To deserialise an object, GWT calls the no-argument constructor (which
you haven't specified, but is required) and then modifies the fields to
match what is required. You can't modify fields if they're marked final,
so GWT ignores final fields.
Don't forget that whatever approach is used it needs to (a) support
class hierarchies and (b) be translatable to javascript and (c) work in
the general case. That's why the gwt serialization rules are the way
they are.
If you don't like the rules, you can always create a custom field
serializer for each class and handle the serialization yourself.
Paul
On 25/09/10 17:31, Lucas Charron wrote:
I am having a slight problem with a framework I am making. Here is an
example class:
public class Example implements IsSerializable
{
private final int a;
private final int b;
public Example(int a,int b)
{
this.a=a;
this.b=b;
}
// getters ...
}
A very simple class. However, there is no way to serialize it using
GWT. Although the simple work-around is to remove the "final"
attribute from the fields, that does not "jive" with, what I consider,
solid programming. The "final" attribute means that no where, in any
instance of the class or any instance of a descendant of this class,
will the values of "a" and "b" be modified in any way (exception:
using Java reflection). More than the optimization that many JVMs will
do, there is also a type of safety - the programmer cannot
accidentally put the reference on the left hand side of an assignment
operator.
The GWT compiler will emit a warning that the final fields will not be
serialized. Using the "_CustomFieldSerializer" is also impossible
because the deserialize method takes an instance of the class you are
deserializing as a parameter - instead it should have the return value
as an instance of the class.
So, other than removing the final attribute, has anyone had any luck
side-stepping this issue? Anyone know of any bug reports or
enhancement requests for this (I have searched, but have come up
empty).
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