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.kafka.common.internals;
  
  import java.lang.reflect.Method;
  import java.security.PrivilegedAction;
  import java.util.concurrent.Callable;
  import java.util.concurrent.CompletionException;
  
  import javax.security.auth.Subject;
  
  /**
   * This class implements reflective access to the methods of Subject added to replace deprecated methods.
   * <p>Instantiating this class may fail if any of the required classes or methods are not found.
   * Method invocations for this class may fail with {@link UnsupportedOperationException} if all methods are found,
   * but the operation is not permitted to be invoked.
   * <p>This class is expected to be instantiable in JRE >= 18. At the time of writing, these methods do not have
   * a sunset date, and are expected to be available past the removal of the SecurityManager.
   */
  @SuppressWarnings("unchecked")
  class ModernStrategy implements SecurityManagerCompatibility {
  
      private final Method current;
      private final Method callAs;
  
      // Visible for testing
      ModernStrategy(ReflectiveStrategy.Loader loader) throws NoSuchMethodException, ClassNotFoundException {
          Class<?> subject = loader.loadClass(Subject.class.getName());
          current = subject.getDeclaredMethod("current");
          // Note that the Subject class isn't deprecated or removed, so reference it as an argument type.
          // This allows for mocking out the method implementation while still accepting Subject instances as arguments.
          callAs = subject.getDeclaredMethod("callAs", Subject.class, Callable.class);
      }
  
      @Override
      public <T> T doPrivileged(PrivilegedAction<T> action) {
          // This is intentionally a pass-through
          return action.run();
      }
  
      @Override
      public Subject current() {
          return (Subject) ReflectiveStrategy.invoke(current, null);
      }
  
      @Override
      public <T> T callAs(Subject subject, Callable<T> action) throws CompletionException {
          return (T) ReflectiveStrategy.invokeChecked(callAs, CompletionException.class, null, subject, action);
      }
  }
  