content: /*
   * 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.activemq.artemis.jndi;
  
  import javax.naming.NameNotFoundException;
  import javax.naming.NamingException;
  
  public abstract class LazyCreateContext extends ReadOnlyContext {
  
     @Override
     public Object lookup(String name) throws NamingException {
        /*
         * The lookup and the internalBind should be performed atomically to avoid
         * race conditions between multiple threads where the lookup fails for both
         * threads initially then the internalBind fails for the second thread.
         */
        synchronized (this) {
           try {
              return super.lookup(name);
           } catch (NameNotFoundException e) {
              Object answer = createEntry(name);
              if (answer == null) {
                 throw e;
              }
              internalBind(name, answer);
              return answer;
           }
        }
     }
  
     protected abstract Object createEntry(String name);
  }
  