apache/cassandra · error · CommandLine.InitializationException

Failed to create instance of

Error message

Failed to create instance of 

What it means

NodeTool's factory wraps any exception encountered while reflectively constructing and wiring a command bean (instantiating the class, setting injectable fields) into picocli's CommandLine.InitializationException with the class name as the message. It is a catch-all for reflection failures during command initialization.

Source

Thrown at src/java/org/apache/cassandra/tools/NodeTool.java:356

                        else if (field.getType().equals(Output.class))
                        {
                            field.setAccessible(true);
                            field.set(bean, output);
                        }
                        else
                        {
                            throw new RuntimeException("Unsupported injectable field type: " + field.getType() +
                                    " in class " + beanClass.getName() + ". " +
                                    "Only INodeProbeFactory and Output are supported.");
                        }
                    }
                }
                while ((beanClass = beanClass.getSuperclass()) != null);
                return bean;
            }
            catch (Exception e)
            {
                throw new CommandLine.InitializationException("Failed to create instance of " + cls, e);
            }
        }
    }
}

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Give the command class a public no-argument constructor
2. Fix the root cause exception (it is attached as the cause — inspect the stack trace)
3. Ensure constructor/injection code does not throw at construction time; defer work to execute()
4. Verify the command class and its injectable fields follow NodeTool's supported types

Example fix

// before
public MyCommand(String configPath) { ... }
// after
public MyCommand() { }
void execute() { String configPath = parseArgs(); ... }

// ensure a public no-arg constructor exists
if (java.lang.reflect.Modifier.isPublic(cls.getModifiers())
    && java.util.Arrays.stream(cls.getConstructors()).noneMatch(c -> c.getParameterCount() == 0))
    throw new IllegalStateException(cls + " needs a public no-arg constructor");

try { CommandLine cmd = factory.create(CommandClass.class); ... }
catch (CommandLine.InitializationException e) {
    LOG.error("Cannot init command " + e.getMessage() + ": " + e.getCause(), e);
}

When it happens

Trigger: Any exception while creating a NodeTool command instance: the command class has no accessible no-arg constructor, its constructor throws, an @Inject field is inaccessible/fails on set, or the unsupported-type RuntimeException from create() bubbles up here.

Common situations: Custom nodetool command with a constructor taking arguments; constructor code that throws (e.g. reading config at construction); obfuscation or module restrictions blocking setAccessible; the unsupported-injectable-type error being wrapped.

Related errors

• Failed to initialize command line hierarchy
• Unsupported injectable field type: in class . Only INodePro
• Invalid comparator class %s: must define a public static ins
• Properties specified %s are not understood by %s
• %s.validateOptions() threw an error: %s %s

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/91e00520741d2212. Report an issue: GitHub.