I have a jar file that runs fine from the Windows 10 command line, but is not working on my desktop Ubuntu 18.04 command line. The file was exported from Eclipse as a jar, and copied to Ubuntu. The project has about 30 classes over a half dozen packages. I've done some renaming in order to simplify things for this question.
This is the command used to run the jar:
java -jar myproject.jar
On Ubuntu, I get the error "Could not find or load main class com.a.b.LaunchThis"
Following are some of the things I've tried, based on suggestions from many similar posts. Sorry if this is a duplicate, but I couldn't find a workable answer.
I verified that the current Java is 1.8 using the commands:
$ update-alternatives --config java
and
$ java -version
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-8u252-b09-1~18.04-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)
(I also verified that the program runs using java 8 on Windows.)
I ran the following check, which displays all the files, and confirmed that com/a/b/LaunchThis.class exists and is spelled exactly the same way.
java tj myproject.jar
The manifest seems correct.
Manifest-Version: 1.0
Main-Class: com.a.b.LaunchThis
I also tried unpacking the jar and running the program directly from the folder /myproject which contains both /com and META-INF. That should work, shouldn't it?
java com.a.b.LaunchThis
java com/a/b/LaunchThis
java com.a.b/LaunchThis
And from one level outside the myproject folder:
java myproject/com/a/b/LaunchThis
java myproject.com.a.b/LaunchThis
java myproject.com.a.b.LaunchThis
java myproject/com.a.b.LaunchThis
I am not totally clear on when the syntax requires . or /. The package command in "LaunchThis" which holds the main entry point is the following:
package com.a.b;
And in each of the above iterations I also tried including "-cp myproject.jar" as an option.
Always the exact same error message.
To be careful about not having a typo in the above, I first ran the ls command to make sure the file could be found (then edited this line to create the variants).
ls myproject.com.a.b.LaunchThis.class
Any suggestions as to what else to try?
For grins, running with Java11 gets this response:
Error: Could not find or load main class com.a.b.LaunchThis
Caused by: java.lang.NoClassDefFoundError: javafx/event/EventHandler
This makes some sense, because Java11 does not include JavaFX. But Java 8 does include EventHandler. It's been a part of Java since JavaFX 2.
UPDATE: I made two "Hello world" jars, one with and one without JavaFX on an Ubuntu installation of Eclipse running OpenJDK 8. To get the version with JavaFX to run, I downloaded the Oracle JDK 1.8, and linked to /lib/etc/jfxrt.jar as an "external jar" library. Both programs run in Eclipse but only the non-FX jar works. The FX jar gives exactly the same error message.
I think this pretty much establishes my problem to be one of not having JavaFX as part of OpenJDK 8.
My plan is to now try out two solutions: (1) copying the Oracle jfxrt.jar into the OpenJDK lib, (2) backloading OpenJFX 8.
Simply installing OpenJFX from repository loads OpenJFX 11, which is a little dated but will work with the OpenJDK 11.
The issue here is that the repository OpenJDK 8 on Ubuntu 18.04 does not include JavaFX. I'm guessing that the error message results from the fact that a JavaFX main() is located on a class that extends the JavaFX class Application.
How to fix this?
There are a number of things I tested.
First, one could use Oracle's JDK 1.8 instead. I ruled this out due to licensing issues.
Some sites suggested copying the jfxrt.jar from either the Oracle JDK 1.8 or from a working Java program that uses JavaFX and uses a self-contained JRE. I found that if I linked to the Oracle jfxrt.jar (located in the /jre/lib/ext folder) as an external jar, I could run a simple, "Hello world" javafx program in Eclipse. But I could not run the program after it was exported to a jar.
One answer on a related stackoverflow thread suggested copying over several additional files along with jfxrt.jar, which I tried. This did not work, so I'm not going to pass that on.
The solution that has been most successful came from a link provided in the comment by #dave_thomson_085, How do I get Java FX running with OpenJDK 8 on Ubuntu 18.04.2 LTS?.
