameAware, EnvironmentAware, ServletContextAware, InitializingBean, DisposableBean {

	/** Logger available to subclasses */
	protected final Log logger = LogFactory.getLog(getClass());

	/**
	 * Set of required properties (Strings) that must be supplied as
	 * config parameters to this filter.
	 */
	private final Set<String> requiredProperties = new HashSet<String>();

	private FilterConfig filterConfig;

	private String beanName;

	private Environment environment = new StandardServletEnvironment();

	private ServletContext servletContext;


	/**
	 * Stores the bean name as defined in the Spring bean factory.
	 * <p>Only relevant in case of initialization as bean, to have a name as
	 * fallback to the filter name usually provided by a FilterConfig instance.
	 * @see org.springframework.beans.factory.BeanNameAware
	 * @see #getFilterName()
	 */
	@Override
	public final void setBeanName(String beanName) {
		this.beanName = beanName;
	}

	/**
	 * {@inheritDoc}
	 * <p>Any environment set here overrides the {@link StandardServletEnvironment}
	 * provided by default.
	 * <p>This {@code Environment} object is used only for resolving placeholders in
	 * resource paths passed into init-parameters for this filter. If no init-params are
	 * used, this {@code Environment} can be essentially ignored.
	 * @see #init(FilterConfig)
	 */
	@Override
	public void setEnvironment(Environment environment) {
		this.environment = environment;
	}

	/**
	 * Stores the ServletContext that the bean factory runs in.
	 * <p>Only relevant in case of initialization as bean, to have a ServletContext
	 * as fallback to the context usually provided by a FilterConfig instance.
	 * @see org.springframework.web.context.ServletContextAware
	 * @see #getServletContext()
	 */
	@Override
	public final void setServletContext(ServletContext servletContext) {
		this.servletContext = servletContext;
	}

	/**
	 * Calls the {@code initFilterBean()} method that might
	 * contain custom initialization of a subclass.
	 * <p>Only relevant in case of initialization as bean, where the
	 * standard {@code init(FilterConfig)} method won't be called.
	 * @see #initFilterBean()
	 * @see #init(javax.servlet.FilterConfig)
	 */
	@Override
	public void afterPropertiesSet() throws ServletException {
		initFilterBean();
	}


	/**
	 * Subclasses can invoke this method to specify that this property
	 * (which must match a JavaBean property they expose) is mandatory,
	 * and must be supplied as a config parameter. This should be called
	 * from the constructor of a subclass.
	 * <p>This method is only relevant in case of traditional initialization
	 * driven by a FilterConfig instance.
	 * @param property name of the required property
	 */
	protected final void addRequiredProperty(String property) {
		this.requiredProperties.add(property);
	}

	/**
	 * Standard way of initializing this filter.
	 * Map config parameters onto bean properties of this filter, and
	 * invoke subclass initialization.
	 * @param filterConfig the configuration for this filter
	 * @throws ServletException if bean properties are invalid (or required
	 * properties are missing), or if subclass initialization fails.
	 * @see #initFilterBean
	 */
	@Override
	public final void init(FilterConfig filterConfig) throws ServletException {
		Assert.notNull(filterConfig, "FilterConfig must not be null");
		if (logger.isDebugEnabled()) {
			logger.debug("Initializing filter '" + filterConfig.getFilterName() + "'");
		}

		this.filterConfig = filterConfig;

		// Set bean properties from init parameters.
		try {
			PropertyValues pvs = new FilterConfigPropertyValues(filterConfig, this.requiredProperties);
			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
			ResourceLoader resourceLoader = new ServletContextResourceLoader(filterConfig.getServletContext());
			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.environment));
			initBeanWrapper(bw);
			bw.setPropertyValues(pvs, true);
		}
		catch (BeansException ex) {
			String msg = "Failed to set bean properties on filter '" +
				filterConfig.getFilterName() + "': " + ex.getMessage();
			logger.error(msg, ex);
			throw new NestedServletException(msg, ex);
		}

		// Let subclasses do whatever initialization they like.
		initFilterBean();

		if (logger.isDebugEnabled()) {
			logger.debug("Filter '" + filterConfig.getFilterName() + "' configured successfully");
		}
	}

	/**
	 * Initialize the BeanWrapper for this GenericFilterBean,
	 * possibly with custom editors.
	 * <p>This default implementation is empty.
	 * @param bw the BeanWrapper to initialize
	 * @throws BeansException if thrown by BeanWrapper methods
	 * @see org.springframework.beans.BeanWrapper#registerCustomEditor
	 */
	protected void initBeanWrapper(BeanWrapper bw) throws BeansException {
	}


