Develop Reference

Run Glassfish on Java 7 with Java 8 installed on Windows box

I am working on a legacy project with Glassfish 3 and Java 7. The problem is in order to run Eclipse, I need Java 8. When I install Java 8, I can no longer run Glassfish under Java 7 for some reason.
I do see the two JDKs in control panel for User tab in Java Runtime Environment Settings, but under System once I install Java 8, I only see Java 8 there. So it just runs under Java 8 from what I can tell.
This is my first week of Java.

Simply specify the needed JDK for your Glassfish domain:
Find this configuration file: C:\servers\glassfish\config\asenv.bat (this path is an example)
Edit the file, comment the previous JDK and add the wanted one:
REM set AS_JAVA=C:\Program Files\Java\jdk1.8\..
set AS_JAVA=C:\Program Files\Java\jdk1.7\..

When you install a new JVM, usually it sets itself as the default version on that platform which is the first one found on the Path environment variable. In order to find what version is the default one, run this command: java -version and the output will be something like:
openjdk version "1.8.0_111"
OpenJDK Runtime Environment (build 1.8.0_111-8u111-b14-2ubuntu0.16.10.2-b14)
OpenJDK 64-Bit Server VM (build 25.111-b14, mixed mode)
As you see in this case the default one is OpenJDK-8.
If you want to change that, you have to do some changes which depend on the platform can vary but usually you should:
Change JAVA_HOME environment variable to point to desired JVM
installation path
Add desired JVM <installation-path>/bin to Path environment variable and remove other JVM paths.
(Detailed example for Windows, Example for Ubuntu)
Notice that, this potentially could affect every program that uses Java and does not explicitly reference a specific version of Java in its config.
But If you want the default version to remain intact and only make an exception for some programs you have to do it in their config/settings.
For Example for Eclipse you can modify eclipse.ini file and specify the JVM it uses by adding this line (more info):
-vm
/opt/oracle-jdk-1.8.0/bin/java
or for Windows:
-vm
C:\Java\JDK\1.8\bin\javaw.exe
there is a similar config for glassfish too. You can choose which JVM should be the default version and which the one exceptional programs gonna use, In your case I recommend that keep version 7 as default and change eclipse config to use version 8.

Java -version prints a wrong version

I have multiple versions of Java installed in the environment(I know it is bad). I've set the JAVA_HOME to jdk 1_4 directory. This is not installed, but extracted from zip and placed it somewhere. We have java 1.8 JRE also installed in the system. I never set the path to this installed directory. Now i'm trying to run some ant script that depends on jdk 1_4. I get some exception saying that it is not able to find tools.jar in java1.8... .
My question is that when the path and java_home are set to jdk 14 why does the ant look for 1.8 version of java? I'm confused.
Update: I have looked up the duplicate issue.
Additional details: Java -version prints 1.8 with jdk 14 in the path and java_home. I uninstalled 1.8. reopened cmd tried java -version, now it errors out saying that it is not able to find java1.8 instead of trying to find the next java available in the path or java_home.
Error shown:
C:\Users\usrpao>java
Error: could not open `C:\Program Files\Java\jre8\lib\amd64\jvm.cfg'

I have multiple versions of Java installed in the environment(I know it is bad). I've set the JAVA_HOME to jdk 1_4 directory.
Not wrong at all. I have a similar setup because I have to switch between Java version.
First, install Java JDKs in the root of your drive. No spaces in the directory names. For example, C:\Java\Java-1.6-21 and C:\Java\Java-1.7-5.
In your Environment Variables section in your System Control Panel (under Advance), create an environment variable to point to each one of these Java Home directories. For example, JAVA_HOME_17 = C:\Java\Java-1.7.5 and JAVA_HOME_16 = C:\Java\Java-1.6-21. This should be a System Environment variable.
Create a JAVA_HOME environment variable that points to the Java version you want: JAVA_HOME = %JAVA_HOME_17%.
Now in the System PATH, prefix the PATH (the very first entry) with %JAVA_HOME%\bin.
When you open a console window, your default java and javac commands will be the correct Java version.
If you need to change a version, change the JAVA_HOME environment variable to point to the correct environment variable and open a new console window. Now that new Java will be in your path.
NOTE: It is vitally important that %JAVA_HOME%\bin is in the first part of your PATH before C:\Windows\System32. You don't want the java.exe that exists in that directory to be your default java.

You haven't specified the operating system, so:
on windows, java installs a java.exe in C:\Windows\system32, which is probably on the path before java_home, and so gets picked up
on Linux, various distributions that support multiple installed java versions will also have some symlink earlier on the path. Run 'which java' to determine where that symlink is

Multiple java versions in the system is the problem, I uninstalled all the java versions first. Restarted my machine. Path and java home points to the jdk 1.4. java -version now points to the version specified in the path. Thanks all.

