java调用js里面的某一个方法

ScriptEngineManager mgr = new ScriptEngineManager();  
ScriptEngine engine = mgr.getEngineByName("JavaScript"); 
//加载一个文件 
try {
File f=new File("d:/wang.js");

Reader r=null;
r = new InputStreamReader(new FileInputStream(f));
 
 //把Reader放入eval中(读者可以去API看一下,重载了很多的eval()方法)  
 engine.eval(r);         
 Invocable inv = (Invocable) engine;        
 String value = (String)inv.invokeFunction("test");   
 System.out.println(value);   

} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ScriptException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}