How Can I Load Classpath Resources Using a Custom URL Protocol?

Using Classpath Protocol to Load Resources

Problem Statement:

Loading resources from the classpath using a URL protocol that does not require specifying the specific JAR file or class folder.

Solution:

Implementing a URL Stream Handler:

To create a protocol that loads resources from the classpath, implement a custom URLStreamHandler. This handler will open connections to URLs using the "classpath" protocol.

<br>public class Handler extends URLStreamHandler {</p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">private final ClassLoader classLoader;

public Handler(ClassLoader classLoader) {
    this.classLoader = classLoader;
}

@Override
protected URLConnection openConnection(URL u) throws IOException {
    final URL resourceUrl = classLoader.getResource(u.getPath());
    return resourceUrl.openConnection();
}

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}

Usage:

Use the custom handler to specify the classpath protocol in the URL when loading resources.

<br>new URL("classpath:org/my/package/resource.extension").openConnection();<br>

Handling Launch Issues:

Manual Code Handler Specification:

If possible, manually specify the custom handler when creating the URL.

<br>new URL(null, "classpath:some/package/resource.extension", new org.my.protocols.classpath.Handler(ClassLoader.getSystemClassLoader()))<br>

JVM Handler Registration:

Register a URLStreamHandlerFactory with the JVM to handle all URLs using the classpath protocol.

<br>URL.setURLStreamHandlerFactory(new ConfigurableStreamHandlerFactory("classpath", new Handler(ClassLoader.getSystemClassLoader())));<br>

Caveat:

JVM handler registration can only be called once per JVM, so be cautious when using it in environments where multiple handlers may conflict.

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