exec/java-exec/src/main/java/org/apache/drill/exec/server/rest/header/ResponseHeadersSettingFilter.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.drill.exec.server.rest.header;

import com.typesafe.config.ConfigObject;
import org.apache.drill.common.config.DrillConfig;
import org.apache.drill.exec.ExecConstants;

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 java.io.IOException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

/**
 * Responsible for setting configured {@link ExecConstants#HTTP_JETTY_SERVER_RESPONSE_HEADERS}
 * to {@link HttpServletResponse} object.
 */
public class ResponseHeadersSettingFilter implements Filter {

  private Map<String, String> responseHeaders;

  public static Map<String, String> retrieveResponseHeaders(DrillConfig config) {
    Map<String, String> headers = new HashMap<>();
    if (config.hasPath(ExecConstants.HTTP_JETTY_SERVER_RESPONSE_HEADERS)) {
      ConfigObject headersConf = config.getObject(ExecConstants.HTTP_JETTY_SERVER_RESPONSE_HEADERS);
      for (String header : headersConf.keySet()) {
        Object val = headersConf.get(header).unwrapped();
        headers.put(header, val == null ? null : val.toString());
      }
    }
    return headers;
  }

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    responseHeaders = new HashMap<>();
    Enumeration<String> headers = filterConfig.getInitParameterNames();
    while (headers.hasMoreElements()) {
      String header = headers.nextElement();
      String value = filterConfig.getInitParameter(header);
      responseHeaders.put(header, value);
    }
  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    responseHeaders.forEach(((HttpServletResponse) response)::setHeader);
    chain.doFilter(request, response);
  }

  @Override
  public void destroy() {
    responseHeaders = null;
  }
}