This problem occurs when spring boot} integrates thymeleaf
By querying other people’s blogs. I understand that there are several possible errors
1 when the method corresponding to your controller layer returns the HTML path and name, add an additional /.
For example, return “/index”. If this ‘/’ causes an error, the solution is to remove the ‘/’ in front of the return, such as return “/index”
2. Introduction package problem (I solved it this way)
Add dependency in porn
<dependency>
<groupId>net.sourceforge.nekohtml</groupId>
<artifactId>nekohtml</artifactId>
<version>1.9.22</version>
</dependency>