java.lang.IllegalArgumentException: argument type mismatch while using Reflection

Question

Below is my code from which I am using reflection to call a method but I am always getting exception

List<PdAttrKey> attrKeys = new ArrayList<PdAttrKey>();
Properties adapterProps = new Properties();

PdReadRequest pdReadRequest = new PdReadRequest(1L, 1L, (short) 0, new Date(),
dataDurationSec, 2L, 3L, attrKeys, null, adapterProps);

PdAdapterUserReadOnlyGemsReader adapter1 = new PdAdapterUserReadOnlyGemsReader();

PdReader reader = adapter1.acquireReader(pdReadRequest);

UserCacheDoImpl userDos = Some Value;

Method method = getClassMethod("createPdRecordFromUserDO");

// This line is throwing me exception. And I don't know why?
PdRecord onePdsxRecord = (PdRecord) method.invoke(reader, userDos);

This is the below method from which I am getting all the method names of a class.

    private Method getClassMethod(String methodName) {
        Method method = null;

        Method[] methodList = PdAdapterUserReadOnlyGemsReader.PdUserReadOnlyGemsReader.class
                .getDeclaredMethods();
        for (Method m : methodList) {
            if (m.getName().equals(methodName)) {
                method = m;
                method.setAccessible(true);
                break;
            }
        }

        return method;
    }

Some More Code:-

private PdRecord createPdRecordFromUserDO(UserCacheDoImpl userCache) {
   // Some code here
}

This is the exception I am getting. Any idea why?

java.lang.IllegalArgumentException: argument type mismatch
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
    at java.lang.reflect.Method.invoke(Method.java:599)

Any suggestions will be of great help.

Answer 1

Please check if more than one method with name "createPdRecordFromUserDO" exists. It looks like there are more than one, but with different arguments.

Your method getClassMethod returns the first method it finds, but that could be the wrong one. Check if methodList.length > 1, then this is the cause of the bug.

Rethink what you want to do if multiple methods with the given name are found.