src/main/java/com/gerritforge/gerrit/modules/virtualhost/VirtualHostFilter.java

// Copyright (C) 2017 GerritForge Ltd.
//
// 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.

package com.gerritforge.gerrit.modules.virtualhost;

import java.io.IOException;
import java.util.Optional;

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.HttpServletRequest;

import com.google.common.annotations.VisibleForTesting;

public class VirtualHostFilter implements Filter {
  static final String FORWARDED_HOST_HEADER = "X-FORWARDED-HOST";

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {}

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    CurrentServerName.set(getServerNameFromRequest((HttpServletRequest) request));

    chain.doFilter(request, response);
  }

  @Override
  public void destroy() {}

  @VisibleForTesting
  static String getServerNameFromRequest(HttpServletRequest httpRequest) {
    return Optional.ofNullable(httpRequest.getHeader(FORWARDED_HOST_HEADER))
        .orElseGet(httpRequest::getServerName);
  }
}