alibaba/arthas · warning · IllegalAccessError

By default, strict mode is true, not allowed to set object p

Error message

By default, strict mode is true, not allowed to set object properties. Want to set object properties, execute `options strict false`

What it means

Thrown as IllegalAccessError by ArthasObjectPropertyAccessor.setPossibleProperty when GlobalOptions.strict is true (the default) and an OGNL expression tries to SET an object property (write). This is a deliberate safety guard: out-of-the-box Arthas forbids OGNL writes to objects to prevent accidental mutation of the live target application. The message itself (GlobalOptions.STRICT_MESSAGE) instructs the user how to opt out.

Source

Thrown at core/src/main/java/com/taobao/arthas/core/command/express/ArthasObjectPropertyAccessor.java:18

package com.taobao.arthas.core.command.express;

import java.util.Map;

import com.taobao.arthas.core.GlobalOptions;

import ognl.ObjectPropertyAccessor;
import ognl.OgnlException;

/**
 * @author hengyunabc 2022-03-24
 */
public class ArthasObjectPropertyAccessor extends ObjectPropertyAccessor {

    @Override
    public Object setPossibleProperty(Map context, Object target, String name, Object value) throws OgnlException {
        if (GlobalOptions.strict) {
            throw new IllegalAccessError(GlobalOptions.STRICT_MESSAGE);
        }
        return super.setPossibleProperty(context, target, name, value);
    }

}

View on GitHub (pinned to 21cf2e9ba5)

Solutions

Explicitly disable strict mode: run `options strict false` before the mutating expression.
Re-evaluate whether you really need to write — prefer read-only diagnostics; if you must mutate, accept the risk consciously.
Re-enable strict after: `options strict true`.

Example fix

// before
ognl '#this.enabled = true'   // throws under strict mode

// after
options strict false
ognl '#this.enabled = true'
options strict true

Defensive patterns

Strategy: validation

Validate before calling

if (GlobalOptions.strict && expressionIsWrite(ognlExpr)) {
    // either run `options strict false` or refrain from writing
}

Type guard

static boolean isStrictWriteBlocked() { return GlobalOptions.strict; }

Try / catch

try {
    Object r = ognlEngine.get/setValue(...);
} catch (IllegalAccessError e) {
    if (e.getMessage().equals(GlobalOptions.STRICT_MESSAGE)) {
        // instruct user to `options strict false` if write is intentional
    }
}

Prevention

Prefer read-only OGNL expressions for diagnostics.
Consciously toggle `options strict false` only when mutation is intended, then re-enable.
Document which expressions write so reviewers can catch accidental mutations.

When it happens

Trigger: Evaluate an OGNL expression that assigns to a property — e.g. '#this.field = x', 'target.foo = bar', or any lvalue assignment in watch/trace/ognl — while GlobalOptions.strict is at its default true.

Common situations: User attempts to mutate target state via ognl/watch without knowing strict mode is on; scripted diagnostics that try to flip a flag on the target; migrating from an older Arthas where strict was not enforced.

Related errors

AI-assisted analysis of alibaba/arthas@21cf2e9ba5 (2026-08-14). Data as JSON: /api/errors/c7e203db3011be52. Report an issue: GitHub.