Develop Reference

Executing a new JavaFX application on a separate JVM

I'm trying to launch a new process on a separate JVM via code following the method illustrated here:
Executing a Java application in a separate process
The code I'm using is the following (taken from the question above):
public static int exec(Class klass) throws IOException, InterruptedException {
String javaHome = System.getProperty("java.home");
String javaBin = javaHome +
File.separator + "bin" +
File.separator + "java";
String classpath = System.getProperty("java.class.path");
String className = klass.getName();
ProcessBuilder builder = new ProcessBuilder(javaBin,"-cp",classpath,className);
Process process = builder.inheritIO().start();
process.waitFor();
return process.exitValue();
}
...in which klass is the class I want to launch.
This would work for a normal Java process, but the problem is that I'm trying to launch a JavaFX application, and the code above generates the following error:
Error: JavaFX runtime components are missing, and are required to run this application
So, to add the JavaFX modules, I tried including the --module-path and --add-modules commands in the declaration of builder, I even attempted copying and pasting the entire execution command, and I kept getting this other error:
Unrecognized option: (command string with modules)
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
How could I solve this?
Let me know if details are needed.

Since the advent of modules, there are at least three different ways a JavaFX application can be configured:
Put everything on the module-path, including the JavaFX modules and your module.
This is the ideal situation but not always possible/viable (e.g. because of incompatible dependencies).
Put the JavaFX modules on the module-path and your own code on the class-path.
This configuration requires the use of --add-modules.
Put everything on the class-path, including the JavaFX modules and your own code.
With this configuration your main class cannot be a subtype of Application. Otherwise you get the error you mentioned in your question: "Error: JavaFX runtime components are missing, and are required to run this application".
This configuration allows for easy use of so-called fat/uber JARs.
Warning: This approach is explicitly unsupported.
The command line used with ProcessBuilder will depend on which configuration your application uses. You also have to take into account any other options passed the command line, such as the default encoding or locale. Unfortunately, your question doesn't provide enough information to tell what exactly is going wrong. The error you mention makes me think you're using the third configuration, but I can't be sure.
That said, I'll give some examples of launching the same application from within the application; you should be able to modify things to fit your needs. Note I used Java/JavaFX 13.0.1 when testing the below code.
Configuration #1
Put everything on the module-path.
module-info.java:
module app {
requires javafx.controls;
exports com.example.app to
javafx.graphics;
}
Main.java:
package com.example.app;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Path;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import static java.lang.System.getProperty;
public class Main extends Application {
private static void launchProcess() {
try {
new ProcessBuilder(
Path.of(getProperty("java.home"), "bin", "java").toString(),
"--module-path",
getProperty("jdk.module.path"),
"--module",
getProperty("jdk.module.main") + "/" + getProperty("jdk.module.main.class"))
.inheritIO()
.start();
} catch (IOException ex) {
throw new UncheckedIOException(ex);
}
}
#Override
public void start(Stage primaryStage) {
Button launchBtn = new Button("Launch process");
launchBtn.setOnAction(
event -> {
event.consume();
launchProcess();
});
primaryStage.setScene(new Scene(new StackPane(launchBtn), 500, 300));
primaryStage.setTitle("Multi-Process Example");
primaryStage.show();
}
}
Command line:
java --module-path <PATH> --module app/com.example.app.Main
Replace "<PATH>" with a path containing both the JavaFX modules and the above module.
Configuration #2
Put JavaFX modules on the module-path and your code on the class-path.
Main.java:
package com.example.app;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Path;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import static java.lang.System.getProperty;
public class Main extends Application {
private static void launchProcess() {
try {
new ProcessBuilder(
Path.of(getProperty("java.home"), "bin", "java").toString(),
"--module-path",
getProperty("jdk.module.path"),
"--add-modules",
"javafx.controls",
"--class-path",
getProperty("java.class.path"),
Main.class.getName())
.inheritIO()
.start();
} catch (IOException ex) {
throw new UncheckedIOException(ex);
}
}
#Override
public void start(Stage primaryStage) {
Button launchBtn = new Button("Launch process");
launchBtn.setOnAction(
event -> {
event.consume();
launchProcess();
});
primaryStage.setScene(new Scene(new StackPane(launchBtn), 500, 300));
primaryStage.setTitle("Multi-Process Example");
primaryStage.show();
}
}
Command line:
java --module-path <M_PATH> --add-modules javafx.controls --class-path <C_PATH> com.example.app.Main
Replace "<M_PATH>" with a path containing the JavaFX modules and replace "<C_PATH>" with a path containing the above code.
Configuration #3
Put everything on the class-path. Note the main class (now Launcher) is not a subclass of Application.
Launcher.java:
package com.example.app;
import javafx.application.Application;
public class Launcher {
public static void main(String[] args) {
Application.launch(Main.class, args);
}
}
Main.java:
package com.example.app;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Path;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import static java.lang.System.getProperty;
public class Main extends Application {
private static void launchProcess() {
try {
new ProcessBuilder(
Path.of(getProperty("java.home"), "bin", "java").toString(),
"--class-path",
getProperty("java.class.path"),
Launcher.class.getName())
.inheritIO()
.start();
} catch (IOException ex) {
throw new UncheckedIOException(ex);
}
}
#Override
public void start(Stage primaryStage) {
Button launchBtn = new Button("Launch process");
launchBtn.setOnAction(
event -> {
event.consume();
launchProcess();
});
primaryStage.setScene(new Scene(new StackPane(launchBtn), 500, 300));
primaryStage.setTitle("Multi-Process Example");
primaryStage.show();
}
}
Command line:
java --class-path <PATH> com.example.app.Launcher
Replace "<PATH>" with a path containing the JavaFX JARs and the above code.

