java-caller

4.0.0 • Public • Published

Java Caller for Node.js

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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 20
  • 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} = 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 node 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

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 });

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

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Install

npm i java-caller

Weekly Downloads

11,703

Version

4.0.0

License

MIT

Unpacked Size

35.9 kB

Total Files

6

Last publish

Collaborators

  • nvuillam