code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC 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.openqa.selenium.grid.distributor;
  
  import static java.net.HttpURLConnection.HTTP_INTERNAL_ERROR;
  import static java.util.Collections.singletonMap;
  
  import java.io.UncheckedIOException;
  import java.util.Map;
  import org.openqa.selenium.SessionNotCreatedException;
  import org.openqa.selenium.grid.data.CreateSessionResponse;
  import org.openqa.selenium.grid.data.SessionRequest;
  import org.openqa.selenium.internal.Either;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.remote.http.Contents;
  import org.openqa.selenium.remote.http.HttpHandler;
  import org.openqa.selenium.remote.http.HttpRequest;
  import org.openqa.selenium.remote.http.HttpResponse;
  
  class CreateSession implements HttpHandler {
  
    private final Distributor distributor;
  
    CreateSession(Distributor distributor) {
      this.distributor = Require.nonNull("Distributor", distributor);
    }
  
    @Override
    public HttpResponse execute(HttpRequest req) throws UncheckedIOException {
      SessionRequest request = Contents.fromJson(req, SessionRequest.class);
  
      Either<SessionNotCreatedException, CreateSessionResponse> result =
          distributor.newSession(request);
  
      HttpResponse res = new HttpResponse();
      Map<String, Object> value;
      if (result.isLeft()) {
        res.setStatus(HTTP_INTERNAL_ERROR);
        value = singletonMap("value", result.left());
      } else {
        value = singletonMap("value", result.right());
      }
  
      res.setContent(Contents.asJson(value));
  
      return res;
    }
  }
  