Nitin Agrawal
Contact -
  • Home
  • Interviews
    • Secret Receipe
    • InterviewFacts
    • Resume Thoughts
    • Daily Coding Problems
    • BigShyft
    • Companies
    • Interviews Theory
  • Programming Languages
    • Java Script >
      • Tutorials
      • Code Snippets
    • Reactive Programming >
      • Code Snippets
    • R
    • DataStructures >
      • LeetCode Problems >
        • Problem10
        • Problem300
      • AnagramsSet
    • Core Java >
      • Codility
      • Program Arguments OR VM arguments & Environment variables
      • Java Releases >
        • Java8 >
          • Performance
          • NasHorn
          • WordCount
          • Thoughts
        • Java9 >
          • ServiceLoaders
          • Lambdas
          • List Of Objects
          • Code Snippets
        • Java14 >
          • Teeing
          • Pattern
          • Semaphores
        • Java17 >
          • Switches
          • FunctionalStreams
          • Predicate
          • Consumer_Supplier
          • Collectors in Java
        • Java21 >
          • Un-named Class
          • Virtual Threads
          • Structured Concurrency
      • Threading >
        • ThreadsOrder
        • ProducerConsumer
        • Finalizer
        • RaceCondition
        • Executors
        • Future Or CompletableFuture
      • Important Points
      • Immutability
      • Dictionary
      • Sample Code Part 1 >
        • PatternLength
        • Serialization >
          • Kryo2
          • JAXB/XSD
          • XStream
        • MongoDB
        • Strings >
          • Reverse the String
          • Reverse the String in n/2 complexity
          • StringEditor
          • Reversing String
          • String Puzzle
          • Knuth Morris Pratt
          • Unique characters
          • Top N most occurring characters
          • Longest Common Subsequence
          • Longest Common Substring
        • New methods in Collections
        • MethodReferences
        • Complex Objects Comparator >
          • Performance
        • NIO >
          • NIO 2nd Sample
        • Date Converter
        • Minimum cost path
        • Find File
      • URL Validator
    • Julia
    • Python >
      • Decorators
      • String Formatting
      • Generators_Threads
      • JustLikeThat
    • Go >
      • Tutorial
      • CodeSnippet
      • Go Routine_Channel
      • Suggestions
    • Methodologies & Design Patterns >
      • Design Principles
      • Design Patterns >
        • TemplatePattern
        • Adapter Design Pattern
        • Proxy
        • Lazy Initialization
        • CombinatorPattern
        • Singleton >
          • Singletons
        • Strategy
  • Frameworks
    • Apache Velocity
    • React Library >
      • Tutorial
    • Spring >
      • Spring Boot >
        • CustomProperties
        • ExceptionHandling
        • Custom Beans
        • Issues
      • Quick View
    • Rest WebServices >
      • Interviews
      • Swagger
    • Cloudera BigData >
      • Ques_Ans
      • Hive
      • Apache Spark >
        • ApacheSpark Installation
        • SparkCode
        • Sample1
        • DataFrames
        • RDDs
        • SparkStreaming
        • SparkFiles
    • Integration >
      • Apache Camel
    • Testing Frameworks >
      • JUnit >
        • JUnit Runners
      • EasyMock
      • Mockito >
        • Page 2
      • TestNG
    • Blockchain >
      • Ethereum Smart Contract
      • Blockchain Java Example
    • Microservices >
      • Messaging Formats
      • Design Patterns
    • AWS >
      • Honeycode
    • Dockers >
      • GitBash
      • Issues
      • Kubernetes
  • Databases
    • MySql
    • Oracle >
      • Interview1
      • SQL Queries
    • Elastic Search
  • Random issues
    • TOAD issue
    • Architect's suggestions
  • Your Views

Nashorn

5/29/2014

0 Comments

 
Java 8 is out for past 2 months & I was just going through its new feature Nashorn which is a javascript engine bringing Java & JavaScript more closer so that we can use the features of Java in JavaScript easily, cool haan.

