jakarta.servlet.http.HttpFilter Maven / Gradle / Ivy
/*
* 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 jakarta.servlet.http;
import java.io.IOException;
import jakarta.servlet.FilterChain;
import jakarta.servlet.GenericFilter;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.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(request + " not HttpServletResponse");
}
doFilter((HttpServletRequest) request, (HttpServletResponse) response, chain);
}
/**
* The doFilter 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.
*
* A typical implementation of this method would follow the following
* pattern:-
* 1. Examine the request
* 2. Optionally wrap the request object with a custom implementation to
* filter content or headers for input filtering
* 3. Optionally wrap the response object with a custom implementation to
* filter content or headers for output filtering
* 4. a) Either invoke the next entity in the chain using
* the FilterChain object (chain.doFilter()),
* 4. b) or not pass on the request/response pair to the
* next entity in the filter chain to block the request processing
* 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);
}
}