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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 javax.servlet.http;
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.GenericFilter;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
/**
* Provides a base class that implements the Filter interface and ensures that the Request and Response are of type
* HttpServletRequest and HttpServletResponse respectively.
*/
public abstract class HttpFilter extends GenericFilter {
private static final long serialVersionUID = 1L;
/**
* {@inheritDoc} This implementation tests the request and response to see if they are instances of
* {@link HttpServletRequest} and {@link HttpServletResponse} respectively. If they are then they are passed to
* {@link #doFilter(HttpServletRequest, HttpServletResponse, FilterChain)}. If not, a {@link ServletException} is
* thrown.
*
* @throws ServletException If either the request or response are not of the expected types or any other error
* occurs
*/
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
if (!(request instanceof HttpServletRequest)) {
throw new ServletException(request + " not HttpServletRequest");
}
if (!(response instanceof HttpServletResponse)) {
throw new ServletException(response + " not HttpServletResponse");
}
doFilter((HttpServletRequest) request, (HttpServletResponse) response, chain);
}
/**
* 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. This default
* implementation simply calls the next filter in the filter chain.
*
* @param request The request to process
* @param response The response associated with the request
* @param chain Provides access to the next filter in the chain for this filter to pass the request and response
* to for further processing
*
* @throws IOException if an I/O error occurs during this filter's processing of the request
* @throws ServletException if the processing fails for any other reason
*/
protected void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
throws IOException, ServletException {
chain.doFilter(request, response);
}
}
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