	/**
	 * Make the FilterConfig of this filter available, if any.
	 * Analogous to GenericServlet's {@code getServletConfig()}.
	 * <p>Public to resemble the {@code getFilterConfig()} method
	 * of the Servlet Filter version that shipped with WebLogic 6.1.
	 * @return the FilterConfig instance, or {@code null} if none available
	 * @see javax.servlet.GenericServlet#getServletConfig()
	 */
	public final FilterConfig getFilterConfig() {
		return this.filterConfig;
	}

	/**
	 * Make the name of this filter available to subclasses.
	 * Analogous to GenericServlet's {@code getServletName()}.
	 * <p>Takes the FilterConfig's filter name by default.
	 * If initialized as bean in a Spring application context,
	 * it falls back to the bean name as defined in the bean factory.
	 * @return the filter name, or {@code null} if none available
	 * @see javax.servlet.GenericServlet#getServletName()
	 * @see javax.servlet.FilterConfig#getFilterName()
	 * @see #setBeanName
	 */
	protected final String getFilterName() {
		return (this.filterConfig != null ? this.filterConfig.getFilterName() : this.beanName);
	}

	/**
	 * Make the ServletContext of this filter available to subclasses.
	 * Analogous to GenericServlet's {@code getServletContext()}.
	 * <p>Takes the FilterConfig's ServletContext by default.
	 * If initialized as bean in a Spring application context,
	 * it falls back to the ServletContext that the bean factory runs in.
	 * @return the ServletContext instance, or {@code null} if none available
	 * @see javax.servlet.GenericServlet#getServletContext()
	 * @see javax.servlet.FilterConfig#getServletContext()
	 * @see #setServletContext
	 */
	protected final ServletContext getServletContext() {
		return (this.filterConfig != null ? this.filterConfig.getServletContext() : this.servletContext);
	}


	/**
	 * Subclasses may override this to perform custom initialization.
	 * All bean properties of this filter will have been set before this
	 * method is invoked.
	 * <p>Note: This method will be called from standard filter initialization
	 * as well as filter bean initialization in a Spring application context.
	 * Filter name and ServletContext will be available in both cases.
	 * <p>This default implementation is empty.
	 * @throws ServletException if subclass initialization fails
	 * @see #getFilterName()
	 * @see #getServletContext()
	 */
	protected void initFilterBean() throws ServletException {
	}

	/**
	 * Subclasses may override this to perform custom filter shutdown.
	 * <p>Note: This method will be called from standard filter destruction
	 * as well as filter bean destruction in a Spring application context.
	 * <p>This default implementation is empty.
	 */
	@Override
	public void destroy() {
	}


	/**
	 * PropertyValues implementation created from FilterConfig init parameters.
	 */
	@SuppressWarnings("serial")
	private static class FilterConfigPropertyValues extends MutablePropertyValues {

		/**
		 * Create new FilterConfigPropertyValues.
		 * @param config FilterConfig we'll use to take PropertyValues from
		 * @param requiredProperties set of property names we need, where
		 * we can't accept default values
		 * @throws ServletException if any required properties are missing
		 */
		public FilterConfigPropertyValues(FilterConfig config, Set<String> requiredProperties)
			throws ServletException {

			Set<String> missingProps = (requiredProperties != null && !requiredProperties.isEmpty()) ?
					new HashSet<String>(requiredProperties) : null;

			Enumeration<?> en = config.getInitParameterNames();
			while (en.hasMoreElements()) {
				String property = (String) en.nextElement();
				Object value = config.getInitParameter(property);
				addPropertyValue(new PropertyValue(property, value));
				if (missingProps != null) {
					missingProps.remove(property);
				}
			}

			// Fail if we are still missing properties.
			if (missingProps != null && missingProps.size() > 0) {
				throw new ServletException(
					"Initialization from FilterConfig for filter '" + config.getFilterName() +
					"' failed; the following required properties were missing: " +
					StringUtils.collectionToDelimitedString(missingProps, ", "));
			}
		}
	}

