Hi,
I have a batch file which sets the java runtime path before running my program. I have multiple versions of JRE installed( the same is possible in client as well). I need to find the latest JRE version from a Windows system and set that in classpath in the batch file.
Any inputs on how to do this?
Thanks,
Sujie
you can list all the installed JVMs using a registry reader program like the following:
import java.util.Iterator;
import ca.beq.util.win32.registry.RegistryKey;
import ca.beq.util.win32.registry.RegistryValue;
import ca.beq.util.win32.registry.RootKey;
public class RegistryReader {
private static final String INSTALLED_JVM_REG = "SOFTWARE\\JavaSoft\\Java Runtime Environment";
public static void main(String[] args) {
RegistryKey r = new RegistryKey(RootKey.HKEY_LOCAL_MACHINE, INSTALLED_JVM_REG);
//Get Current Version
RegistryValue v = r.getValue("CurrentVersion");
//System.out.println(v.toString());
if (r.hasSubkeys()) {
Iterator i = r.subkeys();
while (i.hasNext()) {
r = (RegistryKey) i.next();
//System.out.println(x.toString());
System.out.println(r.getValue("JavaHome").toString().substring(16));//16 = "JavaHome:REG_SZ:".length();
} // while
} // if
}
}
To run this program, you'll need a reg utility from http://www.bayequities.com/tech/Products/jreg_key.shtml. Basically you'll need jRegistryKey.jar and jRegistryKey.dll.
You should then compare the values JavaHomes and find the latest JVM.
@echo off
::Find the current (most recent) Java version
start /w regedit /e reg1.txt "HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment"
type reg1.txt | find "CurrentVersion" > reg2.txt
if errorlevel 1 goto ERROR
for /f "tokens=2 delims==" %%x in (reg2.txt) do set JavaTemp=%%~x
if errorlevel 1 goto ERROR
echo Java Version = %JavaTemp%
del reg1.txt
del reg2.txt
::Get the home directory of the most recent Java
start /w regedit /e reg1.txt "HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\%JavaTemp%"
type reg1.txt | find "JavaHome" > reg2.txt
if errorlevel 1 goto ERROR
for /f "tokens=2 delims==" %%x in (reg2.txt) do set JavaTemp=%%~x
if errorlevel 1 goto ERROR
echo Java home path (per registry) = %JavaTemp%
del reg1.txt
del reg2.txt
