从Java代码调用网站的javascript函数？

Question

Is it possible to use java code to invoke a javascript function that is in the sourcecode of a website?

Imagine a website with following code:

<script>
 function sayHello(name) {
    return "Hello " + name;
}
</script>

Could I call "sayHello" from a client connecting to that webpage? (I know I could call javascript from java if I have the *.js file locally saved. But I don't want this as the JS might change on the website I want to invoke the function).

 ScriptEngineManager factory = new ScriptEngineManager();
 ScriptEngine engine = factory.getEngineByName("JavaScript");
 engine.eval(..); //is it possible to invoke the JS function on the website?

Answer 1

I think you would have to parse content of script tags first (manually by fetching HTML page and then using eg RegExp find content of all script elements) and then pass it to the eval() as a string. Not pretty thing is that the JS code in <script> could be using some other JS code (external, loaded before this element etc.) so you might need to check for these "dependencies" as well.

Answer 2

您只能通过Ajax call或iframe refresh之类的老式方式来做到这一点

Answer 3

If I understood correctly you want to call existing JavaScript in website as well as add some logic yourself.

You don't have to use Java here at all, you can simply inject your JavaScript into that page by

1. bookmarklets

2. Browser extenstions I'd recommend Kango

3. Or simply pasting the code into the browser console