opening chrome in selenium issue

I'm currently taking my first automated test class and the instructor has us creating a program in Eclipse after loading Selenium and create a step in the program to look at an executable to bring up chrome then designate a website to check. It looks like i am stuck in a loop?
Here is the program:
java program
Here is the result:
program result
any and all help would be appreciated. Thank you for your time.

I think this is what you want
This code is to open the default browser and go to a specific link
You can specify the path of any browser you want from the path in the code
import java.awt.Desktop;
import java.net.URI;
public class openBrowser {
public openBrowser() {
try {
if (Desktop.isDesktopSupported() && Desktop.getDesktop().isSupported(Desktop.Action.BROWSE)) {
Desktop.getDesktop().browse(new URI("https://www.google.com"));
}
}catch (Exception e) {
// TODO: handle exception
}
}
public static void main(String[]args) {
new openBrowser();
}
}
For your code you can follow the following steps
Download ChromeDriver from here
Extract the zip file and follow the path ( because it is easy ) C:\\chromeDriver\\chromedriver.exe
include the ChromeDriver location in your PATH environment variable
Download the required Libraries from the following junit openqa
Add the Libraries to your project ( Build Path )
then this is your code
import java.util.logging.Level;
import java.util.logging.Logger;
import org.openqa.selenium.*;
import org.openqa.selenium.chrome.*;
import org.junit.Test;
public class WebDriverDemo {
#Test
public static void main(String[] args) {
System.setProperty("webdriver.chrome.driver", "C:\\chromeDriver\\chromedriver.exe");
WebDriver driver = new ChromeDriver();
driver.get("https://www.google.com/");
WebElement searchBox = driver.findElement(By.name("q"));
searchBox.sendKeys("ChromeDriver");
searchBox.submit();
try {
Thread.sleep(10000);
} catch (InterruptedException ex) {
Logger.getLogger(WebDriverDemo.class.getName()).log(Level.SEVERE, null, ex);
}
driver.quit();
}
}
During the implementation of the code in the eclipse, many problems occurred, so I advise you to implement the project on NetBeans
I use Java 8 and Windows 8.1

