locate-java-home

Locates JAVA_HOME on any platform, and can differentiate between different versions.

Usage

npm install @viperproject/locate-java-home

import LocateJavaHome from '@viperproject/locate-java-home'; // or var LocateJavaHome = require('@viperproject/locate-java-home').default;
LocateJavaHome(function(error, javaHomes) {
   javaHomes.forEach(function(homeInfo) {
      console.log("Found Java " + homeInfo.version + " at " + homeInfo.path);
      if (homeInfo.isJDK) {
        console.log("It's a JDK!");
      }
   });
});

// Limit to JDKs for Java 6 and above.
LocateJavaHome({
    // Uses semver :) Note that Java 6 = Java 1.6, Java 8 = Java 1.8, etc.
    version: ">=1.6",
    mustBeJDK: true
}, function(error, javaHomes) {
    // Done.
});

Motivation

I originally wrote this utility for DoppioJVM, which requires access to the Java 8 JDK during build time.

I required the following:

• The ability to check the version of java in JAVA_HOME.
• Verify that JAVA_HOME is a JDK and not a JRE.
• Detect a Java 8 JDK even if it is not the default version of Java installed.
• Have the above work across Windows, Mac, and Linux.

Since this functionality is likely generally useful, I have decided to release this as a standalone library! Enjoy! :)

API

The locate-java-home package is a single async function that takes an optional options argument:

LocateJavaHome(options, function(error, javaHomes) {});
LocateJavaHome(function(error, javaHomes) {});

javaHomes is an array of objects that contain information about each JAVA_HOME we found:

{
  // Absolute path to JAVA_HOME
  path: string;
  // Version of Java in the JAVA_HOME.
  version: string;
  // Security number of this version of Java.
  // Typically, you want a version with the largest security number.
  // Note: For Java 9 and later, this will always be '0' as this is now
  // encoded into the version number. See http://openjdk.java.net/jeps/223
  // and https://blogs.oracle.com/java-platform-group/a-new-jdk-9-version-string-scheme
  security: number;
  // True if this JAVA_HOME is a JDK, false if it is a JRE.
  isJDK: boolean;
  // Is this version of Java 64-bit?
  is64Bit: boolean;
  // Paths to various executables.
  executables: {
    java: string;
    // JDK only:
    javac: string;
    javap: string;
  }
}

Options

locate-java-home surfaces a number of useful options:

{
  // Semantic versioning string (e.g. ~1.6, >1.6....)
  version: string;
  // Are you specifically looking for a JDK over a JRE?
  mustBeJDK: boolean;
  // Are you specifically looking for a JRE over a JDK?
  mustBeJRE: boolean;
  // Are you specifically looking for a 64-bit JAVA_HOME?
  mustBe64Bit: boolean;
  // Do you want locate-java-home to exit fatally if one of the found JAVA_HOME
  // locations does not function appropriately? (Mainly useful for debugging.)
  paranoid: boolean;
}

Global Script

If you install locate-java-home globally, you'll have access to the locate-java-home command line tool. Currently, it lists all of the JAVA_HOME locations on your system. If there's any desire to expand it into a full-fledged command line tool that exposes the options of this library, let me know!