Faq ID	6
Product	ServletExec
Category	Installation, VM Settings
Question	On Windows, how does ServletExec/ISAPI and ServletExec/NSAPI determine which JDK or JRE to use?
Answer	This information can be found in the ServletExec Installation Guide. For example in both the SE 5.0 & 4.2 Installation Guides, it can be found in section 2.2.3.1 Here is some of that information: The very first time that ServletExec ISAPI or NSAPI on Windows starts up it must do so using Sun Microsystem's JVM. ServletExec determines which JDK or JRE to use by looking at the JavaSoft entries in the Windows registry. It first looks for a JDK/SDK. If a JDK is not found it then looks for a JRE. ServletExec looks for a JDK by checking the following registry entries (in the given order): HKLM\SOFTWARE\JavaSoft\Java Development Kit\CurrentVersion HKLM\SOFTWARE\JavaSoft\Java Development Kit\<version-number>\JavaHome ServletExec looks for a JRE by checking the following registry entries: HKLM\SOFTWARE\JavaSoft\Java Runtime Environment\CurrentVersion HKLM\SOFTWARE\JavaSoft\Java Runtime Environment\<version-number>\JavaHome You can verify that a JDK or JRE is installed on your machine by performing the following steps: To verify that a JDK is properly installed, use Regedit to check the JavaSoft registry entries. The following registy entry should contain the JDK version number (for example, "1.5", or "1.4", or "1.3"): HKLM\SOFTWARE\JavaSoft\Java Development Kit\CurrentVersion The following registy entry should contain the path to the installation directory for the JDK (for example, "C:\j2sdk1.4.0"), where <version-number> is the value from the CurrentVersion registry entry, above: HKLM\SOFTWARE\JavaSoft\Java Development Kit\<version-number>\JavaHome To verify that a JRE is installed, check the JavaSoft registry entries. The following registry entry should contain the JRE version number (for example, "1.5", or "1.4", or "1.3"): HKLM\SOFTWARE\JavaSoft\Java Runtime Environment\CurrentVersion The following registry entry should contain the path to the installation directory for the JRE (for example, "c:\program files\javasoft\jre"), where <version-number> is the value from the CurrentVersion registry entry, above: HKLM\SOFTWARE\JavaSoft\Java Runtime Environment\<version-number>\JavaHome Verify the JAVA_HOME environment variable is not set. If it is set, then verify it is correctly set to the installation directory of the JDK or JRE you are using, based on the JavaSoft registry entries as described above. Once ServletExec is initialized and running with the Sun JVM for the first time, you can then choose to use the IBM JDK on the VM Settings page of the ServletExec Admin UI. If the IBM JDK is selected then the next time ServletExec is initialized it will look for the IBM JDK or JRE by checking the IBM registry entries in the manner described in the ServletExec Installation Guide. If one isn't found then it will try to find a Sun JDK or JRE. The last version of ServletExec to support the Microsoft VM was SE 3.1. If you are using SE 3.1 and the Microsoft VM is selected on the VM Settings admin page of the SE admin UI, then the next time ServletExec is initialized it will look for the Microsoft VM by trying to load C:\WINNT\System32\msjava.dll. If it can't, then it will try to find a Sun JDK or JRE.