So I just got my hands dirty in this Nashorn a bit & below are the files which I used to check its features. Before you execute these files you need java8, Eclipse Luna is supporting Java8 but I used Netbeans 8 to check the new features.

package nashorn;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
//import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import jdk.nashorn.api.scripting.ScriptObjectMirror;

/**
 *
 * @author Nitin
 */
public class Nas {
    public static void main(String... args) throws ScriptException, NoSuchMethodException{
//        Below we need to create one Nashorn engine to access the methods in JS
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
        try {
//          Below we are giving the name & path to the JS which we want to access using the given engine
            engine.eval(new FileReader("D:\\Eclipse Workspaces\\Java8\\src\\nashorn\\Dummy.js"));
        } catch (ScriptException ex) {
            Logger.getLogger(Nas.class.getName()).log(Level.SEVERE, null, ex);
        } catch (FileNotFoundException ex) {
            Logger.getLogger(Nas.class.getName()).log(Level.SEVERE, null, ex);
        }

//      Above created engine must be made Invocable to use it
Invocable invocable = (Invocable) engine;

// Calling the JS method fun2 & passing it the required input parameter
Object result = invocable.invokeFunction("fun2", new Date());
System.out.println(result);
System.out.println(result.getClass());

ArrayList al = new ArrayList();
al.add(1);
al.add(2);
invocable.invokeFunction("iter", al);
    }
   
//    Methods to be called from JS must be public & if using the class name to access these then such methods must be static also
    public static void fun3(ScriptObjectMirror mirror) {
    String[] itr = mirror.getOwnKeys(true);
    System.out.println(mirror.getClassName() + ": " +
        Arrays.toString(mirror.getOwnKeys(true)));
     for(int i = 0; i < itr.length; i++){
        System.out.println(itr[i] + " : " + mirror.get(itr[i]));
    }
}
   
    public static void fun2(Object object) {
    System.out.println(object.getClass());
}
   
    public static void fun4(ScriptObjectMirror person) {
    System.out.println("Full Name is: " + person.callMember("getFullName"));
}
//    Below method is called from JS using the instance of Nas class
    public void instanceMethod(){
        System.out.println("In the instance method");
    }
}




/*
 * @author Nitin
 */

// It is used to get the class type of the given Java Class
var Nas = Java.type('nashorn.Nas');

// Normal JS function having one reference to call this function
var fun1 = function(name) {
    print('Hi there from Javascript, ' + name);
    return "greetings from javascript";
};

var fun2 = function (object) {
    print("JS Class Definition: " + Object.prototype.toString.call(object));
    return object.class;
};

// method must be public & static
Nas.fun2(new Number(23));

//instantiating using the above obtained class type
var inNas = new Nas();
// Only those methods can be called which are public using the object of the class
inNas.instanceMethod();
//below will error - has no such function "instanceMethod"
// because the instanceMethod is associated with instance & not the class, normal Java rule
//Nas.instanceMethod();

// passing the whole object to the Java method
Nas.fun3({
    nitin: 'agrawal',
    agrawal: 'nitin'
});

// creation of the Person type class in JS
function Person(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
    print("Hi in Person")
    this.getFullName = function() {
        return this.firstName + " " + this.lastName;
    }
    }
//    instantiating the above class & passing that object to the Java class
    var person1 = new Person("Nitin", "Agrawal");
    Nas.fun4(person1);

// used to import Java classes in JS
    var imports = new JavaImporter(java.io, java.lang);
   
// object is passed from Java code & accessed in JS here & also uses the String methods as this pkg is imported above.
// So we can also import other pkg, means multiple pkgs can be imported.
var iter = function(object){
    print("Direct Access : " + object.toString().valueOf()[4]);
    var List = Java.type(object.class.toString().substring(6));
    var cList = new List();
    cList = object;
    print("Through type casting JS : " + cList.get(0));
}

// below is the use of Thread class & Runnable interface from Java
var Runnable = Java.type('java.lang.Runnable');
var Printer = Java.extend(Runnable, {
    run: function() {
        print(this + 'printed from a separate thread');
    }
});

var Thread = Java.type('java.lang.Thread');
new Thread(new Printer()).start();
new Thread(function() {
    print(this + 'printed from another thread');
}).start();

// below the instance of Date type from Java is created in JS
var Date = Java.type('java.util.Date');
var date = new Date();
date.year += 1900;
print(date.year);  // 2014


// below shows that how we can bind the properties of two variables in JS
var o1 = {};
var o2 = { nitin: 'agrawal'};
Object.bindProperties(o1, o2);
print(o1.nitin);    // agrawal
o1.foo = 'NIT';
print(o2.foo);    // NIT

// below shows that if we are having multiple imports & we want to use some specific imported class as there can be same named class from other imported
// pkgs, then we can use the specific class like shown below.
with (imports) {
 var str = new String("Nitin84");
 System.out.println(str.substring(0, 5));
}

0 Comments



Leave a Reply.

    Author

    Nitin Agrawal

    Archives

    May 2014

Powered by Create your own unique website with customizable templates.