WIP - troubleshooting 404 in Spring MVC 4

troubleshooting 404 in Spring MVC.md

Spring 4 - 404 troubleshooting

See https://www.baeldung.com/spring-handler-mappings - explains BeanNameUrlHandlerMapping, SimpleUrlHandlerMapping

Debug DispatcherServlet - DispatcherServlet.getHandler

• this.handlerMappings - I have 5 incl. (each has a pathMatcher: AntPathMatcher https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/util/AntPathMatcher.html which has . match(String pattern, String path))
  • RequestMappingHandlerMapping,
    • mappingRegistry.urlLookup and .mappingLookup -> controller methods
  • BeanNameUrlHandlerMapping,
    • handlerMap (empty)
  • SimpleUrlHandlerMapping,
    • urlMap has the mappings for static resourced added via ResourceHandlerRegistry
  • 2 EmptyHandlerMapping

Why is a mapping from URL -> controller missing? In org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#initHandlerMethods see the detected beanNames (all beans) and the isHandler check a few lines down. -> detectHandlerMethods -> this.mappingRegistry.register

=> info or debug or trace logs on org.springframework.web.servlet.handler.AbstractHandlerMethodMapping

Upon request:

• org.springframework.web.servlet.DispatcherServlet#doService -> doDispatch calls getHandler, which looks into this.handlerMappings
• org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#getHandlerMethods -> .MappingRegistry#getMappings -> this.mappingLookup
• org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#getHandlerInternal

beanName requestMappingHandlerMapping sees only 39 beanNames => 12 in mappingLookup, 25 in urlLookup

Docs: beans defined in the parent context are accessible in the child contexts - but the mapping does not search the parent context by default

Why isn't a css/js/.. resource found?

(Presumably added via WebMvcConfigurationSupport.addResourceHandlers(ResourceHandlerRegistry)) => Is the mapping as expected in the mappingRegistry? (see the previous section) If it is:

Debug lookup in the SimpleUrlHandlerMapping- debug org.springframework.web.servlet.handler.AbstractUrlHandlerMapping#getHandlerInternal - see lookupPath, drill down to lookupHandler() - here it runs getPathMatcher().match(registeredPattern, urlPath)
-> org.springframework.web.servlet.resource.ResourceHttpRequestHandler#handleRequest -> getResource() which tries to find the resource on the classpath / ...
-> org.springframework.web.servlet.resource.PathResourceResolver#getResource(java.lang.String, java.util.List<? extends org.springframework.core.io.Resource>)

NOTE: Inside org.springframework.web.servlet.handler.AbstractUrlHandlerMapping#lookupHandler look at the call to getPathMatcher().extractPathWithinPattern

lookupPath=/myapp/assets-verMS4wLjAtU05BUFNIT1Q=/myapp.css RESOURCE PATH=assets-verMS4wLjAtU05BUFNIT1Q=/myapp.css

AntPathMatcher.extractPathWithinPattern("/myapp/assets-ver{hash:.+?}/**/*", "/myapp/assets-verMS4wLjAtU05BUFNIT1Q=/myapp.css") => does stupid patternPart.indexOf('*') > -1 || patternPart.indexOf('?') check