code: /**
   * This file is part of Eclipse Steady.
   *
   * Licensed 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.
   *
   * SPDX-License-Identifier: Apache-2.0
   * SPDX-FileCopyrightText: Copyright (c) 2018-2020 SAP SE or an SAP affiliate company and Eclipse Steady contributors
   */
  package org.eclipse.steady.cia.util;
  
  import java.io.IOException;
  
  import javax.servlet.Filter;
  import javax.servlet.FilterChain;
  import javax.servlet.FilterConfig;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletResponse;
  
  import org.springframework.stereotype.Component;
  
  // Component duplicated in
  // rest-backend/src/main/java/com/sap/psr/vulas/backend/util/CacheFilter.java
  
  /**
   * <p>CacheFilter class.</p>
   */
  @Component
  public class CacheFilter implements Filter {
  
    /** {@inheritDoc} */
    @Override
    public void destroy() {
      // Nothing
    }
  
    /**
     * {@inheritDoc}
     *
     * Appends to the response a X-Accel-Expires header equal to two hours if cache=true is present in the querystring of the request
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
        throws IOException, ServletException {
      String cache = request.getParameter("cache");
      if (cache != null && cache.equals("true")) {
        // Instructs Nginx to cache the response for 2 hours
        HttpServletResponse httpServletResponse = (HttpServletResponse) response;
        httpServletResponse.setHeader("X-Accel-Expires", "7200");
      }
      chain.doFilter(request, response);
    }
  
    /** {@inheritDoc} */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
      // Nothing
    }
  }
  