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.security.PrivilegedActionException;
  import java.security.PrivilegedExceptionAction;
  import java.util.concurrent.Callable;
  import java.util.concurrent.CompletionException;
  
  import javax.security.auth.Subject;
  
  /**
   * This class implements reflective access to the deprecated-for-removal methods of AccessController and Subject.
   * <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 >=8 until the removal finally takes place.
   */
  @SuppressWarnings("unchecked")
  class LegacyStrategy implements SecurityManagerCompatibility {
  
      private final Method doPrivileged;
      private final Method getContext;
      private final Method getSubject;
      private final Method doAs;
  
      // Visible for testing
      LegacyStrategy(ReflectiveStrategy.Loader loader) throws ClassNotFoundException, NoSuchMethodException {
          Class<?> accessController = loader.loadClass("java.security.AccessController");
          doPrivileged = accessController.getDeclaredMethod("doPrivileged", PrivilegedAction.class);
          getContext = accessController.getDeclaredMethod("getContext");
          Class<?> accessControlContext = loader.loadClass("java.security.AccessControlContext");
          Class<?> subject = loader.loadClass(Subject.class.getName());
          getSubject = subject.getDeclaredMethod("getSubject", accessControlContext);
          // 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.
          doAs = subject.getDeclaredMethod("doAs", Subject.class, PrivilegedExceptionAction.class);
      }
  
      @Override
      public <T> T doPrivileged(PrivilegedAction<T> action) {
          return (T) ReflectiveStrategy.invoke(doPrivileged, null, action);
      }
  
      /**
       * @return the result of AccessController.getContext(), of type AccessControlContext
       */
      private Object getContext() {
          return ReflectiveStrategy.invoke(getContext, null);
      }
  
      /**
       * @param context The current AccessControlContext
       * @return The result of Subject.getSubject(AccessControlContext)
       */
      private Subject getSubject(Object context) {
          return (Subject) ReflectiveStrategy.invoke(getSubject, null, context);
      }
  
      @Override
      public Subject current() {
          return getSubject(getContext());
      }
  
      /**
       * @return The result of Subject.doAs(Subject, PrivilegedExceptionAction)
       */
      private <T> T doAs(Subject subject, PrivilegedExceptionAction<T> action) throws PrivilegedActionException {
          return (T) ReflectiveStrategy.invokeChecked(doAs, PrivilegedActionException.class, null, subject, action);
      }
  
      @Override
      public <T> T callAs(Subject subject, Callable<T> callable) throws CompletionException {
          try {
              return doAs(subject, callable::call);
          } catch (PrivilegedActionException e) {
              throw new CompletionException(e.getCause());
          }
      }
  }
  