Loading template group from STGroupDir in app running on Tomcat 8 fails

[Mooninaut]

StringTemplate version: 4.3.1

I'm migrating a web application from Tomcat 7 to Tomcat 8. It appears something in the class loader behavior has changed between the versions.

My app calls STGroupDir group = new STGroupDir("com/example/app/path/to/templates");

When running on Tomcat 7, after the line root = cl.getResource(dirName); at STGroupDir.java:72 the variable root has the value

jar:file:/path/to/exploded/app/WEB-INF/lib/my-component.jar!/com/example/app/path/to/templates

Running on Tomcat 8, root has the value

jar:file:/path/to/exploded/app/WEB-INF/lib/my-component.jar!/com/example/app/path/to/templates/

My app then calls ST st = group.getInstanceOf("/TemplateGroup/someTemplate"); to load someTemplate from ...path/to/templates/TemplateGroup.stg.

When load() calculates groupFileURL on line STGroupDir.java:128, the value is

jar:file:/path/to/exploded/app/WEB-INF/lib/my-component.jar!/com/example/app/path/to/templates//TemplateName.stg

The double slash prevents it from successfully loading the template group file, and getInstanceOf() returns null.

[parrt]

oh wow. Sorry about that. I'm probably not joining paths correctly. I'm currently focused on 1 billion other things but I would welcome a PR if you have time.

[Mooninaut]

@parrt I've submitted a PR to fix this and #276. Please let me know what you think!

[parrt]

I see that root = cl.getResource(dirName); at line 74 not 72. I wonder if we are looking at different versions of the software something. sorry for the hassles. I'm just trying to understand exactly what's going on and I haven't looked at the software in years. haha

[parrt]

line 128 in STGroupDir is the issue:

groupFileURL = new URI(root+parent+GROUP_FILE_EXTENSION).normalize().toURL();

which looks to be what you are fixing in your PR. I wonder if we can just use a proper URL or file path "join" to avoid the extra code with the special tests that you've created.

[Mooninaut]

There is no simple URL/URI path join API in Java 1.6. The first line of STGroup.lookupTemplate() adds a leading / to the path, so root.resolve(parent + GROUP_FILE_EXTENSION) will treat parent as an absolute path, and strip the path from root. Now, STGroupDir.load() could remove that leading / and call resolve(), but at that point why bother? The URL/URI resolving code is very, very complex.

I've updated the PR to be more general, moving the logic to Misc.joinPathSegments() and testing that.

[parrt]

I would imagine we can move to Java 7 or 8 at this point. Is there something we can rely on in the new versions of Java?

[Mooninaut]

I tried a Java 7 implementation using NIO at https://github.com/Mooninaut/stringtemplate4/tree/java1.7 , but it causes several dozen tests to fail on Windows. I don't know that it's worth it.

[parrt]

I didn't see any changes in that fork of yours but have you seen this that was linked to from the documentation?

https://maven.apache.org/plugin-developers/common-bugs.html#Converting_between_URLs_and_Filesystem_Paths

I'm going to look in there as well

[parrt]

What if we simply removed '//' from any URL string? @Mooninaut

[parrt]

I just pushed a new snapshot of 4.3.2 via maven. can you give it a try?

[Mooninaut]

Works great!

[parrt]

hooray!