ASP.NET is written and runs on the top of .NET framework, whereas Spring framework runs on a Java framework;
Java EE. Converting one to another is not possible, because there may be many differences in the frameworks. Even if you can find a tool to convert one to another, you are going to fix most of the errors yourself, which would be raised later.
The thing is, Java and .NET are different in many ways.
1. Their bytecodes have different standards.
2. A feature of one, may not be implemented in a similar manner in the other framework.
Microsoft used to create tools for converting Java code to J#, but even that was not guaranteed to convert 100% code to J#, that was also very long ago. Things are much complex now.
My recommendation is to build the application yourself, start by learning Spring framework and then write the same application in a different framework; Spring MVC framework.
Spring Framework Reference Documentation[
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