How can get methods like "method1.method2" ClassLoader?

Question

I am new in ClassLoader issue in Java. So how can i call methods like

getDefault().GetImage();

This is my current code:

ClassLoader tCLSLoader = new URLClassLoader(tListURL);
Class<?> tCLS = tCLSLoader.loadClass("com.github.sarxos.webcam.Webcam");

// MY FAILED TEST
Method tMethod = tCLS.getDeclaredMethod("getDefault().GetImage"); 
tMethod.invoke(tCLS,  (Object[]) null);

EDIT:

I tried this:

Method tMethod1 = tCLS.getDeclaredMethod("getDefault");
Object tWebCam = tMethod1.invoke(tCLS,  (Object[]) null);

// WebCam - Class
Class<?> tWCClass = tWebCam.getClass();


Method tMethod2 = tWCClass.getDeclaredMethod("getImage");
tMethod2.invoke(tWCClass, (Object[]) null);

But I get:

java.lang.IllegalArgumentException: object is not an instance of declaring class

I need to get this result:

BufferedImage tBuffImage = Webcam.getDefault().getImage();

Er, interesting. Not quite how Java works. What are you trying to do exactly? You certainly cannot do this. You need to know what the return type of `getDefault()` is, cast and then call the next method. — Boris the Spider, Jul 27 '13 at 22:23
You need to pass in the instance not the `Class` so `tMethod2.invoke(tWebCam, (Object[]) null);` — Boris the Spider, Jul 27 '13 at 22:37

score 1 · Accepted Answer · answered Jul 27 '13 at 22:42

You cannot do this, this is not how reflection works.

You need to split your String by . and then loop and invoke methods in turn.

This ought to work

private static Object invokeMethods(final String methodString, final Object root) throws Exception {
    final String[] methods = methodString.split("\\.");
    Object result = root;
    for (final String method : methods) {
        result = result.getClass().getMethod(method).invoke(result);
    }
    return result;
}

A quick test:

public static void main(String[] args) throws Exception {
    final Calendar cal = Calendar.getInstance();
    System.out.println(cal.getTimeZone().getDisplayName());
    System.out.println(invokeMethods("getTimeZone.getDisplayName", cal));
}

Output:

Greenwich Mean Time
Greenwich Mean Time

A class cannot be static, a method can be static. This should still work in that case, from the [JavaDoc](http://docs.oracle.com/javase/6/docs/api/java/lang/reflect/Method.html#invoke(java.lang.Object,%20java.lang.Object...)) _If the underlying method is static, then the specified obj argument is ignored. It may be null._ — Boris the Spider, Jul 27 '13 at 23:03

How can get methods like "method1.method2" ClassLoader?

1 Answers1