Improve error message for unsupported character in SpEL expression

[sbrannen]

Overview

If the Spring Expression Language (SpEL) parser encounters a character that it does not support, the current error message is not very helpful.

For example, if an identifier (i.e., property name, variable name, etc.) contains a character with an umlaut such as ü, the error message is currently: Cannot handle (252) 'ü'.

In such cases, we should craft a more meaningful error message such as: Unsupported character 'ü' (252) encountered at position 13 in expression.

Related Issues

• Support letters other than A-Z in identifiers in SpEL expressions #30580