Nashorn java.lang.NoClassDefFoundError: jdk/nashorn/api/scripting/JSObject

I am migrating my Eclipse RCP to use JDK 8 and I heavily use the JS ScriptEngine. Now that Nashorn is introduced I had to add the following line to get the importClass and importPackage functions to work:
load("nashorn:mozilla_compat.js");
After doing so, I got java.lang.NoClassDefFoundError: jdk/nashorn/api/scripting/JSObject.
I am using Nashorn inside an Eclipse RCP. The problem occurs when I call a Java function from the Javascript and try to use the parameter sent. The parameter I want to send is a Javascript function that I would like to execute call on later in the code.
I have the following code:
TestNashorn.java
package com.test.nashorn;
import java.io.FileNotFoundException;
import java.io.FileReader;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.Invocable;
import jdk.nashorn.api.scripting.JSObject;
public class TestNashorn {
public static void main(String[] args) {
ScriptEngine engine = (new ScriptEngineManager()).getEngineByName("js");
try {
engine.eval(new FileReader("C:/Users/user/workspace_nashorn/TestNashorn/src/com/test/nashorn/test.js"));
Object o = ((Invocable)engine).invokeFunction("generate");
} catch (ScriptException | FileNotFoundException | NoSuchMethodException e) {
e.printStackTrace();
}
}
public static int test(JSObject o1) {
System.out.println(o1.getClass().toString());
JSObject som = ((JSObject)o1);
return 1;
}
}
test.js
load("nashorn:mozilla_compat.js");
importClass(com.test.nashorn.TestNashorn);
function generate()
{
function asd(variablex) { print('Hello, ' + variablex); }
var result = TestNashorn.test(asd);
}
The problem occurs in line JSObject som = ((JSObject)o1);, although I can successfully import jdk.nashorn.api.scripting.JSObject;.
The exception message exactly says:
jdk.nashorn.api.scripting.JSObject cannot be found by com.test.nashorn_1.0.0.qualifier

So.. I got to fix my issue and was able to use JSObject in my code. What I have done was the following:
Added -Dorg.osgi.framework.bundle.parent=ext to myproduct.product file
This added it to the .ini file in my product build which revealed the classes found in Nashorn APIs.

Doing an action after a set delay in java

Edit: Got it to work. My problem was I was using cmd to compile which exited the vm before the delay ended. Switched to jGrasp and the program worked as intended. Next I need to learn how to actually make a java applet to properly run on my computer. Thanks for your help everyone
I'm trying to set an alarm of sorts using java. I'd like to open a webpage after a set delay. The code below compiles and runs without errors or warnings but running the code does nothing. Just starts and stops the program. I have a feeling the issue arises from how I catch the exceptions but I'm not sure. I also am a little lost on what the actionPerformed() method does. Any help or insight is greatly appreciated
import java.awt.Desktop;
import java.net.URI;
import java.net.URISyntaxException;
import java.io.IOException;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.Timer;
public class YtAlarmTest
{
public static void main (String [] args)
{
String url = "https://stackoverflow.com/questions/ask";
int delay = 1000;
ActionListener task = new ActionListener()
{
public void actionPerformed(ActionEvent evt)
{
try
{
if (Desktop.isDesktopSupported())
{
Desktop.getDesktop().browse(new URI(url));
}
}
catch (URISyntaxException e)
{
System.out.println("exception");
}
catch (IOException e)
{
System.out.println("exceptio");
}
}
};
new Timer(delay, task).start();
}
}

How to run the Linux "cd" command from Java?

I want to write a Java program to delete ~12 directories or files which are under my home directory. I am able to do this by using
Process proc = Runtime.getRuntime().exec("rm -rf *path*")
But I have to run this command 12 times or I can keep it in loop. What I really want is to have a file in my home directory that contains the names of all the directories and files to delete in it. My Java program should go to the home directory, read the file, and delete all the specified files.
I am stuck at the very first step – I am not able to cd to the home directory. Please let me know how can I achieve this.
Thanks for all of your replies.
But, here I don't really want to use the Java util classes rather I want to learn a way using which I can run Linux commands in my Java class. Being a deployment Intern, I have to reset the environment every time before deploying a new environment for the customer. For this, I repeatedly use some basic Linux commands. I can write a shell script to do this but for this time, I want to write a Java class in which I can put all these Linux commands and run from one class.
The commands which I use are:
kill all java processes which are started by the admin ONLY – for this I need to use multiple Linux commands with “pipe”
Remove all 12-directories/files from home directory
stop some services (like siebel, etc.) – for this I need to go under the particular directories and run ./shutdown.sh or ./stop_ns, etc.
run some database scripts – to reset the database schemas
again start the services – same as step 2 except this time I need to run ./start_ns, etc.
I really appreciate if you can let me know
a. How can I navigate into a directory using Java code
b. How can I run multiple Linux commands using pipe using Java code

Why do you need to "go" to the home directory? Just read the file wherever you are:
String homeDirectory = System.getProperty("user.home");
File file = new File(homeDirectory, "filenames.txt"); // Or whatever
// Now load the file using "file" in the constructor call to FileInputStream etc
It's very rarely a good idea to require that a process changes working directory just to do the right thing.

You dont need to change directory. You can just read file using absolute path using FileReader(String fileName).

