EAServer supports multile JDK versions, and each JDK version can support multiple VM types such as Server Hotspot, Client Hotspot, and Classic. You specify the JDK version and VM type when starting the server, or for servers that run as Windows services, with the command that you run to install the service. For details, see “Starting the server” in the EAServer System Administration Guide.
As a general rule, you should use the Server Hotspot VM in the latest supported JDK version. However, always consult the EAServer Release Bulletin for your platform for updated recommendations. For more information on Java Hotspot technology, see the Sun Microsystems white paper Java HotSpot Performance Engine Architecture.
Some applications may run significantly faster if compiled
and run with JDK 1.5. JDK 1.5 provides the StringBuilder class
as a faster alternative to StringBuffer. JSPs
and other code that makes extensive use of string concatenation
can run faster in JDK 1.5 due to the use of StringBuilder.
To realize the performance benefits of JDK 1.5, you must compile
your applications with JDK 1.5, and specify the -jdk15 option
when deploying them to EAServer. For more information on deploying,
see the deploy reference
page in Chapter
12, “Command Line Tools,” in the System Administration
Guide.
Switching back to JDK 1.4 from JDK 1.5
Classes compiled with JDK 1.5 cannot be run in JDK 1.4 or
earlier JDK versions. Since EAServer generates new classes for deployed
applications, applications deployed with JDK 1.5 may not run if
the server is restarted with JDK 1.4. To switch back to JDK 1.4
from JDK 1.5, undeploy and redeploy any applications that were deployed
to the server running in JDK 1.5. Applications deployed to JDK 1.4
must also be compiled with JDK 1.4 (or with JDK 1.5 while specifying
JDK 1.4 compatiblity with the -source
1.4 option to javac).
