Passing Argument as object to invoke

Question

    String className = "com.endpoints.EndPointImpl"; 
    String methodName = "add";
    String args = "2,3";


    try {

        Class<?> clas = Class.forName(className);
        Object obj = Class.forName(className).newInstance(); 
        java.lang.reflect.Method method = null;
        //Type[] types;

        for(java.lang.reflect.Method m :obj.getClass().getMethods())
        {
            if(m.getName().equals(methodName))
            {
                method = m;
                //types = m.getParameterTypes();
                break;
            }
        }

//java.lang.reflect.Method method = clas.getDeclaredMethod(methodName,t);


        Object[] strarr =  args.split(",");

        Object retobj = method.invoke(obj,strarr );

how to i pass arguments to invoke as of now it is generating exception i know why but how can i pass two int

add(in,int)

PS

ArrayList<Object> objArr = new ArrayList<Object>();

        for(java.lang.reflect.Method m :obj.getClass().getMethods())
        {
            if(m.getName().equals(methodName))
            {
                method = m;

                int index = 0;
                for(Type type :m.getGenericParameterTypes())
                {
                    if(type.getClass().equals("Integer"))
                    {
                        objArr.add(Integer.parseInt(strarr[index]));
                    }
                    else if(type.getClass().equals("Float"))
                    {
                        objArr.add(Float.parseFloat(strarr[index]));
                    }
                    index++;
                }

and then pass the objArr in invoke or there is a better solution, i want to also ask if it is possible to create a generic convert function so that it will conver the string to specified type

Answer 1

When writing code, you should always ask yourself what you should be doing. The best way to answer this is to read the Javadoc. Also, please always provide full stacktraces when you get exceptions. You don't need your whole for loop.

Use Method#getDeclaredMethod(String, Class[]) . It accepts two arguments

name - the name of the method
parameterTypes - the parameter array

If the method is named add and accepts two int arguments, call it like this

java.lang.reflect.Method method = clas.getDeclaredMethod("add", int.class, int.class);

The int.class arguments are the type of parameters the method takes.

You can invoke the method with

method.invoke(object, 3, 3);

where object is an instance of the class declaring add(int, int) method. If this method is static , you could pass null instead. The two 3 s are the int argument values you would pass as if you were calling the method directly.

object.add(3,3);

If you are receiving Strings to pass in as arguments, you need to cast them first

String args = "2,3";
String[] strarr =  args.split(",");
// with no other validation
int[] values = new int[strarr.length];
for (int i = 0; i < strarr.length; i++) {
    values[i] = Integer.parseInt(strarr[i]);
}

method.invoke(object, values);

Obviously, perform the appropriate validation when splitting and parsing the Strings.

Answer 2

1. Replace this statement String args = "2,3"; with Integer args = {10,20};
2. Remove this statement Object[] strarr = args.split(",");
3. Replace Object retobj = method.invoke(obj,strarr ); with Object retobj = method.invoke(obj,args);