Java Caller for Node.js

Lightweight cross-platform javascript module to easily call java commands from Node.js sources.

• Automatically installs required Java version if not present on the system
• Compliant with JDK & JRE from 8 to 21
• Uses node spawn method to perform the call

There are two ways to use java-caller:

• module: Manually call JavaCaller in your custom JS/TS code (example project)
• CLI: Just define a java-caller-config.json and you can deliver your java executables as your own NPM packages ! (example project, which can be used as starter kit)

Installation

npm install java-caller --save

Usage

const JavaCaller = require('java-caller');
const java = new JavaCaller(JAVA_CALLER_OPTIONS);
const {status, stdout, stderr} = await java.run(JAVA_ARGUMENTS,JAVA_CALLER_RUN_OPTIONS);

JAVA_CALLER_OPTIONS

Parameter	Description	Default value	Example
jar	Path to executable jar file		"myfolder/myjar.jar"
classPath	If jar parameter is not set, classpath to use Use : as separator (it will be converted if runned on Windows), or use a string array.	. (current folder)	"java/myJar.jar:java/myOtherJar.jar"
useAbsoluteClassPaths	Set to true if classpaths should not be based on the rootPath	false	true
mainClass	If classPath set, main class to call		"com.example.MyClass"
rootPath	If classPath elements are not relative to the current folder, you can define a root path. You may use __dirname if you classes / jars are in your module folder	. (current folder)	"/home/my/folder/containing/jars"
minimumJavaVersion	Minimum java version to be used to call java command. If the java version found on machine is lower, java-caller will try to install and use the appropriate one	8	11
maximumJavaVersion	Maximum java version to be used to call java command. If the java version found on machine is upper, java-caller will try to install and use the appropriate one Can be equal to minimumJavaVersion		10
javaType	jre or jdk (if not defined and installation is required, jre will be installed)		"jre"
additionalJavaArgs	Additional parameters for JVM that will be added in every JavaCaller instance runs		["-Xms256m","-Xmx2048m"]
javaExecutable	You can force to use a defined java executable, instead of letting java-caller find/install one. Can also be defined with env var JAVA_CALLER_JAVA_EXECUTABLE		"/home/some-java-version/bin/java.exe"

JAVA_ARGUMENTS

The list of arguments can contain both arguments types together:

• Java arguments (-X*, -D*). ex: "-Xms256m", "-Xmx2048m"
• Main class arguments (sent to public static void main method). ex: "--someflag" , "--someflagwithvalue myVal" , "-c"

Example: ["-Xms256m", "--someflagwithvalue myVal", "-c"]

JAVA_CALLER_RUN_OPTIONS

Parameter	Description	Default	Example
detached	If set to true, node will not wait for the java command to be completed. In that case, childJavaProcess property will be returned, but stdout and stderr may be empty, except if an error is triggered at command execution	false	true
stdoutEncoding	Adds control on spawn process stdout	utf8	ucs2
waitForErrorMs	If detached is true, number of milliseconds to wait to detect an error before exiting JavaCaller run	500	2000
cwd	You can override cwd of spawn called by JavaCaller runner	process.cwd()	some/other/cwd/folder
javaArgs	List of arguments for JVM only, not the JAR or the class	[]	['--add-opens=java.base/java.lang=ALL-UNNAMED']
windowsVerbatimArguments	No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to true automatically when shell is specified and is CMD.	true	false
windowless	If windowless is true, JavaCaller calls javaw instead of java to not create any windows, useful when using detached on Windows. Ignored on Unix.	false	true
windowsHide	On Windows, hide the subprocess console window that would normally be created. Set to false if you need Java UI dialogs to be visible (e.g., print dialogs). Ignored on Unix.	true	false
timeout	In milliseconds the maximum amount of time the process is allowed to run.	undefined	1000
killSignal	The signal value to be used when the spawned process will be killed by timeout or abort signal.	SIGTERM	SIGINT

Examples

Call a class located in classpath

const java = new JavaCaller({
    classPath: 'test/java/dist',
    mainClass: 'com.nvuillam.javacaller.JavaCallerTester'
});
const { status, stdout, stderr } = await java.run();

Call a class with multiple folders in the classPath

const java = new JavaCaller({
    classPath: ['C:\\pathA\\test\\java\\dist', 'C:\\pathB\\test\\java\\dist'],
    mainClass: 'com.nvuillam.javacaller.JavaCallerTester'
});
const { status, stdout, stderr } = await java.run();

Call a class located in classpath with java and custom arguments

const java = new JavaCaller({
    classPath: 'test/java/dist',
    mainClass: 'com.nvuillam.javacaller.JavaCallerTester'
});
const { status, stdout, stderr } = await java.run(['-Xms256m', '-Xmx2048m', '--customarg nico']);

Call a class in jar located in classpath

const java = new JavaCaller({
    classPath: 'test/java/jar/JavaCallerTester.jar',
    mainClass: 'com.nvuillam.javacaller.JavaCallerTester'
});
const { status, stdout, stderr } = await java.run();

Call a runnable jar

const java = new JavaCaller({
    jar: 'test/java/jar/JavaCallerTesterRunnable.jar',
});
const { status, stdout, stderr } = await java.run();

Call a detached java process

const java = new JavaCaller({
    classPath: 'test/java/dist',
    mainClass: 'com.nvuillam.javacaller.JavaCallerTester'
});
const { status, stdout, stderr, childJavaProcess } = await java.run(['--sleep'], { detached: true });

// Kill later the java process if necessary
childJavaProcess.kill('SIGINT');

Call a windowless java process

const java = new JavaCaller({
    classPath: 'test/java/dist',
    mainClass: 'com.nvuillam.javacaller.JavaCallerTester'
});
const { status, stdout, stderr } = await java.run(['--sleep'], { windowless: true });

Call java process with visible windows (e.g., for print dialogs)

const java = new JavaCaller({
    classPath: 'test/java/dist',
    mainClass: 'com.nvuillam.javacaller.JavaCallerTester'
});
// Set windowsHide to false to allow Java UI dialogs to be visible
const { status, stdout, stderr } = await java.run([], { windowsHide: false });

When using CLI mode with --no-windows-hide flag:

node index.js --no-windows-hide

You can see more examples in test methods

TROUBLESHOOTING

Set environment variable DEBUG=java-caller before calling your code using java-caller module, and you will see the java commands executed.

Example debug log:

java-caller Found Java version 1.80131 +1s
java-caller Java command: java -Xms256m -Xmx2048m -cp C:\Work\gitPerso\node-java-caller\test\java\dist com.nvuillam.javacaller.JavaCallerTester -customarg nico +1ms

CONTRIBUTE

Contributions are very welcome !

Please follow Contribution instructions

RELEASE NOTES

See complete CHANGELOG