Check javascript function is defined from java applet

Question

I am developing a Java applet where I call a javascript function:

boolean isAllowed = (boolean) win.eval("isPointMarkCreationAllowed()");

and I would like to check if that function exists, like we do in javascript:

if (isPointMarkCreationAllowed == 'function')

is there anyway to do that in Java?

win.eval("isPointMarkCreationAllowed()"); What happens when you call that and the function does not exist? I would expect a JSException according to the JavaDocs. — Andrew Thompson
– Andrew Thompson, Commented Jan 28, 2013 at 14:58

jarnbjo · Accepted Answer · 2013-01-28 14:56:43Z

2

Without actually having tried it, wouldn't

win.eval("typeof isPointMarkCreationAllowed == 'function'");

do exactly what you want and return a Boolean (true or false)?

answered Jan 28, 2013 at 14:56

jarnbjo

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Andrew Thompson Over a year ago

I suspect it would would the trick. If not, abstract out that code into a JS function that accepts the name of a function and returns true or false on evaluation.

Kakalokia · Accepted Answer · 2013-01-28 14:50:33Z

-1

You can use reflection to test if a method exists.

For example if you have an object foo, you can get all the methods declared in the class of that object in the following:

Method[] methods = foo.getClass().getMethods();

This returns an array of the methods declared in the class.

Then just use a for loop to check if a specific method exists in the array returned

for (Method m : methods)
{
     if (m.getName().equals(someString))
     {
        //do something
     }
}

someString is the name of the method you're looking for, which is "isPointMarkCreationAllowed" in your case.

Use the following site to learn about reflections in Java http://docs.oracle.com/javase/tutorial/reflect/member/methodType.html

answered Jan 28, 2013 at 14:50

Kakalokia

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1 Comment

jarnbjo Over a year ago

No, you can't use reflection to access or check JavaScript function from an applet.

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