quarkusio/quarkus · error · IllegalArgumentException

Invalid URL:

Error message

Invalid URL: 

What it means

Thrown from MemoryClassPathElement.getUrl when constructing the quarkus: memory URL for an in-memory resource fails with MalformedURLException, and rethrown as IllegalArgumentException. The quarkus: protocol relies on MemoryUrlStreamHandler being registered; URL construction should normally succeed. Receiving this means the URL factory infrastructure was unavailable or the path was malformed.

Source

Thrown at independent-projects/bootstrap/core/src/main/java/io/quarkus/bootstrap/classloading/MemoryClassPathElement.java:95

            @Override
            public ClassPathElement getContainingElement() {
                return MemoryClassPathElement.this;
            }

            @Override
            public String getPath() {
                return name;
            }

            @Override
            public URL getUrl() {
                String path = "quarkus:" + name;
                try {
                    URL url = new URL(null, path, new MemoryUrlStreamHandler(resources.get(name), lastModified));

                    return url;
                } catch (MalformedURLException e) {
                    throw new IllegalArgumentException("Invalid URL: " + path);
                }
            }

            @Override
            public byte[] getData() {
                return res;
            }

            @Override
            public boolean isDirectory() {
                return false;
            }
        };
    }

    @Override
    public Set<String> getProvidedResources() {
        return resources.keySet();

View on GitHub (pinned to e1c734241f)

Solutions

1. Ensure MemoryURLStreamHandlerFactory is installed (URL.setURLStreamHandlerFactory) before creating memory class path elements
2. Check the resource name for invalid URL characters
3. Run within standard Quarkus bootstrap which installs the factory automatically

Example fix

// before
URL.setURLStreamHandlerFactory(new TomcatURLStreamHandlerFactory()); // displaces quarkus handler
// after
URL.setURLStreamHandlerFactory(new MemoryURLStreamHandlerFactory()); // or composite factory including it

try {
    new URL(null, "quarkus:" + name, new MemoryUrlStreamHandler(bytes, lastModified));
} catch (MalformedURLException e) { /* handler factory missing or bad name */ }

boolean isMemoryUrlSupported(String name) {
    return URL.getURLStreamHandler("quarkus") != null
        && name.chars().allMatch(c -> c > 32 && c < 127);
}

try {
    URL url = element.getUrl();
} catch (IllegalArgumentException e) {
    throw new IllegalStateException("Memory URL support unavailable; install MemoryURLStreamHandlerFactory", e);
}

When it happens

Trigger: Calling getUrl() on a MemoryClassPathElement when new URL(null, "quarkus:"+name, handler) throws MalformedURLException — typically because the MemoryURLStreamHandlerFactory was never installed on the URL stream handler factory.

Common situations: Tests or embedded usage that create MemoryClassPathElement instances without registering the memory URL stream handler factory; name containing characters that break URL parsing.

Related errors

• is being listed both as never loaded and as at most once
• never loaded class listed multiple times:
• resource listed multiple times as loaded at most once:
• Unable to create protection domain for
• Failed to translate

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/fc206390c58ad96c. Report an issue: GitHub.