}

/*
 * The contents of this file are subject to the terms
 * of the Common Development and Distribution License
 * (the "License").  You may not use this file except
 * in compliance with the License.
 *
 * You can obtain a copy of the license at
 * glassfish/bootstrap/legal/CDDLv1.0.txt or
 * https://glassfish.dev.java.net/public/CDDLv1.0.html.
 * See the License for the specific language governing
 * permissions and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL
 * HEADER in each file and include the License file at
 * glassfish/bootstrap/legal/CDDLv1.0.txt.  If applicable,
 * add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your
 * own identifying information: Portions Copyright [yyyy]
 * [name of copyright owner]
 *
 * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
 *
 * Portions Copyright Apache Software Foundation.
 */

package javax.servlet;

import java.io.IOException;

	/** 
	* A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both.
        * <br><br>
	* Filters perform filtering in the <code>doFilter</code> method. Every Filter has access to 
	** a FilterConfig object from which it can obtain its initialization parameters, a
	** reference to the ServletContext which it can use, for example, to load resources
	** needed for filtering tasks.
	** <p>
	** Filters are configured in the deployment descriptor of a web application
	** <p>
	** Examples that have been identified for this design are<br>
	** 1) Authentication Filters <br>
	** 2) Logging and Auditing Filters <br>
	** 3) Image conversion Filters <br>
    	** 4) Data compression Filters <br>
	** 5) Encryption Filters <br>
	** 6) Tokenizing Filters <br>
	** 7) Filters that trigger resource access events <br>
	** 8) XSL/T filters <br>
	** 9) Mime-type chain Filter <br>
	 * @since	Servlet 2.3
	*/

public interface Filter {

	/** 
	* Called by the web container to indicate to a filter that it is being placed into
	* service. The servlet container calls the init method exactly once after instantiating the
	* filter. The init method must complete successfully before the filter is asked to do any
	* filtering work. <br><br>

     	* The web container cannot place the filter into service if the init method either<br>
        * 1.Throws a ServletException <br>
        * 2.Does not return within a time period defined by the web container 
	*/
	public void init(FilterConfig filterConfig) throws ServletException;
	
	
	/**
	* The <code>doFilter</code> method of the Filter is called by the container
	* each time a request/response pair is passed through the chain due
	* to a client request for a resource at the end of the chain. The FilterChain passed in to this
	* method allows the Filter to pass on the request and response to the next entity in the
	* chain.<p>
	* A typical implementation of this method would follow the following pattern:- <br>
	* 1. Examine the request<br>
	* 2. Optionally wrap the request object with a custom implementation to
	* filter content or headers for input filtering <br>
	* 3. Optionally wrap the response object with a custom implementation to
	* filter content or headers for output filtering <br>
	* 4. a) <strong>Either</strong> invoke the next entity in the chain using the FilterChain object (<code>chain.doFilter()</code>), <br>   
	** 4. b) <strong>or</strong> not pass on the request/response pair to the next entity in the filter chain to block the request processing<br>
	** 5. Directly set headers on the response after invocation of the next entity in the filter chain.
	**/
    public void doFilter ( ServletRequest request, ServletResponse response, FilterChain chain ) throws IOException, ServletException;

	/**
	* Called by the web container to indicate to a filter that it is being taken out of service. This 
	* method is only called once all threads within the filter's doFilter method have exited or after
	* a timeout period has passed. After the web container calls this method, it will not call the
	* doFilter method again on this instance of the filter. <br><br>
	* 
     	* This method gives the filter an opportunity to clean up any resources that are being held (for
	* example, memory, file handles, threads) and make sure that any persistent state is synchronized
	* with the filter's current state in memory.
	*/

	public void destroy();


}

/*
 * Copyright 2002-2012 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.context;

import javax.servlet.ServletContext;

import org.springframework.beans.factory.Aware;

/**
 * Interface to be implemented by any object that wishes to be notified of the
 * {@link ServletContext} (typically determined by the {@link WebApplicationContext})
 * that it runs in.
 *
 * @author Juergen Hoeller
 * @author Chris Beams
 * @since 12.03.2004
 * @see ServletConfigAware
 */
public interface ServletContextAware extends Aware {

	/**
	 * Set the {@link ServletContext} that this object runs in.
	 * <p>Invoked after population of normal bean properties but before an init
	 * callback like InitializingBean's {@code afterPropertiesSet} or a
	 * custom init-method. Invoked after ApplicationContextAware's
	 * {@code setApplicationContext}.
	 * @param servletContext ServletContext object to be used by this object
	 * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
	 * @see org.springframework.context.ApplicationContextAware#setApplicationContext
	 */
	void setServletContext(ServletContext servletContext);

}