Why doesn't the Java SDK installer set JAVA_HOME?

Question

I always wondered why I have to manually set the JAVA_HOME environment variable after installing the Java SDK.

JAVA_HOME=c:\\Program Files\\Java\\jdk1

Answer 1

The vcvarsall.bat mechanism is a convenient way for Visual C++ to provide a console with the correct variables without messing with the user's/system's environment variables. However, it assumes that Installshield is the only way to get code onto the system. The JDK should tolerate being cut'n'pasted from one location to another.

If you're looking for java.exe, the Installshield installer should put it in %windir%\system32, so it is available on the PATH.

You can gain some hints about the location of installed apps by querying the registry:

C:>REG QUERY "HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Development Kit\1.6" /v JavaHome

! REG.EXE VERSION 3.0

HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Development Kit\1.6
    JavaHome    REG_SZ  C:\dev\Java\jdk1.6.0_05

However, you can't rely on this absolutely because this makes some assumptions about vendor, version and installation mechanism.