This answer involves purging and reinstalling openjfx with an older version, and marking it to NOT be subjected to updates.
The code provided by Wolfgang Fahl (which he credits to Druidefix) follows:
apt purge openjfx
apt install openjfx=8u161-b12-1ubuntu2 libopenjfx-jni=8u161-b12-1ubuntu2 libopenjfx-java=8u161-b12-1ubuntu2
apt-mark hold openjfx libopenjfx-jni libopenjfx-java
Now, I can run and test jars containing Java8 using JavaFX that were built on my Windows Eclipse, on my Ubuntu desktop.
I do get a warning message which I haven't dealt with yet:
Gtk-Message: 13:25:40.829: Failed to load module "canberra-gtk-module"
But this is not preventing my programs from running.
I imagine some Java gurus with experience delivering Java apps on Windows desktops will be able to ace this one. I've always been a Mac/Linux Java developer so this is uncharted territory for me :-/.
I have to write a Java 8 Swing application and install it on a Windows 10 (64-bit) machine. My gameplan is to package the app as an executable JAR and wrap it with Launch4J, so that it looks like a native Windows EXE (.exe file). However its a little bit more complication than that when it comes to the distribution:
There will be the JAR/EXE as mentioned above, lets call it myapp.exe (built from myapp.jar)
The app will output logs to a (local?) directory, myapp.log
The app will load a config file at runtime, myapp.properties
The distribution should also contain the User's Guide, MyApp User Guide.html
Let's assume a Java 8 JRE/JDK is already installed on the machine, so we don't need to worry about installing Java itself.
The installation process must be simple and include:
Removing the old version (and all of its other artifacts such as the log file, config/properties file, user guide, etc) off the machine completely
Installing the new version at either the Windows 10 default location, or allowing the user to specify a different location
Additionally, if at all possible, I'd like the installation process to include:
A requirements check for things like minimum memory and disk space, OS version info/compatibility (i.e. make sure its being installed on Windows 10, etc.)
Provide an easy-to-use wizard such as an MSI that the user can click though
Optionally install shortcuts to the user's Desktop
Given all this, I'm wondering what my options are in the modern Windows 10/Java/Launch4J landscape. Are there tools that will help me script together MSIs quickly, or do I have to write my own in, say, C#/.NET and have that be a separate binary/project? If MSIs aren't an option, what options exist that might hit all my bullets above?
I realize I could just distribute the whole thing as a ZIP, and have the installation process look something like:
Save the ZIP to some place on the user's machine, say, the Desktop
Move the previous app and its artifacts to the trash, manually
Unzip the new ZIP
However that feels janky and I'm looking for something more professional. Any solutions here?
JDK 8 is bundled with a tool called javapackager (formerly javafxpackager) which is part of JavaFX. However, you can use it package java swing application without using JavaFX. This tool can generate an installer file (exe or msi) which contains the application and the Java runtime as well.
Here is an example:
javapackager -deploy -native exe -Bruntime="C:\Program Files\Java\jdk1.8.0_66\jre" -Bicon=app_icon.ico -BsystemWide=true -BshortcutHint=true -outdir packages -outfile appFile -srcdir dist -srcfiles MyApp.jar;COPYING.txt -appclass somePackage.MainClass -BlicenseFile=COPYING.txt -name appName -title "The application name"
For more information, see adding icon to bundle using javapackager
There is also a new tool called jpackage which is based on javapackager. It is proposed to be released with the next JDK release, JDK 14. Note that javapackager was removed from JDK since version 11 as part of the removal of JavaFX.
See A Brief Example Using the Early Access jpackage Utility
Tools: Some deployment tools information:
Multi-Platform Installers
List of the major MSI installer tools
WiX quick start tips (the open source, free tool with a heavy learning curve)
"Hello WiX - step-by-step in Visual Studio"
"Hello World" - WiX style
Advanced Installer: As stated in a comment above you can use Advanced Installer to install Java applications on Windows and Mac (no Linux support).
