java applet: How to invoke/access javascript variable of web page from applet?

Question

An example:

getAppletContext().showDocument(
  new URL("javascript:alert(document.getElementById('textbox').value);"
));

Instead of alerting this textbox value, I want to use this value further as string variable in my applet program. How can i achieve this?

Answer 1

Multiple ideas for different approaches. Here are some:

---

Put the input-field in the Applet. Instead of adding an <input> -tag to the HTML-page, you can get input in the Applet by adding AWT components (or, when using a JApplet you can use the newer Swing toolkit) to it. Although Swing should be preferred.

Of course, if you can't change the applet-code, this is not an option.

---

Use the <param> -tag. You can give your applet some initial values (eg parameters), by using the <param> -tag in the <applet> -tag as shown by this example from the tag-doc :

<applet code="A21" width="256" height="256" archive="toir.jar">
  <param name="img" value="test.gif">
</applet>

However, as I said, these are initial values. If you change them while the applet is already running, they won't change in the Applet itself.

So, if the values in your <input> -tag are for initial values, you can use this (and manipulate the value -attribute with JS). If you want to change the values while the applet is running, this only works if you restart the applet (which might not be the best idea).

---

Use "Java-to-Javascript Communication". There is a certain document introducing the JSObject -class. It can be found here . There is also the "Common DOM API" which can be used to access the DOM-structure of the HTML-page. It sounds like what you're searching for, but it seems a little outdated.

Als, this seems to be no standard (just like the <applet> -tag) and therefor, some browsers might not or not completely implement support for that. You'll have to try it out.

Answer 2

// provide a JS function to return the value of textbox
// call it to get the value..
String userInput = JOptionPane.showInputDialog(this, value, ..