a new UDF object is constructed every time there is a message

Hello Beamers, I want to ask a question about Beam SQL UDF. When I use the following statement to register UDF and execute sql,

SqlTransform.query("select capitalize([field]) from [bounded] right join [unbounded] on [condition]").registerUdf("capitalize", new SqlUDF.CapitalizeStringFn()));

from my observation, every time there is an incoming message, a new UDF object is constructed. Is there a way to make this UDF object to be just created once instead of unlimited times? Thank you very much!