Videos: Here are some videos from Advanced Installer (commercial tool) on Java installations:
Hello Java Installer: 1 minute video that shows the basics of installing a Java application
List of Java-related videos: https://www.youtube.com/user/AdvancedInstaller/search?query=java+jre
Tutorial (to read): Package your Java application for Windows and for Mac OS. Java landing page.
Digression: Not Java as such - do have a skim. Auto-updating applications using various deployment technologies: What is the best practice to auto upgrade MSI based application?
Links:
Make Installer of java Application
Installer for Java Web Application
How to create windows installer
How to create a MSI Windows installer for a Java program?
Old: How can I convert my Java program to an .exe file?
I have developed a program using Java SE on Windows 7.
I build this app and it runs well on Windows.
I tried to run on Linux, so it runs but after some steps of:
Removing OpenJDK app.
Install Java JDK from terminal
Run jar file from terminal.
I need to make an installer on Windows - Linux - Mac, which installs JDK package and make the program run by double clicking.
Try using JarSplice. It is a nifty tool for converting Jar files into runnables for different systems. There are lots of tutorials on the internet on how to use it, although it is very well labelled and I found it simple enough to use.
I am trying to run the MARS simulator in order to do some Assembly homework in Ubutnu 11.04. MARS(jar file) requires Java to be installed and so I did install Java.
After that I typed
java -jar .jar
and as a result I got:
Failed to load Main-Class manifest attribute from .jar
What must I do in order to run this file properly?
There are different Java implementations and you are not using the "official" one. (As is clear from the libgcj.so that appears on your error) and that one tends to be the most reliable.
Ubuntu 11.04 might still have the java-6-sun package (it was deprecated on newer Ubuntu releases because of license conflicts), so you should try with that one.
If that java is not in Ubuntu, then you can try downloading and installing Java from the Oracle site.
We have a couple of applications running on Java 5 and would like now to bring in an application based on Java 6. Can both java versions live together under Windows?
Is there any control panel to set the appropriate Java version for different applications, or any other way to set up, what version of Java will be used to run that particular application?
Of course you can use multiple versions of Java under Windows. And different applications can use different Java versions. How is your application started? Usually you will have a batch file where there is something like
java ...
This will search the Java executable using the PATH variable. So if Java 5 is first on the PATH, you will have problems running a Java 6 application. You should then modify the batch file to use a certain Java version e.g. by defining a environment variable JAVA6HOME with the value C:\java\java6 (if Java 6 is installed in this directory) and change the batch file calling
%JAVA6HOME%\bin\java ...
I was appalled at the clumsiness of the CLASSPATH, JAVA_HOME, and PATH ideas, in Windows, to keep track of Java files. I got here, because of multiple JREs, and how to content with it. Without regurgitating information, from a guy much more clever than me, I would rather point to to his article on this issue, which for me, resolves it perfectly.
Article by: Ted Neward: Multiple Java Homes: Giving Java Apps Their Own JRE
With the exponential growth of Java as a server-side development language has come an equivablent
exponential growth in Java development tools, environments, frameworks, and extensions.
Unfortunately, not all of these tools play nicely together under the same Java VM installation. Some
require a Servlet 2.1-compliant environment, some require 2.2. Some only run under JDK 1.2 or above,
some under JDK 1.1 (and no higher). Some require the "com.sun.swing" packages from pre-Swing 1.0
days, others require the "javax.swing" package names.
Worse yet, this problem can be found even within the corporate enterprise, as systems developed using
Java from just six months ago may suddenly "not work" due to the installation of some Java Extension
required by a new (seemingly unrelated) application release. This can complicate deployment of Java
applications across the corporation, and lead customers to wonder precisely why, five years after the
start of the infamous "Installing-this-app-breaks-my-system" woes began with Microsoft's DLL schemes,
we still haven't progressed much beyond that. (In fact, the new .NET initiative actually seeks to solve the
infamous "DLL-Hell" problem just described.)
This paper describes how to configure a Java installation such that a given application receives its own,
private, JRE, allowing multiple Java environments to coexist without driving customers (or system
administrators) insane...
