Cannot perform conversion to XML from legacy HTML:

错误信息:Cannot perform conversion to XML from legacy HTML: The nekoHTML library is not in classpath. nekoHTML 1.9.15 or newer is required for processing templates in “LEGACYHTML5” mode [http://nekohtml.sourceforge.net]. Maven spec: “net.sourceforge.nekohtml::nekohtml::1.9.15”. IMPORTANT: DO NOT use versions of nekoHTML older than 1.9.15.
1、在application.properties中增加
spring.thymeleaf.content-type=text/html
spring.thymeleaf.cache=false
spring.thymeleaf.mode =LEGACYHTML5
2、添加依赖

<dependency>

<groupId>net.sourceforge.nekohtml</groupId>

<artifactId>nekohtml</artifactId>

<version>1.9.22</version></dependency>问题解决，关键是第2步添加依赖，因为第一步在使用thymeleaf时都会进行相关的配置。