Replace Variables with issue as empty String about thymeleaf HOT 1 OPEN

I do not know if I understand your problem correctly but as this setup is using OGNL please make sure to include the adequate dependency of ognl:ognl (for Thymeleaf 3.1.2 its OGNL 3.3.4)

It is unclear what your replaceCustomVariableSyntax(templateString); method does but I guess it replaces the {{customer.name}} with something OGNL can handle like [[${customer.name}]] so that the final template string looks something like <p>Hello, [[${customer.name}]] !</p>

When you add customer. as a variable, there is no customer, thus the lookup of customer.name in your template fails with a null pointer exception. If you want an empty string, just use safe navigation:

<p>Hello, [[${customer} ? ${customer.name}]] !</p>

This will succeed even when customer is not set in the context.

from thymeleaf.