Resolving Thymeleaf Template Not Found Errors in Spring Boot 3.4.3 When Running as a JAR

The author revisits Spring Boot configuration to provide a Thymeleaf template engine for a small project, noting that while development environments (Eclipse, IDEA, VSCode) work fine, the packaged JAR fails to locate template resources.

Environment details: Spring Boot version 3.4.3, Java JDK 17. The failure manifests as org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [static//catch/catch-index.html]") .

To address the issue, the author defines the template resolver and engine directly in Java configuration, avoiding reliance on application.yml settings that may conflict when WebMvcConfigurer is implemented.

/** * Thymeleaf template resolver * @return */ @Bean public ITemplateResolver templateResolver() { SpringResourceTemplateResolver resolver = new SpringResourceTemplateResolver(); resolver.setPrefix("classpath:/static/"); resolver.setSuffix(".html"); resolver.setTemplateMode("HTML"); resolver.setCharacterEncoding("UTF-8"); resolver.setCacheable(false); return resolver; } /** * Spring template engine * @param templateResolver * @return */ @Bean public TemplateEngine templateEngine(ITemplateResolver templateResolver) { SpringTemplateEngine templateEngine = new SpringTemplateEngine(); templateEngine.setTemplateResolver(templateResolver); return templateEngine; }

The author also comments out Thymeleaf-related sections in application.yml to prevent conflicting configurations.

When returning a ModelAndView , the path should not start with a leading slash. The corrected controller method is:

@RequestMapping("/catch") public ModelAndView catch(@RequestParam(value="code", required=false) String code) { //ModelAndView mv = new ModelAndView("/catch/catch-index.html"); ModelAndView mv = new ModelAndView("catch/catch-index.html"); return mv; }

With these adjustments, the application runs successfully from the JAR, and the template is correctly resolved.

Key takeaways: 1) If WebMvcConfigurer is implemented, avoid configuring Thymeleaf in application.yml . 2) In ModelAndView , omit the leading slash in the view name.