Import a propertie file in QSH Command - iseries

is there a way, that i could load a propertie file in a QSH Command.
The Problem is my System is running on a Java 1.4 Version and my Programm is only running in a Java 1.6 Version. So i wrote a propertie files that says, take the 1.6 version but i absulutly have no plan how to implemnt it in my code..
java -cp "Test.jar:lib/*" my.package.MainClass
The name of the Properie file is Java_Version.properties
Do you have any solution ?
regards

You can specify a properties file to load with the environment variable QIBM_JAVA_PROPERTIES_FILE.
QIBM_JAVA_PROPERTIES_FILE=/path/to/myproperties.properties java -cp "Test.jar:lib/*" my.package.MainClass
In addition properties in a file named SystemDefault.properties will be automatically loaded if it exists in the user home directory.
Here are some links to additional documentation that may be useful:
Installing Java on your IBM i server
Support for multiple Java Development Kits (JDKs)
Java system properties
SystemDefault.properties

Use the environment variable JAVA_HOME On IBM i 7.1, I would specify:
JAVA_HOME='/QOpenSys/QIBM/ProdData/JavaVM/jdk60/64bit'
export JAVA_HOME
java -version
IBM Support Document N1011999 Support Java Versions by Operating System Release describes the JAVA_HOME settings for various operating system releases.

Java default version doesnt reflect after PATH change

I am running currently on Java 1.7.0_17 64bit version and I want to launch an app using Java 32 bit version.
I updated PATH variable to point to (C:\Program Files (x86)\Java\jre7\bin) Java 32 bit version. Then did a java -version it still shows the 64bit version.
I gave up and tried to do a java -d32 -jar abc.jar and then it gives me an
java -d32
Error: This Java instance does not support a 32-bit JVM.
Please install the desired version.
Please let me know how can the system refresh the latest Java settings done in the PATH variable.

There is probably a java.exe in your C:\WINDOWS\System32\ folder leftover from the previous installation. Replace it with the one in C:\Program Files (x86)\Java\jre7\bin.

What is JAVA_HOME? How does the JVM find the javac path stored in JAVA_HOME?

I would like to know what JAVA_HOME is. Where do I set the path of javac.exe and java.exe. It is in environment variables? When I compile a Java program from command prompt, how does the JVM find javac.exe?

JVM does not find java.exe. It doesn't even call it. java.exe is called by the operating system (Windows in this case).
JAVA_HOME is just a convention, usually used by Tomcat, other Java EE app servers and build tools such as Gradle to find where Java lives.
The important thing from your point of view is that the Java /bin directory be on your PATH so Windows can find the .exe tools that ship with the JDK: javac.exe, java.exe, jar.exe, etc.

JAVA_HOME and JRE_HOME are not used by Java itself. Some third-party programs (for example Apache Tomcat) expect one of these environment variables to be set to the installation directory of the JDK or JRE. If you are not using software that requires them, you do not need to set JAVA_HOME and JRE_HOME.
PATH is an environment variable used by the operating system (Windows, Mac OS X, Linux) where it will look for native executable programs to run. You should add the bin subdirectory of your JDK installation directory to the PATH, so that you can use the javac and java commands and other JDK tools in a command prompt window. Courtesy: coderanch

set environment variable
JAVA_HOME=C:\Program Files\Java\jdk1.6.0_24
classpath=C:\Program Files\Java\jdk1.6.0_24\lib\tools.jar
path=C:\Program Files\Java\jdk1.6.0_24\bin

The command prompt wouldn't use JAVA_HOME to find javac.exe, it would use PATH.

JAVA_HOME is a environment variable (in Unix terminologies), or a PATH variable (in Windows terminology). A lot of well behaving Java applications (which need the JDK/JRE) to run, looks up the JAVA_HOME variable for the location where the Java compiler/interpreter may be found.

JAVA HOME is used for setting up the environment variable for JAVA. It means that you are providing a path for compiling a JAVA program and also running the same. So, if you do not set the JAVA HOME( PATH ) and try to run a java or any dependent program in the command prompt.
You will deal with an error as
javac : not recognized as internal or external command.
Now to set this, Just open your Java jdk then open bin folder then copy the PATH of that bin folder.
Now, go to My computer right click on it----> select properties-----> select Advanced system settings----->Click on Environment Variables------>select New----->give a name in the text box Variable Name and then paste the path in Value.
That's All!!

JAVA_HOME is an environment variable which is read by some development tools like Apache Tomcat, Apache Maven, Gradle, Jenkins etc. Usually, JAVA_HOME is set to point to JDK instead of JRE because these development tools need to use tools like compiler, debugger, document generator etc. which are only available in JDK since JDK is a development kit. JRE is only meant for running java applications. JDK = JRE + Development tools
Consumer facing Java applications don't read JAVA_HOME variable and they just need to know where the JVM is located and that's why JVM location (directory) needs to be added to the PATH variable. This is automatically done for you when you install Java software. Whenever you try to run a Java application by either double clicking on the app or through command line, your operating system reads PATH variable to locate and run JVM and it doesn't look for JAVA_HOME variable.

use this command /usr/libexec/java_home to check the JAVA_HOME

JAVA_HOME is an Environment Variable set to the location of the Java directory on your computer.
PATH is an internal DOS command that finds the /bin directory of the version of Java that you are using. Usually they are the same, except that the PATH entry ends with /bin

Basically JAVA_HOME is use to set path of the java . it is use in windows. it's used for set path of the multiple software like as java EE , ANT and Maven.
this is the steps to solve your problem:
only for core java to set path :
path :"C:\Program Files\Java\jre1.8.0_77\bin"
but when you are use multi built like as ANT , core java then you are used JAVE_HOME in environment .
follow the steps :
JAVA_HOME:"C:\Program Files\Java\jre1.8.0_77\bin"
ANT_HOME:"C:\ant\apache-ant-1.9.6"
Path: JAVA_HOME, ANT_HOME;
it is the systematic way to set the environment variable..