text: /*
   * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  package java.beans;
  
  import com.sun.beans.finder.PersistenceDelegateFinder;
  
  import java.util.HashMap;
  import java.util.IdentityHashMap;
  import java.util.Map;
  
  /**
   * An {@code Encoder} is a class which can be used to create
   * files or streams that encode the state of a collection of
   * JavaBeans in terms of their public APIs. The {@code Encoder},
   * in conjunction with its persistence delegates, is responsible for
   * breaking the object graph down into a series of {@code Statement}s
   * and {@code Expression}s which can be used to create it.
   * A subclass typically provides a syntax for these expressions
   * using some human readable form - like Java source code or XML.
   *
   * @since 1.4
   *
   * @author Philip Milne
   */
  
  public class Encoder {
      private final PersistenceDelegateFinder finder = new PersistenceDelegateFinder();
      private Map<Object, Expression> bindings = new IdentityHashMap<>();
      private ExceptionListener exceptionListener;
      boolean executeStatements = true;
      private Map<Object, Object> attributes;
  
      /**
       * Write the specified object to the output stream.
       * The serialized form will denote a series of
       * expressions, the combined effect of which will create
       * an equivalent object when the input stream is read.
       * By default, the object is assumed to be a <em>JavaBean</em>
       * with a nullary constructor, whose state is defined by
       * the matching pairs of "setter" and "getter" methods
       * returned by the Introspector.
       *
       * @param o The object to be written to the stream.
       *
       * @see XMLDecoder#readObject
       */
      protected void writeObject(Object o) {
          if (o == this) {
              return;
          }
          PersistenceDelegate info = getPersistenceDelegate(o == null ? null : o.getClass());
          info.writeObject(o, this);
      }
  
      /**
       * Sets the exception handler for this stream to {@code exceptionListener}.
       * The exception handler is notified when this stream catches recoverable
       * exceptions.
       *
       * @param exceptionListener The exception handler for this stream;
       *       if {@code null} the default exception listener will be used.
       *
       * @see #getExceptionListener
       */
      public void setExceptionListener(ExceptionListener exceptionListener) {
          this.exceptionListener = exceptionListener;
      }
  
      /**
       * Gets the exception handler for this stream.
       *
       * @return The exception handler for this stream;
       *    Will return the default exception listener if this has not explicitly been set.
       *
       * @see #setExceptionListener
       */
      public ExceptionListener getExceptionListener() {
          return (exceptionListener != null) ? exceptionListener : Statement.defaultExceptionListener;
      }
  
      Object getValue(Expression exp) {
          try {
              return (exp == null) ? null : exp.getValue();
          }
          catch (Exception e) {
              getExceptionListener().exceptionThrown(e);
              throw new RuntimeException("failed to evaluate: " + exp.toString());
          }
      }
  
      /**
       * Returns the persistence delegate for the given type.
       * The persistence delegate is calculated by applying
       * the following rules in order:
       * <ol>
       * <li>
       * If a persistence delegate is associated with the given type
       * by using the {@link #setPersistenceDelegate} method
       * it is returned.
       * <li>
       * A persistence delegate is then looked up by the name
       * composed of the fully qualified name of the given type
       * and the "PersistenceDelegate" postfix.
       * For example, a persistence delegate for the {@code Bean} class
       * should be named {@code BeanPersistenceDelegate}
       * and located in the same package.
       * <pre>
       * public class Bean { ... }
       * public class BeanPersistenceDelegate { ... }</pre>
       * The instance of the {@code BeanPersistenceDelegate} class
       * is returned for the {@code Bean} class.
       * <li>
       * If the type is {@code null},
       * a shared internal persistence delegate is returned
       * that encodes {@code null} value.
       * <li>
       * If the type is an {@code enum} declaration,
       * a shared internal persistence delegate is returned
       * that encodes constants of this enumeration
       * by their names.
       * <li>
       * If the type is a primitive type or the corresponding wrapper,
       * a shared internal persistence delegate is returned
       * that encodes values of the given type.
       * <li>
       * If the type is an array,
       * a shared internal persistence delegate is returned
       * that encodes an array of the appropriate type and length,
       * and each of its elements as if they are properties.
       * <li>
       * If the type is a proxy,
       * a shared internal persistence delegate is returned
       * that encodes a proxy instance by using
       * the {@link java.lang.reflect.Proxy#newProxyInstance} method.
       * <li>
       * If the {@link BeanInfo} for this type has a {@link BeanDescriptor}
       * which defined a "persistenceDelegate" attribute,
       * the value of this named attribute is returned.
       * <li>
       * In all other cases the default persistence delegate is returned.
       * The default persistence delegate assumes the type is a <em>JavaBean</em>,
       * implying that it has a default constructor and that its state
       * may be characterized by the matching pairs of "setter" and "getter"
       * methods returned by the {@link Introspector} class.
       * The default constructor is the constructor with the greatest number
       * of parameters that has the {@link ConstructorProperties} annotation.
       * If none of the constructors has the {@code ConstructorProperties} annotation,
       * then the nullary constructor (constructor with no parameters) will be used.
       * For example, in the following code fragment, the nullary constructor
       * for the {@code Foo} class will be used,
       * while the two-parameter constructor
       * for the {@code Bar} class will be used.
       * <pre>
       * public class Foo {
       *     public Foo() { ... }
       *     public Foo(int x) { ... }
       * }
       * public class Bar {
       *     public Bar() { ... }
       *     &#64;ConstructorProperties({"x"})
       *     public Bar(int x) { ... }
       *     &#64;ConstructorProperties({"x", "y"})
       *     public Bar(int x, int y) { ... }
       * }</pre>
       * </ol>
       *
       * @param type  the class of the objects
       * @return the persistence delegate for the given type
       *
       * @see #setPersistenceDelegate
       * @see java.beans.Introspector#getBeanInfo
       * @see java.beans.BeanInfo#getBeanDescriptor
       */
      public PersistenceDelegate getPersistenceDelegate(Class<?> type) {
          PersistenceDelegate pd = this.finder.find(type);
          if (pd == null) {
              pd = MetaData.getPersistenceDelegate(type);
              if (pd != null) {
                  this.finder.register(type, pd);
              }
          }
          return pd;
      }
  
