org.apache.shiro.web.servlet.AbstractFilter Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.shiro.web.servlet;
import org.apache.shiro.util.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
/**
* Base abstract Filter simplifying Filter initialization and {@link #getInitParam(String) access} to init parameters.
* Subclass initialization logic should be performed by overriding the {@link #onFilterConfigSet()} template method.
* FilterChain execution logic (the
* {@link #doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)} method
* is left to subclasses.
*
* @since 1.0
*/
public abstract class AbstractFilter extends ServletContextSupport implements Filter {
private static transient final Logger log = LoggerFactory.getLogger(AbstractFilter.class);
/**
* FilterConfig provided by the Servlet container at start-up.
*/
protected FilterConfig filterConfig;
/**
* Returns the servlet container specified {@code FilterConfig} instance provided at
* {@link #init(javax.servlet.FilterConfig) startup}.
*
* @return the servlet container specified {@code FilterConfig} instance provided at start-up.
*/
public FilterConfig getFilterConfig() {
return filterConfig;
}
/**
* Sets the FilterConfig and the {@code ServletContext} as attributes of this class for use by
* subclasses. That is:
*
* this.filterConfig = filterConfig;
* setServletContext(filterConfig.getServletContext());
*
* @param filterConfig the FilterConfig instance provided by the Servlet container at start-up.
*/
public void setFilterConfig(FilterConfig filterConfig) {
this.filterConfig = filterConfig;
setServletContext(filterConfig.getServletContext());
}
/**
* Returns the value for the named {@code init-param}, or {@code null} if there was no {@code init-param}
* specified by that name.
*
* @param paramName the name of the {@code init-param}
* @return the value for the named {@code init-param}, or {@code null} if there was no {@code init-param}
* specified by that name.
*/
protected String getInitParam(String paramName) {
FilterConfig config = getFilterConfig();
if (config != null) {
return StringUtils.clean(config.getInitParameter(paramName));
}
return null;
}
/**
* Sets the filter's {@link #setFilterConfig filterConfig} and then immediately calls
* {@link #onFilterConfigSet() onFilterConfigSet()} to trigger any processing a subclass might wish to perform.
*
* @param filterConfig the servlet container supplied FilterConfig instance.
* @throws javax.servlet.ServletException if {@link #onFilterConfigSet() onFilterConfigSet()} throws an Exception.
*/
public final void init(FilterConfig filterConfig) throws ServletException {
setFilterConfig(filterConfig);
try {
onFilterConfigSet();
} catch (Exception e) {
if (e instanceof ServletException) {
throw (ServletException) e;
} else {
if (log.isErrorEnabled()) {
log.error("Unable to start Filter: [" + e.getMessage() + "].", e);
}
throw new ServletException(e);
}
}
}
/**
* Template method to be overridden by subclasses to perform initialization logic at start-up. The
* {@code ServletContext} and {@code FilterConfig} will be accessible
* (and non-{@code null}) at the time this method is invoked via the
* {@link #getServletContext() getServletContext()} and {@link #getFilterConfig() getFilterConfig()}
* methods respectively.
*
* {@code init-param} values may be conveniently obtained via the {@link #getInitParam(String)} method.
*
* @throws Exception if the subclass has an error upon initialization.
*/
protected void onFilterConfigSet() throws Exception {
}
/**
* Default no-op implementation that can be overridden by subclasses for custom cleanup behavior.
*/
public void destroy() {
}
}