How to silently truncate strings while storing them when they are longer than the column length definition?

Question

I have a web app, using EclipseLink and MySQL for storing data. Some of these data are strings, ie varchars in the DB. In the code of entities, the strings have attributes

Answer 1

If you want to do this on a field-by-field basis rather than globally, then you might be able to make a custom type mapping that truncates the value to the given length before inserting it into the table. Then you can attach the converter to the entity by an annotation like:

@Converter(name="myConverter", class="com.example.MyConverter")

and to the relevant fields via:

@Convert("myConverter")

This is really meant for supporting custom SQL types, but it might work for normal varchar type fields as well. Here is a tutorial on making one of these converters.