Issue #1592 Add support for JAR: URLs to OpenAPIV3Parser

[allen-ball]

Extended OpenAPIV3Parser.readLocation() to read content from a jar:jarfile-uri-spec!/spec.yml styled URL as described in #1592. Additional test included.

[clone1612]

I've tried this PR as it's a feature we'd like to use, but I get a NPE if the Swagger contains a reference to another schema within the JAR

io.swagger.v3.parser.OpenAPIV3Parser - Exception while resolving:
java.lang.NullPointerException: null
	at io.swagger.v3.parser.util.PathUtils.getParentDirectoryOfFile(PathUtils.java:30)
	at io.swagger.v3.parser.ResolverCache.<init>(ResolverCache.java:76)
	at io.swagger.v3.parser.OpenAPIResolver.<init>(OpenAPIResolver.java:38)
	at io.swagger.v3.parser.OpenAPIResolver.<init>(OpenAPIResolver.java:32)
	at io.swagger.v3.parser.OpenAPIV3Parser.resolve(OpenAPIV3Parser.java:176)
	at io.swagger.v3.parser.OpenAPIV3Parser.readContents(OpenAPIV3Parser.java:156)
	at io.swagger.v3.parser.OpenAPIV3Parser.readLocation(OpenAPIV3Parser.java:91)
	at io.swagger.parser.OpenAPIParser.readLocation(OpenAPIParser.java:16)

The actual exception leading up to it is an InvalidPathException (due to a ":" in the path) thrown in PathUtils that is ignored. Tweaking the ResolverCache constructor to not set a parentDirectory for jars seems to be enough to work around that:

        if(parentFileLocation != null) {
            if(parentFileLocation.startsWith("http") || parentFileLocation.startsWith("jar")) {
                parentDirectory = null;
            } else {
                parentDirectory = PathUtils.getParentDirectoryOfFile(parentFileLocation);
            }
        }

as during the loading of references it'll use the root path to load an external reference:

            if(parentDirectory != null) {
                contents = RefUtils.readExternalRef(file, refFormat, auths, parentDirectory);
            }
            else if(rootPath != null && rootPath.startsWith("http")) {
                contents = RefUtils.readExternalUrlRef(file, refFormat, auths, rootPath);
            }
            else if (rootPath != null) {
                contents = RefUtils.readExternalClasspathRef(file, refFormat, auths, rootPath);
            }

[allen-ball]

Thank you. I've made your suggested change and the tests ran successfully.

[gracekarina]

thanks for this feature.