Error while configuring View Resolver for mustache template engine - spring-boot

Question

I have the following configuration file in spring-boot project :
#Configuration
public class AppConfig {
#Bean
public ViewResolver mustacheViewResolver() {
MustacheViewResolver viewResolver = new MustacheViewResolver();
viewResolver.setPrefix("/templates/");
viewResolver.setSuffix(".mustache");
viewResolver.setOrder(1);
return viewResolver;
}
}
When I run my application, I am getting the following error:
Description:
The bean 'mustacheViewResolver', defined in class path resource [org/springframework/boot/autoconfigure/mustache/MustacheServletWebConfiguration.class], could not be registered. A bean with that name has already been defined in class path resource [com/example/demo/AppConfig.class] and overriding is disabled.
Action:
Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true
I am not sure if I am configuring the view Resolver properly
Error after removing the configuration class:
o.s.w.s.v.ContentNegotiatingViewResolver : Selected '*/*' given [*/*]
o.s.w.servlet.view.InternalResourceView : View name 'tweets.mustache', model {tweets=null}
o.s.w.servlet.view.InternalResourceView : Forwarding to [tweets.mustache]
o.s.web.servlet.DispatcherServlet : "FORWARD" dispatch for GET "/tweets.mustache?email=tim#gmail.com", parameters={masked}
o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped to ResourceHttpRequestHandler [classpath [META-INF/resources/], classpath [resources/], classpath [static/], classpath [public/], ServletContext [/]]
o.s.w.s.r.ResourceHttpRequestHandler : Resource not found
o.s.web.servlet.DispatcherServlet : Exiting from "FORWARD" dispatch, status 404
o.s.web.servlet.DispatcherServlet : Completed 404 NOT_FOUND
o.s.web.servlet.DispatcherServlet : "ERROR" dispatch for GET "/error?email=tim#gmail.com", parameters={masked}
s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#error(HttpServletRequest)
o.s.w.s.m.m.a.HttpEntityMethodProcessor : Using 'application/json', given [*/*] and supported [application/json, application/*+json, application/json, application/*+json]
o.s.w.s.m.m.a.HttpEntityMethodProcessor : Writing [{timestamp=, status=404, error=Not Found, path=/tweet2}]
o.s.web.servlet.DispatcherServlet : Exiting from "ERROR" dispatch, status 404
#GetMapping("/tweet2")
public ModelAndView getTweetsByEmail(#RequestParam String email) {
HQLExample.insertRecords();
ModelAndView modelAndView = new ModelAndView("tweets.mustache");
List<Tweet> tweets = tweetMap.get(email);
modelAndView.getModel().put("tweets",tweets);
return modelAndView;
}

Answer 1

Assuming you have added spring-boot-starter-mustache as a dependency (to easily include all needed dependencies). When Spring Boot detects Mustache on the classpath it will automatically configure the MustacheViewResolver which will load Mustache templates from /templates on the classpath. The files should end with .mustache.
With this in mind, just remove your AppConfig class as it interferes with the auto configuration.
In your controller the name of the view is the name you have but without the .mustache that will be added by the ViewResolver.
So in short you should remove things and it will work. Do more with less in this case.