Java Runtime Environment Configuration


  JDK Documentation

This document applies to JRE installers starting in Java SE 6 update 10 release. This feature is available only to installers running on Microsoft Windows.

In the past, when a user installed different versions of a Java Runtime Environment (JRE), the user would be left with multiple installation directories and several entries in the Add/Remove Programs dialog in the Control Panel. This resulted in unnecessary proliferation of unused JREs.

The JRE can now be installed in two configurations: patch-in-place and static. JRE updates may be configured to patch a pre-existing installation or do a brand new installation.

The JRE may be installed in silent (unattended) or non-silent modes. For more information on silent install and uninstalling a silent installation, please see Silent Installation.

Patch-in-place configuration

The patch-in-place mode implies that when a version of the JRE exists on a machine, any updates belonging to the same JRE family will be done in place, meaning, the existing JRE will be patched with changes. A JRE is installed in patch-in-place mode by default. The default installation directory is c:/Program Files/Java/jre<n> where n is the Java SE minor version number (for example, n = 6 for version 1.6.0_10).

For example, if a user has previously installed JRE 6u10 in the c:/Program Files/Java/jre6 directory, and now attempts to install JRE 6u14, the version 6u14 installer does not create a new directory. Instead, it updates the pre-existing c:/Program Files/Java/jre6 directory with the new 6u14 content. The user is left with the 6u14 JRE only. The 6u10 JRE no longer exists.

Static configuration

When a JRE is installed in the static mode, it will not be updated in place by newer versions. A later version of the same JRE family will be installed in a separate directory. This mode ensures that vendors, who require a specific version of the JRE for their product, can be certain that the JRE will not be overwritten by a newer version.

Some of the characteristics of a static JRE installation are as follows:

  • A static JRE installation (example: 6u15) will ignore a previous patch-in-place installation of another JRE (example: 6u10)
  • A static JRE installation is never overwritten by another JRE version
  • When a newer JRE version is present (example: 6u15), older JRE versions ( example: 6u12) are installed in static mode only
  • A patch-in-place JRE can be overwritten by a static JRE installation of the same version. The user will be left with one static JRE installation.

The default installation directory of a static JRE is of the form c:/Program Files/Java/jre<version>. For example, by default, a static JRE for Java SE 6u10 will be installed in the directory c:/Program Files/Java/jre1.6.0_10.

See Java Runtime Environment Update Scenarios to see examples of how the installer behaves.