SessionInitializerFilter.java

/*
 * 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.catalina.filters;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

/**
 * A {@link javax.servlet.Filter} that initializes the {@link HttpSession} for the {@link HttpServletRequest} by calling
 * its getSession() method.
 * <p>
 * This is required for some operations with WebSocket requests, where it is too late to initialize the HttpSession
 * object, and the current Java WebSocket specification does not provide a way to do so.
 */
public class SessionInitializerFilter implements Filter {

    /**
     * Calls {@link HttpServletRequest}'s getSession() to initialize the HttpSession and continues processing the 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
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {

        ((HttpServletRequest) request).getSession();

        chain.doFilter(request, response);
    }

}