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/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 1997-2017 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://oss.oracle.com/licenses/CDDL+GPL-1.1
* or LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package javax.servlet;
import java.io.IOException;
import java.util.Enumeration;
import java.util.ResourceBundle;
/**
*
* <p>Defines a generic, protocol-independent
* filter. To write an HTTP filter for use on the
* Web, extend {@link javax.servlet.http.HttpFilter} instead.</p>
*
* <p><code>GenericFilter</code> implements the <code>Filter</code>
* and <code>FilterConfig</code> interfaces. <code>GenericFilter</code>
* may be directly extended by a filter, although it's more common to extend
* a protocol-specific subclass such as <code>HttpFilter</code>.
*
* <p><code>GenericFilter</code> makes writing filters
* easier. It provides simple versions of the lifecycle methods
* <code>init</code> and <code>destroy</code> and of the methods
* in the <code>FilterConfig</code> interface.
*
* <p>To write a generic filter, you need only
* override the abstract <code>doFilter</code> method.
*
* @author Various
*
* @since Servlet 4.0
*/
public abstract class GenericFilter
implements Filter, FilterConfig, java.io.Serializable
{
private static final String LSTRING_FILE = "javax.servlet.LocalStrings";
private static final ResourceBundle lStrings =
ResourceBundle.getBundle(LSTRING_FILE);
private transient FilterConfig config;
/**
*
* <p>Does nothing. All of the filter initialization
* is done by one of the <code>init</code> methods.</p>
*
* @since Servlet 4.0
*/
public GenericFilter() { }
/**
* <p>Returns a <code>String</code> containing the value of the named
* initialization parameter, or <code>null</code> if the parameter does
* not exist. See {@link FilterConfig#getInitParameter}.</p>
*
* <p>This method is supplied for convenience. It gets the
* value of the named parameter from the servlet's
* <code>ServletConfig</code> object.
*
* @param name a <code>String</code> specifying the name
* of the initialization parameter
*
* @return String a <code>String</code> containing the value
* of the initialization parameter
*
* @since Servlet 4.0
*
*/
@Override
public String getInitParameter(String name) {
FilterConfig fc = getFilterConfig();
if (fc == null) {
throw new IllegalStateException(
lStrings.getString("err.filter_config_not_initialized"));
}
return fc.getInitParameter(name);
}
/**
* <p>Returns the names of the filter's initialization parameters
* as an <code>Enumeration</code> of <code>String</code> objects,
* or an empty <code>Enumeration</code> if the filter has no
* initialization parameters. See {@link
* FilterConfig#getInitParameterNames}.</p>
*
* <p>This method is supplied for convenience. It gets the
* parameter names from the filter's <code>FilterConfig</code> object.
*
* @return Enumeration an enumeration of <code>String</code>
* objects containing the names of
* the filter's initialization parameters
*
* @since Servlet 4.0
*/
@Override
public Enumeration<String> getInitParameterNames() {
FilterConfig fc = getFilterConfig();
if (fc == null) {
throw new IllegalStateException(
lStrings.getString("err.filter_config_not_initialized"));
}
return fc.getInitParameterNames();
}
/**
* <p>Returns this servlet's {@link ServletConfig} object.</p>
*
* @return FilterConfig the <code>FilterConfig</code> object
* that initialized this filter
*
* @since Servlet 4.0
*/
public FilterConfig getFilterConfig() {
return config;
}
/**
* <p>Returns a reference to the {@link ServletContext} in which this filter
* is running. See {@link FilterConfig#getServletContext}.</p>
*
* <p>This method is supplied for convenience. It gets the
* context from the filter's <code>FilterConfig</code> object.
*
* @return ServletContext the <code>ServletContext</code> object
* passed to this filter by the <code>init</code>
* method
*
* @since Servlet 4.0
*/
@Override
public ServletContext getServletContext() {
FilterConfig sc = getFilterConfig();
if (sc == null) {
throw new IllegalStateException(
lStrings.getString("err.filter_config_not_initialized"));
}
return sc.getServletContext();
}
/**
* <p>Called by the servlet container to indicate to a filter that
* it is being placed into service. See {@link Filter#init}.</p>
*
* <p>This implementation stores the {@link FilterConfig}
* object it receives from the servlet container for later use.
* When overriding this form of the method, call
* <code>super.init(config)</code>.
*
* @param config the <code>FilterConfig</code> object
* that contains configuration
* information for this filter
*
* @exception ServletException if an exception occurs that
* interrupts the servlet's normal
* operation
*
* @see UnavailableException
*
* @since Servlet 4.0
*/
@Override
public void init(FilterConfig config) throws ServletException {
this.config = config;
this.init();
}
/**
* <p>A convenience method which can be overridden so that there's no need
* to call <code>super.init(config)</code>.</p>
*
* <p>Instead of overriding {@link #init(FilterConfig)}, simply override
* this method and it will be called by
* <code>GenericFilter.init(FilterConfig config)</code>.
* The <code>FilterConfig</code> object can still be retrieved via {@link
* #getFilterConfig}.
*
* @exception ServletException if an exception occurs that
* interrupts the servlet's
* normal operation
*
* @since Servlet 4.0
*/
public void init() throws ServletException {
}
/**
* <p>Returns the name of this filter instance.
* See {@link FilterConfig#getFilterName}.</p>
*
* @return the name of this filter instance
*
* @since Servlet 4.0
*/
@Override
public String getFilterName() {
FilterConfig sc = getFilterConfig();
if (sc == null) {
throw new IllegalStateException(
lStrings.getString("err.servlet_config_not_initialized"));
}
return sc.getFilterName();
}
}