/*   * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.   * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.   */   package java.io;   /**   * Context during upcalls from object stream to class-defined   * readObject/writeObject methods.   * Holds object currently being deserialized and descriptor for current class.   *   * This context keeps track of the thread it was constructed on, and allows   * only a single call of defaultReadObject, readFields, defaultWriteObject   * or writeFields which must be invoked on the same thread before the class's   * readObject/writeObject method has returned.   * If not set to the current thread, the getObj method throws NotActiveException.   */  final class SerialCallbackContext {      private final Object obj;      private final ObjectStreamClass desc;      /**       * Thread this context is in use by.       * As this only works in one thread, we do not need to worry about thread-safety.       */      private Thread thread;       public SerialCallbackContext(Object obj, ObjectStreamClass desc) {          this.obj = obj;          this.desc = desc;          this.thread = Thread.currentThread();      }       public Object getObj() throws NotActiveException {          checkAndSetUsed();          return obj;      }       public ObjectStreamClass getDesc() {          return desc;      }       private void checkAndSetUsed() throws NotActiveException {          if (thread != Thread.currentThread()) {               throw new NotActiveException(                "not in readObject invocation or fields already read");          }          thread = null;      }       public void setUsed() {          thread = null;      }  }