Reflection - Passing Connection field to private method

Question

How with reflection do I pass a method parameter com.ibm.as400.access.AS400JDBCConnection to the following method:

    private String test1(Connection con){

    return "test1";
}

When I pass from my JUnit to the test1(con) I get the following error. java.lang.NoSuchMethodException: com.action.TestAction.test1(com.ibm.as400.access.AS400JDBCConnection)

I created another method:

    private String test2(com.ibm.as400.access.AS400JDBCConnection con){

    return "test2";
}

Run with test2(con) and it runs fine. Any input would be greatly appreciated on proper passing into test1 without alteration to the method.

==========================================================

The following is the example link I pulled from: Any way to Invoke a private method?

The following is my JUnit test:

@Test
public void testReturnScreen(){


    System.out.println("connection: "+con.getClass());
    System.out.println((String) genericInvokMethod(creditCardAction, "test2", 1, con));
    System.out.println((String) genericInvokMethod(creditCardAction, "test1", 1, con));

}

public static Object genericInvokMethod(Object obj, String methodName,
        int paramCount, Object... params) {
    Method method;
    Object requiredObj = null;
    Object[] parameters = new Object[paramCount];
    Class<?>[] classArray = new Class<?>[paramCount];
    for (int i = 0; i < paramCount; i++) {
        parameters[i] = params[i];
        classArray[i] = params[i].getClass();
    }
    try {
        method = obj.getClass().getDeclaredMethod(methodName, classArray);
        method.setAccessible(true);
        requiredObj = method.invoke(obj, parameters);
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    }

    return requiredObj;
}

Does the AS400JDBCConnection extend Connection, and can you show the code that calls the method by reflection? — Morfic, Oct 18 '13 at 19:12
Sorry for being so brief. It is a java.sql.Connection - Interface. I did an edit on the original message above — ogottwald, Oct 18 '13 at 20:23

Morfic · Accepted Answer · 2013-10-18T21:09:50.247

If con is of type AS400JDBCConnection, then getDeclaredMethod(methodName, classArray) will find nothing since your test1 method is defined with a Connection formal parameter, so it will throw the exception.

I think you could alter your genericInvokeMethod to something like:

public static Object genericInvokMethod(Object obj, String methodName, Object[] formalParams, Object[] actualParams) {
    Method method;
    Object requiredObj = null;

    try {
        method = obj.getClass().getDeclaredMethod(methodName, formalParams);
        method.setAccessible(true);
        requiredObj = method.invoke(obj, actualParams);
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    }

    return requiredObj;
}

... and invoke it like:

System.out.println((String) genericInvokMethod(creditCardAction, "test1", new Object[]{Connection.class}, new Object[]{con}));

I haven't tested whether the code compiles, but you get the idea.

Also if you could provide more info on what you're trying to achieve, perhaps we could bypass reflection and come up with a more elegant solution. — Morfic, Oct 18 '13 at 21:13
That worked! Thank you - I'm calling a private method in a Struts Action passing a number of parameters. I don't want to duplicate the code and I don't want to change the Action. Also using EasyMock and getting an issue on class $Proxy5 from are above example but that is another POST I think. — ogottwald, Oct 18 '13 at 22:41

Reflection - Passing Connection field to private method

1 Answers1