      /**
       * Associates the specified persistence delegate with the given type.
       *
       * @param type  the class of objects that the specified persistence delegate applies to
       * @param delegate  the persistence delegate for instances of the given type
       *
       * @see #getPersistenceDelegate
       * @see java.beans.Introspector#getBeanInfo
       * @see java.beans.BeanInfo#getBeanDescriptor
       */
      public void setPersistenceDelegate(Class<?> type, PersistenceDelegate delegate) {
          this.finder.register(type, delegate);
      }
  
      /**
       * Removes the entry for this instance, returning the old entry.
       *
       * @param oldInstance The entry that should be removed.
       * @return The entry that was removed.
       *
       * @see #get
       */
      public Object remove(Object oldInstance) {
          Expression exp = bindings.remove(oldInstance);
          return getValue(exp);
      }
  
      /**
       * Returns a tentative value for {@code oldInstance} in
       * the environment created by this stream. A persistence
       * delegate can use its {@code mutatesTo} method to
       * determine whether this value may be initialized to
       * form the equivalent object at the output or whether
       * a new object must be instantiated afresh. If the
       * stream has not yet seen this value, null is returned.
       *
       * @param  oldInstance The instance to be looked up.
       * @return The object, null if the object has not been seen before.
       */
      public Object get(Object oldInstance) {
          if (oldInstance == null || oldInstance == this ||
              oldInstance.getClass() == String.class) {
              return oldInstance;
          }
          Expression exp = bindings.get(oldInstance);
          return getValue(exp);
      }
  
      private Object writeObject1(Object oldInstance) {
          Object o = get(oldInstance);
          if (o == null) {
              writeObject(oldInstance);
              o = get(oldInstance);
          }
          return o;
      }
  
      private Statement cloneStatement(Statement oldExp) {
          Object oldTarget = oldExp.getTarget();
          Object newTarget = writeObject1(oldTarget);
  
          Object[] oldArgs = oldExp.getArguments();
          Object[] newArgs = new Object[oldArgs.length];
          for (int i = 0; i < oldArgs.length; i++) {
              newArgs[i] = writeObject1(oldArgs[i]);
          }
          Statement newExp = Statement.class.equals(oldExp.getClass())
                  ? new Statement(newTarget, oldExp.getMethodName(), newArgs)
                  : new Expression(newTarget, oldExp.getMethodName(), newArgs);
          newExp.loader = oldExp.loader;
          return newExp;
      }
  
      /**
       * Writes statement {@code oldStm} to the stream.
       * The {@code oldStm} should be written entirely
       * in terms of the callers environment, i.e. the
       * target and all arguments should be part of the
       * object graph being written. These expressions
       * represent a series of "what happened" expressions
       * which tell the output stream how to produce an
       * object graph like the original.
       * <p>
       * The implementation of this method will produce
       * a second expression to represent the same expression in
       * an environment that will exist when the stream is read.
       * This is achieved simply by calling {@code writeObject}
       * on the target and all the arguments and building a new
       * expression with the results.
       *
       * @param oldStm The expression to be written to the stream.
       */
      public void writeStatement(Statement oldStm) {
          // System.out.println("writeStatement: " + oldExp);
          Statement newStm = cloneStatement(oldStm);
          if (oldStm.getTarget() != this && executeStatements) {
              try {
                  newStm.execute();
              } catch (Exception e) {
                  getExceptionListener().exceptionThrown(new Exception("Encoder: discarding statement "
                                                                       + newStm, e));
              }
          }
      }
  
      /**
       * The implementation first checks to see if an
       * expression with this value has already been written.
       * If not, the expression is cloned, using
       * the same procedure as {@code writeStatement},
       * and the value of this expression is reconciled
       * with the value of the cloned expression
       * by calling {@code writeObject}.
       *
       * @param oldExp The expression to be written to the stream.
       */
      public void writeExpression(Expression oldExp) {
          // System.out.println("Encoder::writeExpression: " + oldExp);
          Object oldValue = getValue(oldExp);
          if (get(oldValue) != null) {
              return;
          }
          bindings.put(oldValue, (Expression)cloneStatement(oldExp));
          writeObject(oldValue);
      }
  
      void clear() {
          bindings.clear();
      }
  
      // Package private method for setting an attributes table for the encoder
      void setAttribute(Object key, Object value) {
          if (attributes == null) {
              attributes = new HashMap<>();
          }
          attributes.put(key, value);
      }
  
      Object getAttribute(Object key) {
          if (attributes == null) {
              return null;
          }
          return attributes.get(key);
      }
  }
  