This default implementation of the initialize method assumes
all state held in objects of this type is exposed via the
matching pairs of "setter" and "getter" methods in the order
they are returned by the Introspector. If a property descriptor
defines a "transient" attribute with a value equal to
Boolean.TRUE the property is ignored by this
default implementation. Note that this use of the word
"transient" is quite independent of the field modifier
that is used by the ObjectOutputStream.
For each non-transient property, an expression is created
in which the nullary "getter" method is applied
to the oldInstance. The value of this
expression is the value of the property in the instance that is
being serialized. If the value of this expression
in the cloned environment mutatesTo the
target value, the new value is initialized to make it
equivalent to the old value. In this case, because
the property value has not changed there is no need to
call the corresponding "setter" method and no statement
is emitted. If not however, the expression for this value
is replaced with another expression (normally a constructor)
and the corresponding "setter" method is called to install
the new property value in the object. This scheme removes
default information from the output produced by streams
using this delegate.
In passing these statements to the output stream, where they
will be executed, side effects are made to the newInstance.
In most cases this allows the problem of properties
whose values depend on each other to actually help the
serialization process by making the number of statements
that need to be written to the output smaller. In general,
the problem of handling interdependent properties is reduced to
that of finding an order for the properties in
a class such that no property value depends on the value of
a subsequent property.
type | the type of the instances | |
oldInstance | The instance to be copied. | |
newInstance | The instance that is to be modified. | |
out | The stream to which any initialization statements should be written. |
java.beans.Introspector.getBeanInfo, java.beans.PropertyDescriptor
This default implementation of the instantiate method returns
an expression containing the predefined method name "new" which denotes a
call to a constructor with the arguments as specified in
the DefaultPersistenceDelegate's constructor.
oldInstance | The instance to be instantiated. | |
out | The code output stream. |
oldInstance.
DefaultPersistenceDelegate(String[])
If the number of arguments in the specified constructor is non-zero and
the class of oldInstance explicitly declares an "equals" method
this method returns the value of oldInstance.equals(newInstance).
Otherwise, this method uses the superclass's definition which returns true if the
classes of the two instances are equal.
oldInstance | The instance to be copied. | |
newInstance | The instance that is to be modified. |
newInstance may be
created by applying a series of mutations to oldInstance.
DefaultPersistenceDelegate(String[])
Diagram: Persistence