For deleting entire directories, try Apache Commons IO's class FileUtils:
FileUtils.deleteDirectory(new File(System.getProperty("user.home")));
Or use cleanDirectory to delete everything in home but not home itself:
FileUtils.cleanDirectory(new File(System.getProperty("user.home")));
If you want to delete specific files only (e.g. those matching a name pattern), list the files first, then delete them:
File startDir = new File(System.getProperty("user.home"));
//this should return the leaf files first, then the inner nodes of the directory tree
Collection<File> files = FileUtils.listFiles(startDir , someFileFiler, someDirFilter);
for(File f : files) {
f.delete();
}

"cd" is a shell internal command, not a executable program.
Even you can change dir in java program by whatever means like JNA, when it exit, the current dir in shell is not changed, because the java program runs in another process than the shell.
But we still can do something about it.
eg. I want to make a new shell command called xcd, it popup a GUI shows a list let you select directories existed in bash history, and change current dir to it for you.
in ~/.bashrc add a line:
xcd(){
XCDRES=`xcd.sh`
if [ "$XCDRES" ]; then
cd "$XCDRES"
fi
}
2.xcd.sh is
#!/bin/bash
java -cp $PATH1/xcd.jar neoe.xcd.Main
and add xcd.sh to PATH
the java program is
package neoe.xcd;
import java.awt.Toolkit;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import javax.swing.JComponent;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
public class Main {
public static String getUserHomeDir() {
return System.getProperty("user.home");
}
public static void main(String[] args) throws Exception {
new Main().run();
}
public static String readString(InputStream ins, String enc) throws IOException {
if (enc == null)
enc = "UTF-8";
BufferedReader in = new BufferedReader(new InputStreamReader(ins, enc));
char[] buf = new char[1000];
int len;
StringBuffer sb = new StringBuffer();
while ((len = in.read(buf)) > 0) {
sb.append(buf, 0, len);
}
in.close();
return sb.toString();
}
private String[] selection = new String[1];
private void run() throws Exception {
File hisfile = new File(getUserHomeDir(), ".bash_history");
if (!hisfile.exists()) {
System.err.println(".bash_history not exists, quit");
return;
}
String[] ss = readString(new FileInputStream(hisfile), null).split("\n");
List<String> res = new ArrayList<String>();
Set uniq = new HashSet();
for (String s : ss) {
s = s.trim();
if (!s.startsWith("cd /")) {
continue;
}
s = s.substring(3);
File f = new File(s);
if (f.isDirectory()) {
s = f.getAbsolutePath();
if (uniq.contains(s)) {
continue;
}
uniq.add(s);
res.add(s);
}
}
if (res.isEmpty()) {
System.err.println("no cd entry, quit");
return;
}
Collections.sort(res);
String cd1 = selectFromList(res);
if (cd1 == null) {
System.err.println("not selected, quit");
return;
}
doCd(cd1);
}
private void doCd(String cd1) throws Exception {
System.out.println(cd1);
}
private String selectFromList(List<String> res) {
final JList list = new JList(res.toArray());
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
final JDialog frame = wrapFrame(new JScrollPane(list), "select dir to cd");
list.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
if (e.getClickCount() > 1) {
String s = (String) list.getSelectedValue();
selection[0] = s;
frame.dispose();
}
}
});
list.addKeyListener(new KeyAdapter() {
#Override
public void keyPressed(KeyEvent e) {
int kc = e.getKeyCode();
if (kc == KeyEvent.VK_ESCAPE) {
frame.dispose();
} else if (kc == KeyEvent.VK_ENTER) {
String s = (String) list.getSelectedValue();
selection[0] = s;
frame.dispose();
}
}
});
frame.setVisible(true);
frame.requestFocus();
return selection[0];
}
private JDialog wrapFrame(JComponent comp, String title) {
JDialog frame = new JDialog();
frame.setTitle("select dir to cd");
frame.setModal(true);
frame.add(comp);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setSize(400, 600);
frame.setLocationRelativeTo(null);
return frame;
}
}
use xcd in shell.

You can't really do that. Java programs don't really allow you to change the "current working directory" as most people understand it (not without using native code, anyway). The normal Java approach is to open a File instance on the directory you want to manipulate, and then use operations on that instance to manipulate the files/directories in question.
For details on how to delete directories programatically in Java, see: Delete directories recursively in Java