JSNI (call from javascript to java)

Question

In the JSNI example to call a Java method from Javascript, they write this:

$wnd.testJSNI = @com.jsni.client.HelloJSNI::testJSNI(Ljava/lang/String;)(test);

I tried to figure it out, but couldn't find what exactly is meant by Ljava/lang/String? Am I required to pass these arguments?

Jason Hall · Accepted Answer · 2012-03-19 15:48:26Z

3

The Ljava/lang/String; tells GWT that the method expects a String parameter, which will be passed in as the test value in your sample code.

In general in JSNI methods you need to tell GWT what the parameter types are, or you can use the shortcut (*) which tells GWT to figure it out for itself. This works in most cases as far as I've seen. So your code could also be written as:

var test = 'This is my test string';
$wnd.testJSNI = @com.jsni.client.HelloJSNI::testJSNI(*)(test);

answered Mar 19, 2012 at 15:48

Jason Hall

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CodeChimp · Accepted Answer · 2012-03-19 15:52:15Z

-1

That 'Ljava/lang/String;" format looks like JNI. It's used to describe, in text, a data type. You can read more here.

answered Mar 19, 2012 at 15:52

CodeChimp

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3 Comments

Jason Terk Over a year ago

It's not JNI, it's JSNI which is GWT specific.

CodeChimp Over a year ago

I understand, but that format is from JNI, which is dealing with cross-language data types. I am guessing they are re-using the same nomenclature for JSNI, which is doing the same thing (calling code from one language from another language), and needs to know what data type you are sending.

Eliran Malka Over a year ago

agreed, JNI is used under the hood, and those types are being declared this way for the JVM. +1.

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