Check the ram of a jvm process using nashron (given only a jre)

check_ram.js

function addUrlToClasspath(pathName) {
    var/*java.net.URLClassLoader*/
        sysloader = /*(java.net.URLClassLoader) */ java.lang.ClassLoader.getSystemClassLoader();
    var/*java.lang.Class*/ sysclass = java.net.URLClassLoader.class;
    var ClassArray = Java.type("java.lang.Class[]");
    var parameters = new ClassArray(1);
    parameters[0] = java.net.URL.class;
    var/*java.lang.reflect.Method*/ method = sysclass.getDeclaredMethod("addURL", parameters);
    method.setAccessible(true);
    var ObjectArray = Java.type("java.lang.Object[]");
    var array = new ObjectArray(1);
    var/*java.io.File*/ f = new java.io.File(pathName);
    if (f.isFile()) {
        var/*java.net.URL*/ u = f.toURL();
        array[0] = u;
        //if(u.toString().endsWith(".jar"))
        method.invoke(sysloader, array);
    } else {
        var/*File[]*/ listOfFiles = f.listFiles();
        if (listOfFiles != null)
            for (var i = 0; i < listOfFiles.length; i++) {
                if (listOfFiles[i].isFile()) {
                    var/*java.net.URL*/ u = listOfFiles[i].toURL();
                    array[0] = u;
                    method.invoke(sysloader, array);
                }
            }
    }
}

function addToLibPath(path) {
    var/*java.io.File*/ f = new java.io.File(path);
    path = f.getAbsolutePath();

    if (!f.exists()) {
        throw new Error("THe lib " + path + " doesn't exists")
    }

    if (java.lang.System.getProperty("java.library.path") != null) {
        // If java.library.path is not empty, we will prepend our path
        // Note that path.separator is ; on Windows and : on Unix-like,
        // so we can't hard code it.
        var newLibraryPath = path
            + java.lang.System.getProperty("path.separator")
            + java.lang.System.getProperty("java.library.path")
        print("To set", newLibraryPath)
        java.lang.System.setProperty("java.library.path", newLibraryPath);
    } else {
        java.lang.System.setProperty("java.library.path", path);
    }

    // Important: java.library.path is cached
    // We will be using reflection to clear the cache
    var ClassLoader = Java.type("java.lang.ClassLoader")
    var fieldSysPath = ClassLoader.class.getDeclaredField("sys_paths");
    fieldSysPath.setAccessible(true);
    fieldSysPath.set(null, null);
}


addUrlToClasspath("./tools.jar");
addToLibPath(".")

print("JAVA_LIBRARY_PATH", java.lang.System.getProperty("java.library.path"));

var AttachProvider = Java.type("com.sun.tools.attach.spi.AttachProvider")
var list = Java.type("com.sun.tools.attach.VirtualMachine").list()
var managementAgentJar = "/usr/local/openjdk-8/lib/management-agent.jar"

var attachProvider = AttachProvider.providers().get(0);

var descriptor = null;
var processString = "my-jar.jar"

Array.prototype.forEach.call(list, function(desc) {
    if(desc.displayName().indexOf(processString) >= 0) descriptor = desc
})

print(list)
print("Using", descriptor)

if (descriptor == null)
    throw new Error("not found");

var virtualMachine = attachProvider.attachVirtualMachine(descriptor);
// virtualMachine.loadAgent(managementAgentJar, "com.sun.management.jmxremote");

var portObject = virtualMachine.getAgentProperties().get("com.sun.management.jmxremote.localConnectorAddress");

var target = new javax.management.remote.JMXServiceURL(portObject + "");
var connector = javax.management.remote.JMXConnectorFactory.connect(target);
var remote = connector.getMBeanServerConnection();

var c = remote.getMBeanCount();

print("MBeanCount: " + c);


var composite = remote.getAttribute(new javax.management.ObjectName("java.lang:type=Memory"), "HeapMemoryUsage");


print("Commited", composite.get("committed"));
print("Init", composite.get("init"));
print("MAX", composite.get("max"));
print("USED", composite.get("used"));