ResourceUrlEncodingFilter fails when Thymeleaf and the "/**" resource pattern is used [SPR-12630]

[spring-projects-issues]

Christopher Savory opened SPR-12630 and commented

I could not get ResourceUrlEncodingFilter to work with Thymleaf templates. I believe the problem is that Thymleaf calls encodeURL on all of it's URLs, even standard links. What happens is that ResourceUrlEncodingFilter tries to look up resources of links and can't find them (because they don't exist, but are just mappings) and throws an exception.

I had to create my own filter based on ResourceUrlEncodingFilter that would only encode resources that had specific extensions I wanted encoded. It would be nice if ResourceUrlEncodingFilter used the same set of extensions supplied when the path patterns are supplied to ResourceHandlerRegistry.addResourceHandler and further, only those with a Transformer attached to it.

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Affects: 4.1.3

Referenced from: commits spring-attic/spring-framework-issues@25f7f0d

[spring-projects-issues]

Rossen Stoyanchev commented

The ResourceUrlProvider only tries to resolve paths that match the resource mappings. Is this with a "/\*\*" pattern for resource mappings vs something more specific like "/resources/\*\*"?

[spring-projects-issues]

Christopher Savory commented

Rossen, I think it might be related to spring-projects/spring-boot#2360, the Spring Boot WebMvcAutoConfiguration creates a mapping with ```
/**

[spring-projects-issues]

Rossen Stoyanchev commented

I've added a repro project for this https://github.com/spring-projects/spring-framework-issues/tree/master/SPR-12630. The thymeleaf template has links to main.js (an actual resource) and another link to "/foo/bar" which isn't a resource, I'm just looking how it will be rendered. The "/foo/bar" link fails:

 [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateProcessingException: Error during execution of processor 'org.thymeleaf.spring4.processor.attr.SpringHrefAttrProcessor' (greeting:10)] with root cause

java.lang.IllegalStateException: Failed to get public resource URL path for foo/bar
	at org.springframework.web.servlet.resource.ResourceUrlProvider.getForLookupPath(ResourceUrlProvider.java:211)
	at org.springframework.web.servlet.resource.ResourceUrlEncodingFilter$ResourceUrlEncodingResponseWrapper.encodeURL(ResourceUrlEncodingFilter.java:78)
	at org.thymeleaf.standard.expression.LinkExpression.executeLink(LinkExpression.java:378)

We raise an ISE if a link matches a resource pattern but is not actually resolved and of course the pattern "/**" will match to anything.

[spring-projects-issues]

Rossen Stoyanchev commented

One option would be to simply remove the IllegalStateException. The Javadoc doesn't contradict:

• @return the resolved public URL path, or {@code null} if unresolved

I suppose the intent of the exception was that if a given path actually matches a resource pattern it should resolve to an actual resource, but if the pattern is too general then that's proving to be too strict. We could try to see what kind of pattern it is but "too general" is a bit hard to define when it comes to Ant path patterns and the behavior would be inconsistent. So I propose simply dropping the check.

In the case of ResourceUrlEncodingFilter, the worse-case scenario is that the resource will still render but without changes (e.g. no version would be inserted). Hence logging would be required to track potential issues.