PropertyEditor interface, a bean developer can
provide an editor for this special type.
To minimize the resources used by a bean, the classes used by bean editors are loaded only when the bean is being edited. They are not needed while the bean is running in an application and therefore not loaded. This information is kept in what's called a bean-info (see {@link java.beans.BeanInfo}).
Unless explicitly stated, null values or empty Strings are not valid parameters for the methods in this package. You may expect to see exceptions if these parameters are used.
java.beans package provides support for
long-term persistence -- reading and
writing a bean as a textual representation of its property values.
The property values are treated as beans,
and are recursively read or written to capture
their publicly available state.
This approach is suitable for long-term storage
because it relies only on public API,
rather than the likely-to-change private implementation.
Note: The persistence scheme cannot automatically instantiate custom inner classes, such as you might use for event handlers. By using the {@link java.beans.EventHandler} class instead of inner classes for custom event handlers, you can avoid this problem.
You read and write beans in XML format using the {@link java.beans.XMLDecoder} and {@link java.beans.XMLEncoder} classes, respectively. One notable feature of the persistence scheme is that reading in a bean requires no special knowledge of the bean.
Writing out a bean, on the other hand,
sometimes requires special knowledge of the bean's type.
If the bean's state can be
expressed using only the no-argument constructor and
public getter and setter methods for properties,
no special knowledge is required.
Otherwise, the bean requires a custom persistence delegate --
an object that is in charge of writing out beans of a particular type.
All classes provided in the JDK that descend
from java.awt.Component,
as well as all their properties,
automatically have persistence delegates.
If you need (or choose) to provide a persistence delegate for a bean,
you can do so either by using a
{@link java.beans.DefaultPersistenceDelegate}
instance
or by creating your own subclass of PersistenceDelegate.
If the only reason a bean needs a persistence delegate
is because you want to invoke the bean's constructor with
property values as arguments,
you can create the bean's persistence delegate
with the one-argument
DefaultPersistenceDelegate
constructor.
Otherwise,
you need to implement your own persistence delegate,
for which you're likely to need the following classes:
Statements and Expressions
are necessary to create the bean
and restore its state.
Statement
used for methods that return a value.
Once you create a persistence delegate,
you register it using the
setPersistenceDelegate method of
XMLEncoder.