What have been done:

1. Fixed a Thymeleaf error in getting template.

Problems encountered:

1. An example of Thymeleaf ERROR:
   2020-02-03 22:35:27.782 [scheduling-1] ERROR org.thymeleaf.TemplateEngine - [THYMELEAF][scheduling-1] Exception processing template “”: Error resolving template [], template might not exist or might not be accessible by any of the configured Template Resolvers org.thymeleaf.exceptions.TemplateInputException: Error resolving template [], template might not exist or might not be accessible by any of the configured Template Resolvers

Root cause:

1. TemplateEngine has not been initialized before used.

Solution:

1. private TemplateEngine templateEngine = new TemplateEngine();