https://projects.eclipse.org/projects/ee4j.servlet: Provides, via submodules, a base configuration for JBoss project builds, as well as a derived configuration supporting multi-release JARs (JBoss by Red Hat)
  • Ed Burns
  • Shing Wai Chan 
/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates and others.
 * All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.servlet;

import java.util.Enumeration;
import java.util.ResourceBundle;


 Defines a generic, protocol-independent filter. To write an HTTP filter for use on the Web, extend HttpFilter instead. 



GenericFilter implements the Filter and FilterConfig interfaces.
GenericFilter may be directly extended by a filter, although it's more common to extend a
protocol-specific subclass such as HttpFilter.


GenericFilter makes writing filters easier. It provides simple versions of the lifecycle methods
init and destroy and of the methods in the FilterConfig interface.


To write a generic filter, you need only override the abstract doFilter method.

Author:Various
Since:Servlet 4.0
/**
 *
 * <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 long serialVersionUID = 4060116231031076581L;

    private static final String LSTRING_FILE = "javax.servlet.LocalStrings";
    private static final ResourceBundle lStrings = ResourceBundle.getBundle(LSTRING_FILE);

    private transient FilterConfig config;

    

Does nothing. All of the filter initialization is done by one of the init methods.



Since:Servlet 4.0
/**
     *
     * <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() {
    }

    

Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist. See FilterConfig.getInitParameter. 



This method is supplied for convenience. It gets the value of the named parameter from the servlet's
ServletConfig object.

Params:
  • name – a String specifying the name of the initialization parameter
Returns:String a String containing the value of the initialization parameter
Since:Servlet 4.0
/**
     * <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);
    }

    

Returns the names of the filter's initialization parameters as an Enumeration of String
objects, or an empty Enumeration if the filter has no initialization parameters. See FilterConfig.getInitParameterNames. 



This method is supplied for convenience. It gets the parameter names from the filter's FilterConfig
object.

Returns:Enumeration an enumeration of String objects containing the names of the filter's
        initialization parameters
Since:Servlet 4.0
/**
     * <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();
    }

    
 Returns this servlet's ServletConfig object. 


Returns:FilterConfig the FilterConfig object that initialized this filter
Since:Servlet 4.0
/**
     * <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;
    }

    
 Returns a reference to the ServletContext in which this filter is running. See FilterConfig.getServletContext. 



This method is supplied for convenience. It gets the context from the filter's FilterConfig object.

Returns:ServletContext the ServletContext object passed to this filter by the init
        method
Since:Servlet 4.0
/**
     * <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();
    }

    
 Called by the servlet container to indicate to a filter that it is being placed into service. See Filter.init. 


 This implementation stores the FilterConfig object it receives from the servlet container for later use. When overriding this form of the method, call super.init(config).

Params:
  • config – the FilterConfig object that contains configuration information for this filter
Throws:
  • ServletException – if an exception occurs that interrupts the servlet's normal operation
See Also:
Since:Servlet 4.0
/**
     * <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();
    }

    

A convenience method which can be overridden so that there's no need to call super.init(config).



 Instead of overriding init(FilterConfig), simply override this method and it will be called by GenericFilter.init(FilterConfig config). The FilterConfig object can still be retrieved via getFilterConfig. 
Throws:
  • ServletException – if an exception occurs that interrupts the servlet's normal operation
Since:Servlet 4.0
/**
     * <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 {

    }

    
 Returns the name of this filter instance. See FilterConfig.getFilterName. 


Returns:the name of this filter instance
Since:Servlet 4.0
/**
     * <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();
    }
}