apache/druid · error · UnsupportedOperationException

Unable to create URL classpath entry

Error message

Unable to create URL classpath entry

What it means

Thrown by JvmUtils.systemClassPath when one of the entries of the java.class.path system property cannot be converted to a java.net.URL via Paths.get(s).toUri().toURL(), which throws MalformedURLException. The error is wrapped in UnsupportedOperationException with the original cause attached.

Solutions

1. Inspect the java.class.path property for the offending entry (the exception cause identifies it)
2. Start Druid with the standard druid launcher script rather than a custom -cp
3. Remove or quote unusual characters (spaces, wildcards, URL-style entries) from the classpath
4. If a path legitimately contains special characters, pass it as a proper filesystem path, not a URL string

Example fix

// before
java -cp "lib/*:conf/druid:file:/opt/my lib/x.jar" ...
// after
java -cp "lib/*:conf/druid:/opt/my\\ lib/x.jar" ...

for (String s : System.getProperty("java.class.path").split(File.pathSeparator)) {
  try { new java.io.File(s).toPath().toUri().toURL(); }
  catch (Exception e) { log.error("Bad classpath entry: {}", s); }
}

try {
  List<URL> urls = JvmUtils.systemClassPath();
} catch (UnsupportedOperationException e) {
  log.error("Classpath entry malformed, cause={}", e.getCause());
  throw e;
}

When it happens

Trigger: Running code that builds a classpath URL list (used for task/child-process classpaths) while java.class.path contains an entry that produces a malformed URI - typically entries with invalid characters (spaces in exotic setups, unclosed jar syntax like 'file:...!' references) or a null element in the paths array.

Common situations: Custom launcher scripts that assemble the classpath manually, environments where Druid is started with a hand-built -cp containing URLs or wildcard entries, OSGi-like containers injecting unusual classpath strings.

Understand the failure class

Background: "Invalid URL" / "URL cannot be empty": fix the malformed or missing URL behind request-construction failures — this error's family across 50 libraries.

Related errors

• 08001
• Bad URL
• Cannot determine maxDirectMemory from
• Cannot figure out default port for protocol
• Cannot load JDBC driver class

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/e2a610f23f846561. Report an issue: GitHub.

Appendix: source

Thrown at processing/src/main/java/org/apache/druid/utils/JvmUtils.java:138

    try {
      return function.get();
    }
    finally {
      accumulator.addAndGet(safeGetThreadCpuTime() - start);
    }
  }

  public static List<URL> systemClassPath()
  {
    List<URL> jobURLs;
    String[] paths = System.getProperty("java.class.path").split(File.pathSeparator);
    jobURLs = Stream.of(paths).map(
        s -> {
          try {
            return Paths.get(s).toUri().toURL();
          }
          catch (MalformedURLException e) {
            throw new UnsupportedOperationException("Unable to create URL classpath entry", e);
          }
        }
    ).collect(Collectors.toList());
    return jobURLs;
  }

  /**
   * Get the total memory of the machine it is running on. This function is container aware.
   * If the machine is running in a container, the function will return the total memory of the container.
   * If the machine is not running in a container, the function will return the total memory of the machine.
   * @return the total memory of the machine it is running on in bytes.
   */
  public static long getTotalMemory()
  {
    return OPERATING_SYSTEM_MX_BEAN.getTotalPhysicalMemorySize();
  }
}

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