calling javaScript from java method

Question

I want to execute JavaScript function from Java. I used the following piece of code

ScriptEngineManager manager = new ScriptEngineManager();    
ScriptEngine engine = manager.getEngineByName("JavaScript"); 

but this throws an exception for the alert() method ?

engine.eval("alert('HI');");

Answer 1

So. I'm pretty sure your code here is incorrect.

engine.eval("alert(HI);");

Try.

engine.eval("alert('Hi');");

unless you have a variable HI declared.

Answer 2

you can not call javascript from java in any way. javascript is client side language and executed on browser where as java is executed on server

Update :- Thanks guys i learnt something new here.

when i execute the code in op i get below error

Error executing script: ReferenceError: "alert" is not defined in <eval> at line number 1

Reason is alert is not part of JavaScript, it's part of the window object provided by web browsers.so, Nashhorn javascript engine does not know about it.

Please see ReferenceError: "alert" is not defined

Answer 3

It appears that "alert()" is part of the window object provided by web browsers. it doesn't exist here

I have modified java code:

ScriptEngineManager manager = new ScriptEngineManager();      
ScriptEngine engine  = manager.getEngineByName("JavaScript");
engine.eval("print('HI');");

This is useful: Java Scripting Programmer's Guide
Information about javscript window object: The Window Object

Answer 4

您做错了方法，您无法从Java代码调用JavaScript函数，因为一个在客户端执行，而另一个在服务器端执行...即使您使用某种API来实现，这也是错误的代码结构方式。