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## java.beans
Class Encoder

    java.lang.Object
      java.beans.Encoder

Direct Known Subclasses:
  XMLEncoder

    public class Encoder

extends Object

An `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 `Encoder`, in conjunction with its persistence delegates, is responsible for breaking the object graph down into a series of `Statements`s and `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

Constructor Summary
`Encoder()`

Method Summary
`Object` | `get(Object oldInstance)` Returns a tentative value for `oldInstance` in the environment created by this stream.
`ExceptionListener` | `getExceptionListener()` Gets the exception handler for this stream.
`PersistenceDelegate` | `getPersistenceDelegate(Class<?> type)` Returns the persistence delegate for the given type.
`Object` | `remove(Object oldInstance)` Removes the entry for this instance, returning the old entry.
`void` | `setExceptionListener(ExceptionListener exceptionListener)` Sets the exception handler for this stream to `exceptionListener`.
`void` | `setPersistenceDelegate(Class<?> type, PersistenceDelegate persistenceDelegate)` Sets the persistence delegate associated with this `type` to `persistenceDelegate`.
`void` | `writeExpression(Expression oldExp)` The implementation first checks to see if an expression with this value has already been written.
`protected void` | `writeObject(Object o)` Write the specified object to the output stream.
`void` | `writeStatement(Statement oldStm)` Writes statement `oldStm` to the stream.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### Encoder

    public Encoder()

Method Detail

### writeObject

    protected void writeObject(Object o)

  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 JavaBean with a nullary constructor, whose state is defined by the matching pairs of "setter" and "getter" methods returned by the Introspector.

  Parameters:
    `o` - The object to be written to the stream.
  See Also:
    `XMLDecoder.readObject()`

### setExceptionListener

    public void setExceptionListener(ExceptionListener exceptionListener)

  Sets the exception handler for this stream to `exceptionListener`. The exception handler is notified when this stream catches recoverable exceptions.

  Parameters:
    `exceptionListener` - The exception handler for this stream; if `null` the default exception listener will be used.
  See Also:
    `getExceptionListener()`

### getExceptionListener

    public ExceptionListener getExceptionListener()

  Gets the exception handler for this stream.

  Returns:
    The exception handler for this stream; Will return the default exception listener if this has not explicitly been set.
  See Also:
    `setExceptionListener(java.beans.ExceptionListener)`

### getPersistenceDelegate

    public PersistenceDelegate getPersistenceDelegate(Class<?> type)

  Returns the persistence delegate for the given type. The persistence delegate is calculated by applying the following of rules in order:
  - If the type is an array, an internal persistence delegate is returned which will instantiate an array of the appropriate type and length, initializing each of its elements as if they are properties.
  - If the type is a proxy, an internal persistence delegate is returned which will instantiate a new proxy instance using the static "newProxyInstance" method defined in the Proxy class.
  - If the BeanInfo for this type has a `BeanDescriptor` which defined a "persistenceDelegate" property, this value is returned.
  - In all other cases the default persistence delegate is returned. The default persistence delegate assumes the type is a JavaBean, implying that it has a nullary constructor and that its state may be characterized by the matching pairs of "setter" and "getter" methods returned by the Introspector.

  Parameters:
    `type` - The type of the object.
  Returns:
    The persistence delegate for this type of object.
  See Also:
    `setPersistenceDelegate(java.lang.Class, java.beans.PersistenceDelegate)`, `Introspector.getBeanInfo(java.lang.Class)`, `BeanInfo.getBeanDescriptor()`

### setPersistenceDelegate

    public void setPersistenceDelegate(Class<?> type,
                                       PersistenceDelegate persistenceDelegate)

  Sets the persistence delegate associated with this `type` to `persistenceDelegate`.

  Parameters:
    `type` - The class of objects that `persistenceDelegate` applies to.
    `persistenceDelegate` - The persistence delegate for instances of `type`.
  See Also:
    `getPersistenceDelegate(java.lang.Class)`, `Introspector.getBeanInfo(java.lang.Class)`, `BeanInfo.getBeanDescriptor()`

### remove

    public Object remove(Object oldInstance)

  Removes the entry for this instance, returning the old entry.

  Parameters:
    `oldInstance` - The entry that should be removed.
  Returns:
    The entry that was removed.
  See Also:
    `get(java.lang.Object)`

### get

    public Object get(Object oldInstance)

  Returns a tentative value for `oldInstance` in the environment created by this stream. A persistence delegate can use its `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.

  Parameters:
    `oldInstance` - The instance to be looked up.
  Returns:
    The object, null if the object has not been seen before.

### writeStatement

    public void writeStatement(Statement oldStm)

  Writes statement `oldStm` to the stream. The `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.

  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 `writeObject` on the target and all the arguments and building a new expression with the results.

  Parameters:
    `oldStm` - The expression to be written to the stream.

### writeExpression

    public void writeExpression(Expression oldExp)

  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 `writeStatement`, and the value of this expression is reconciled with the value of the cloned expression by calling `writeObject`.

  Parameters:
    `oldExp` - The expression to be written to the stream.

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2004 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.