TemplateInputException with Thymeleaf 3.x on Spring Boot 1.5

Direct answer

Spring Boot 1.5 does not officially support the thymeleaf-spring5 integration. Spring Boot 2.0+ is the first line that bundles Spring Framework 5 and supports org.thymeleaf.spring5.SpringTemplateEngine. With Spring Boot 1.5 locked, you can use Thymeleaf 3.0.x only with the thymeleaf-spring4 integration. A NoSuchMethodError for org.thymeleaf.spring5.SpringTemplateEngine.process indicates thymeleaf-spring5 is on the classpath.

Confirmed facts

• Spring Boot 1.5.x is built on Spring Framework 4.3.x.
• The spring-boot-starter-thymeleaf auto-configuration for 1.5 wires org.thymeleaf.spring4.SpringTemplateEngine, not the spring5 package.
• org.thymeleaf.spring5.SpringTemplateEngine and the thymeleaf-spring5 module require Spring Framework 5.
• Spring Boot 2.0+ is the first version that officially supports the spring5 integration.

Likely explanation

A direct dependency on Thymeleaf 3.x is pulling in thymeleaf-spring5, while the Spring Boot 1.5 starter brings in thymeleaf-spring4 compatible artifacts. The mixed classpath causes the auto-configured SpringTemplateEngine bean to be created from the wrong module, and template processing fails with TemplateInputException wrapping NoSuchMethodError.

Recommended resolution for Spring Boot 1.5 locked

1. Keep Thymeleaf 3.0.x. Do not use Thymeleaf 3.1+ with Spring Boot 1.5; 3.1+ was designed for Spring 5 and thymeleaf-spring5.
2. Ensure only thymeleaf-spring4 is on the classpath. Explicitly exclude thymeleaf-spring5 from any dependency.
3. Maven example:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-thymeleaf</artifactId>
  <exclusions>
    <!-- let the starter manage Thymeleaf core version -->
  </exclusions>
</dependency>
<dependency>
  <groupId>org.thymeleaf</groupId>
  <artifactId>thymeleaf-spring4</artifactId>
</dependency>
<dependency>
  <groupId>org.thymeleaf</groupId>
  <artifactId>thymeleaf</artifactId>
  <version>3.0.x</version>
</dependency>

Do not declare thymeleaf-spring5. If a library transitively brings it in, add an exclusion for org.thymeleaf:thymeleaf-spring5.

1. Verify the classpath.

mvn dependency:tree -Dincludes=org.thymeleaf

Expected: thymeleaf 3.0.x and thymeleaf-spring4 present. thymeleaf-spring5 must be absent.

Check the instantiated engine class at runtime or in logs to confirm org.thymeleaf.spring4.SpringTemplateEngine.

Can you exclude and replace the transitive Thymeleaf?

Yes, but only with a Spring 4 compatible set. Excluding the starter's transitive Thymeleaf and replacing it with Thymeleaf 3.0.x + thymeleaf-spring4 is safe and preserves auto-configuration. Replacing it with a version that brings thymeleaf-spring5 breaks auto-configuration and produces the NoSuchMethodError. Mixing thymeleaf-spring4 and thymeleaf-spring5 jars on the same classpath can cause classloader conflicts even if startup succeeds.

Missing diagnostic detail that changes the recommendation: what exact Thymeleaf core version and which thymeleaf-spring artifact is present in your dependency tree right now. If you are on Thymeleaf 3.1+ the only safe path on Spring Boot 1.5 is to downgrade to Thymeleaf 3.0.x with thymeleaf-spring4.