It is absolutely possible to install side-by-side several JRE/JDK versions. Moreover, you don't have to do anything special for that to happen, as Sun is creating a different folder for each (under Program Files).
There is no control panel to check which JRE works for each application. Basically, the JRE that will work would be the first in your PATH environment variable. You can change that, or the JAVA_HOME variable, or create specific cmd/bat files to launch the applications you desire, each with a different JRE in path.
We can install multiple versions of Java Development kits on the same machine using SDKMan.
Some points about SDKMan are as following:
SDKMan is free to use and it is developed by the open source community.
SDKMan is written in bash and it only requires curl and zip/unzip programs to be present on your system.
SDKMan can install around 29 Software Development Kits for the JVM such as Java, Groovy, Scala, Kotlin and Ceylon. Ant, Gradle, Grails, Maven, SBT, Spark, Spring Boot, Vert.x.
We do not need to worry about setting the _HOME and PATH environment variables because SDKMan handles it automatically.
SDKMan can run on any UNIX based platforms such as Mac OSX, Linux, Cygwin, Solaris and FreeBSD and we can install it using following commands:
$ curl -s "https://get.sdkman.io" | bash
$ source "$HOME/.sdkman/bin/sdkman-init.sh"
Because SDKMan is written in bash and only requires curl and zip/unzip to be present on your system. You can install SDKMan on windows as well either by first installing Cygwin or Git Bash for Windows environment and then running above commands.
Command sdk list java will give us a list of java versions which we can install using SDKMan.
Installing Java 8
$ sdk install java 8.0.201-oracle
Installing Java 9
$ sdk install java 9.0.4-open
Installing Java 11
$ sdk install java 11.0.2-open
Uninstalling a Java version
In case you want to uninstall any JDK version e.g., 11.0.2-open you can do that as follows:
$ sdk uninstall java 11.0.2-open
Switching current Java version
If you want to activate one version of JDK for all terminals and applications, you can use the command
sdk default java <your-java_version>
Above commands will also update the PATH and JAVA_HOME variables automatically. You can read more on my article How to Install Multiple Versions of Java on the Same Machine.
It should be possible changing setting the JAVA_HOME environment variable differently for specific applications.
When starting from the command line or from a batch script you can use set JAVA_HOME=C:\...\j2dskXXX to change the JAVA_HOME environment.
It is possible that you also need to change the PATH environment variable to use the correct java binary. To do this you can use set PATH=%JAVA_HOME%\bin;%PATH%.
I use a simple script when starting JMeter with my own java version
setlocal
set JAVA_HOME="c:\java8"
set PATH=%JAVA_HOME%\bin;%PATH%;
java -version
To have a java "portable"
you can use this method here:
https://www.whitebyte.info/programming/java/how-to-install-a-portable-jdk-in-windows-without-admin-rights
Or use links. While it is rather unpleasant to update the PATH in a running environment, it's easy to recreate a link to a new version of JRE/JDK. So:
install different versions of JDK you want to use
create a link to that folder either by junction or by built-in mklink command
set the PATH to the link
If other version of java is to be used, delete the link, create a new one, PATH/JAVA_HOME/hardcoded scripts remain untouched
Invoking Java with "java -version:1.5", etc. should run with the correct version of Java. (Obviously replace 1.5 with the version you want.)
If Java is properly installed on Windows there are paths to the vm for each version stored in the registry which it uses so you don't need to mess about with environment versions on Windows.
If you use Java Web Start (you can start applications from any URL, even the local file system) it will take care of finding the right version for your application.
Using Java Web Start, you can install multiple JRE, then call what you need.
On win, you can make a .bat file:
1- online version:
<your_JRE_version\bin\javaws.exe> -localfile -J-Djnlp.application.href=<the url of .jnlp file.jnlp> -localfile -J "<path_temp_jnlp_file_.jnlp>"
2- launch from cache:
<your_JRE_version\bin\javaws.exe> -localfile -J "<path_of_your_local_jnlp_file.jnlp>"