Example of a readOldVersion Method
This method is generated virtually the same as readVersion <EXTERBALIZATION_VERSION_UID> to support backward compatibility. To support backward compatibility for multiple releases, the method should include a conditional block for each old version that is being supported. Each condition should check for the version UID that was used in that version of the class, and the block that reads the fields should be the same set of read calls that the were used for that version. The generated OLD_FORMAT_VERSION_UID constant is only valid for R4 instances of the class. Fields that no longer exist can be read and discarded (not assigned). Fields that didn't exist for the version can be initialized in the manner necessary to put the object into a valid state.
private boolean readOldVersion( ObjectInput input,
long readSerialVersionUID, boolean passThrough, boolean superDone )
throws IOException, ClassNotFoundException {
//##begin readOldVersion%readOldVersion.body preserve=no
boolean success = true;
// handle previous version
if ( readSerialVersionUID == OLD_FORMAT_VERSION_UID ) {
a1 = (String)input.readObject();
a2 = (Date)input.readObject();
a3 = (Xyz)input.readObject();
list = (Vector)input.readObject();
String size_string_value = (String)input.readObject();
try { size = (MySize)wt.fc.EnumeratedType.toEnumeratedType(
size_string_value ); }
// in case it was old format
catch( wt.util.WTInvalidParameterException e ) {
size = MySize.toMySize( size_string_value );
}
theOneMoreReference = (ObjectReference)input.readObject();
timeline = (Timeline)input.readObject();
work = (MyAddress)input.readObject();
}
else if ( !superDone ) {
success = super.readVersion( this, input,
readSerialVersionUID, false, false ); // reformatted stream-
if ( success && !passThrough && // forced pass through to
skip me
// I have been inserted into hierarchy
readSerialVersionUID != super.EXTERNALIZATION_VERSION_UID )
// try mine again
readVersion( this, input, input.readLong(), false, true );
}
else
throw new java.io.InvalidClassException( CLASSNAME,
"Local class not compatible:"
+ " stream classdesc externalizationVersionUID=
" + readSerialVersionUID
+ " local class externalizationVersionUID=
" + EXTERNALIZATION_VERSION_UID );
return success;
//##end readOldVersion%readOldVersion.body
}