apache/dubbo · error · RuntimeException

${cause.message}

Error message

${cause.message}

What it means

Thrown by ClassGenerator.toClass() when javassist cannot turn the generated bytecode into a Class. NotFoundException means a referenced class/method/field could not be found during compilation; CannotCompileException means the generated method bodies violated JVM or javassist constraints. Both are rewrapped as RuntimeException(cause.message, cause).

Source

Thrown at dubbo-common/src/main/java/org/apache/dubbo/common/bytecode/ClassGenerator.java:370

                        String[] sn = mCtc.getSimpleName().split("\\$+"); // inner class name include $.
                        mCtc.addConstructor(
                                CtNewConstructor.make(code.replaceFirst(SIMPLE_NAME_TAG, sn[sn.length - 1]), mCtc));
                    }
                }
            }

            try {
                return mPool.toClass(mCtc, neighborClass, loader, pd);
            } catch (Throwable t) {
                if (!(t instanceof CannotCompileException)) {
                    return mPool.toClass(mCtc, loader, pd);
                }
                throw t;
            }
        } catch (RuntimeException e) {
            throw e;
        } catch (NotFoundException | CannotCompileException e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }

    public void release() {
        if (mCtc != null) {
            mCtc.detach();
        }
        if (mInterfaces != null) {
            mInterfaces.clear();
        }
        if (mFields != null) {
            mFields.clear();
        }
        if (mMethods != null) {
            mMethods.clear();
        }
        if (mConstructors != null) {
            mConstructors.clear();

View on GitHub (pinned to 3a3043227f)

Solutions

  1. Inspect getCause(): NotFoundException => add the missing class jar to the classpath; CannotCompileException => fix the generated method descriptor.
  2. Ensure every interface and its parameter/return types are loadable by the classloader passed to getProxy/mixin.
  3. Reduce the interface surface or split proxies so each references resolvable types.
  4. Reproduce with Proxy.getProxy(YourInterface.class) in a unit test to isolate the failing interface.

Example fix

// before
Proxy p = Proxy.getProxy(MissingDepsInterface.class); // references absent types

// after
// add the jar providing MissingDepsInterface's parameter types, then:
Proxy p = Proxy.getProxy(MissingDepsInterface.class);
Defensive patterns

Strategy: try-catch

Validate before calling

for (Class<?> ic : ics) {
    for (Method m : ic.getMethods()) {
        for (Class<?> pt : m.getParameterTypes()) {
            Class.forName(pt.getName(), false, loader); // throws if a referenced type is missing
        }
    }
}

Try / catch

try {
    Proxy.getProxy(ics);
} catch (RuntimeException e) {
    Throwable c = e.getCause();
    if (c instanceof javassist.NotFoundException) { /* missing class */ }
    else if (c instanceof javassist.CannotCompileException) { /* bad bytecode */ }
}

Prevention

When it happens

Trigger: Calling ccp.toClass(...) on a ClassGenerator whose added methods/fields reference classes missing from the pool, or whose generated source text is malformed (bad descriptors, duplicate methods, illegal bytecode).

Common situations: Dubbo Proxy/Mixin generation against interfaces whose referenced types are not visible to the generating ClassLoader; a method signature using a class not on the classpath; conflicting method overloads producing duplicate bytecode; very large generated classes hitting JVM limits.

Related errors

AI-assisted analysis of apache/dubbo@3a3043227f (2026-08-14). Data as JSON: /api/errors/fbd646fb44f74e46. Report an issue: GitHub.