Many of the situation we need to interact with the other programs. Here is a small demo on how to invoke or execute the jar.
In Node js, the “child_process” is the module which will do the needful. Through chlid_process, we can execute OS command.
Here have used one java program which takes input from the command line and prints the value which is in command line execution.
Java Program
Below is the java program we have used.
public class DemoCall {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(args[0]);
}
}
We will create an executable jar (invoke-jar) from this program. We will invoke that jar from the command line.
java -jar invoke-jar "Jar is invoked by Node js"
if you want to know about how to create the executable jar, please click here.
Node.js Program
We have created “child_process” object and call exec() function to pass command line parameters to execute the jar. When the process will run, it will invoke the jar and output will be printed on the console. We have a file called “executejar.js”.Below is the code,
const exec = require('child_process').exec;
const childPorcess = exec('java -jar C:\\Users\\devil\\eclipse-workspace\\invoke-jar.jar "Jar is invoked by Node js"', function(err, stdout, stderr) {
if (err) {
console.log(err)
}
console.log(stdout)
})
you can observe that callback function has three arguments like err, stdout, stderr.
err-> To handle the node js error, stdout -> To store the output from the java program, stderr-> It is for handling the java error.
Another js program named index.js, which contains
var exec=require('./executejar')
Command for execution,
node index
Output:
Jar is invoked by Node.js
You can get the whole code from the Github repo. Below is the link:
https://github.com/sahajahanAlli/invoke-jar-using-node-js
- Navigate to the folder(queue-example) using command prompt/windows powershell
- Type command “npm install”. It will install node modules.
- Type command “npm start”. It will show the output.
Please feel free to comments or provide the suggestion.
2 comments
when i call a jar file then it gives this error
“Command failed: java -jar e:\Hello.jar
‘java’ is not recognized as an internal or external command,
operable program or batch file.
”
my node js file is
//—————————————————————–
router.get(‘/readFingerPrint’,function(req,res){
try
{
var filePath = path.join(__dirname,’../References/Hello.jar’);
var testFilePath = ‘e:\\Hello.jar’
readFingerPrint.exec(‘java -jar e:\\Hello.jar’, function(err, stdout, stderr) {
if (err) {
console.log(err)
res.status(500).send(err);
}
else if(stderr)
{
console.log(err)
res.status(500).send(err);
}
else
{
var i=stdout;
console.log(i+i);
res.json({result:(i+i)});
}
})
}
catch(err)
{
res.status(500).send(err);
}
});
//—————————————————
and Hello.jar is here
public class Hello {
public static void main(String[] args) {
// Prints “Hello, World” in the terminal window.
System.out.println(“Hello”);
}
}
Thanks Vikash..
I have checked your program. It is working fine for me. Output is {“result”:”Hello\r\nHello\r\n”}.
I think java path isn’t set in your system. Could you please check ? is “java” command in your system working fine or n’t?
ifn’t , please set the java path. then try again. you can follow the instruction in the link https://java.com/en/download/help/path.xml
Below is your program I have used
var express = require(‘express’);
var router = express.Router();
const readFingerPrint = require(‘child_process’)
router.get(‘/readFingerPrint’, function(req, res) {
try {
readFingerPrint.exec(‘java -jar ./Hello.jar’, function(err, stdout, stderr) {
if (err) {
console.log(err)
res.status(500).send(err);
} else if (stderr) {
console.log(err)
res.status(500).send(err);
} else {
var i = stdout;
console.log(i + i);
res.json({ result: (i + i) });
}
})
} catch (err) {
res.status(500).send(err);
}
});
module.exports = router;
java :-
public class Hello {
public static void main(String[] args) {
// Prints “Hello, World” in the terminal window.
System.out.println(“Hello”);
}
}
Please let us know if you face any issue.