Nashorn JavaScript Engine in Java with Examples
Last Updated :
06 Apr, 2023
Nashorn: Nashorn is a JavaScript engine which is introduced in JDK 8. With the help of Nashorn, we can execute JavaScript code at Java Virtual Machine. Nashorn is introduced in JDK 8 to replace existing JavaScript engine i.e. Rhino. Nashorn is far better than Rhino in term of performance. The uses of invoking dynamic feature, conversion of JavaScript code into the bytecode directly into the memory etc makes the Nashorn more famous in JDK 8. We can execute JavaScript code by using the command-line tool and by embedding the JavaScript code into Java source code.
Executing JavaScript code by using console: For Nashorn engine, Java 8 introduced one new command-line tool i.e.jjs. We have to follow the below steps to execute JavaScript code through the console:
Executing JavaScript file by embedding JavaScript file into Java code: We can execute JavaScript file by embedding JavaScript file into Java code with the help of ScriptEngine class. ScriptEngine class is introduced in JDK 6. By the help of the ScriptEngine class, we can create a JavaScript engine and with the JavaScript engine, we can execute the javaScript file.
Example 1:
import javax.script.*;
import java.io.*;
public class Geeksforgeeks {
public static void main(String[] args)
throws Exception
{
ScriptEngine ee = new ScriptEngineManager()
.getEngineByName( "Nashorn" );
ee.eval( new FileReader( "geeks.js" ));
}
}
|
Output:
Welcome to Geeksforgeeks!!!
Example 2:
import javax.script.*;
import java.io.*;
public class Geeksforgeeks {
public static void main(String[] args)
throws Exception
{
ScriptEngine ee = new ScriptEngineManager()
.getEngineByName( "Nashorn" );
ee.eval( "print('Welcome to Geeksforgeeks!!!"
+ " Executing JavaScript code with the"
+ " help of Nashorn engine');" );
}
}
|
Output:
Welcome to Geeksforgeeks!!! Executing JavaScript code with the help of Nashorn engine
Apart from above, with the help of Nashorn JavaScript Engine, we can perform multiple operations like:
- Providing JavaScript variable from Java Code: Suppose we have one JavaScript file name with geeks.js and geeks.js requires one variable during execution. With the help of Nashorn, we can pass the variable to JavaScript file from java code.
Example 1: geeks.js file, which needs name variable to get executed
print( "Welcome to Geeksforgeeks!!! Mr. " +name);
|
Example 2: Java code providing name variable to the JS file
import javax.script.*;
import java.io.*;
public class Geeksforgeeks {
public static void main(String[] args)
throws Exception
{
ScriptEngine ee
= new ScriptEngineManager()
.getEngineByName( "Nashorn" );
Bindings bind
= ee.getBindings(
ScriptContext.ENGINE_SCOPE);
bind.put( "name" , "Bishal Kumar Dubey" );
ee.eval( new FileReader( "geeks.js" ));
}
}
|
Output:
Welcome to Geeksforgeeks!!! Mr. Bishal Kumar Dubey
- Calling JavaScript function from Java code: We can call JavaScript function from Java code with the help of Nashorn. Suppose we create one file name with geeks.js and the file contains two functions like below:
var func1 = function (){
print( "Simple JavaScript function!!!" );
}
var func2 = function (reader){
print( "Hello " +reader);
}
|
import javax.script.*;
import java.io.*;
public class Geeksforgeeks {
public static void main(String[] args)
throws Exception
{
ScriptEngine ee
= new ScriptEngineManager()
.getEngineByName( "Nashorn" );
ee.eval( new FileReader( "geeks.js" ));
Invocable invocable = (Invocable)ee;
invocable.invokeFunction( "func1" );
invocable.invokeFunction( "func2" ,
"Bishal Kumar Dubey" );
}
}
|
Output:
Simple JavaScript function!!!
Hello Bishal Kumar Dubey
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