Resource handling is inconsistent across different embedded containers

[wilkinsona]

The behaviour of embedded Tomcat, Jetty, and Undertow is inconsistent when the containers themselves are dealing with static resources, i.e. when Spring MVC's resource handling isn't involved. For example, support for loading resources from META-INF/resources of nested jars works with Tomcat but doesn't work with Undertow. Furthermore, I believe it only works with Tomcat when Jasper's on the classpath.

[wilkinsona]

Expectations

Fat war

For war files, we're interested in resources in these three locations:

app.war
├── META-INF
│   └── resources
│       └── meta-inf-resource.txt
├── WEB-INF
│   └── lib
│       └── resources.jar
│           └── META-INF
│               └── resources
│                   └── nested-meta-inf-resource.txt
└── resource.txt

Accessing resources via HTTP and via the servlet context (SC) should have the following results:

Path	Method	Result
/nested-meta-inf-resources.txt	HTTP	200
/nested-meta-inf-resources.txt	SC	URL
/meta-inf-resources.txt	HTTP	404
/meta-inf-resources.txt	SC	Null
/resource.txt	HTTP	200
/resource.txt	SC	URL

Fat jar

For jar files, we're interested in resources in these locations:

app.jar
├── BOOT-INF
│   └── lib
│       └── resources.jar
│           └── META-INF
│               └── resources
│                   └── nested-meta-inf-resource.txt
├── META-INF
│   └── resources
│       └── meta-inf-resource.txt
└── resource.txt

Accessing resources via HTTP and via the servlet context should have the following results:

Path	Method	Result
/nested-meta-inf-resources.txt	HTTP	200
/nested-meta-inf-resources.txt	SC	URL
/meta-inf-resources.txt	HTTP	404
/meta-inf-resources.txt	SC	Null
/resource.txt	HTTP	404
/resource.txt	SC	404

Actual behaviour

Fat war

Path	Method	Jetty	Tomcat	Undertow
/nested-meta-inf-resources.txt	HTTP	❌	❌/✅ (1)	❌
/nested-meta-inf-resources.txt	SC	❌	❌/✅ (1)	❌
/meta-inf-resources.txt	HTTP	✅	✅	✅
/meta-inf-resources.txt	SC	✅	✅	✅
/resource.txt	HTTP	✅	✅	✅
/resource.txt	SC	✅	✅	✅

(1) - Tomcat only works when Jasper in on the classpath

Fat jar

Path	Method	Jetty	Tomcat	Undertow
/nested-meta-inf-resources.txt	HTTP	❌	❌/✅ (1)	❌
/nested-meta-inf-resources.txt	SC	❌	❌/✅ (1)	❌
/meta-inf-resources.txt	HTTP	✅	✅	✅
/meta-inf-resources.txt	SC	✅	✅	✅
/resource.txt	HTTP	✅	✅	✅
/resource.txt	SC	✅	✅	✅

(1) - Tomcat only works when Jasper in on the classpath

[wilkinsona]

We should consider configuring the containers such that they can serve resources from BOOT-INF/classes/META-INF/resources. This would allow a jar-packaged project to place static resources in src/main/resources/META-INF/resources rather than having to move them out into a separate project that's depended upon (see #8324). A war file doesn't have this problem as war projects can place resources directly in src/main/webapp from where they'll end up in the root of the war.

[bjorntj]

Just wondering, where should I put static resources when using embedded Undertow? I have created a jar file that contains these resources and this is working fine when unsing tomcat or jetty, but undertow does not find the resources.
Or is a fix for this issue imminent?

[wilkinsona]

As long as you're using the latest version of 1.4.x and 1.5.x, it should work the same way in all three embedded containers. If you've found a situation where that's not the case, please open a new issue with a small sample that reproduces the problem.