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What is the Java Service Wrapper? |
What is the Java Service Wrapper?
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NOTE
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The Java Service Wrapper continues to be actively developed. Each new
version is the culmination of a great deal of time and energy in development,
testing, documentation and user support.
While the Wrapper is being used within a number of open sourced projects,
by far the majority of our user base is directly or indirectly making use of
the Wrapper to support commercial applications and or commercial
infrastructure.
We urge all of our users to please review the value that the Wrapper is
providing to your organization. The Wrapper team develops and maintains
the Wrapper on a volunteer basis, but the time and effort involved is real.
Please help us to keep the Wrapper project alive, free, and growing, by
showing your appreciation and support for the project with a
donation to the team.
We would also like to thank all of our users for the ongoing feedback which
has helped us to continuously improve the Wrapper over time.
Sincerely,
The Java Service Wrapper team.
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As with any application, reading through the documentation the best
way to get started. But realizing the desire to get your feet wet
quickly, you should glance over this page to get a feel for what the
Wrapper can do.
Then to get up and running , at a minimum you will need to read over
the Integration Page.
There you will be presented with 3 integration methods. From the
overviews, choose the one that best meets your needs and then proceed
to read over the page dedicated to that integration method.
The Wrapper provides a very large feature set. At some point
it is suggested that you look over the
full properties list to get a
feel for the full power of the Java Service Wrapper.
If you run into problems or have any questions, the preferred method
for getting help is posting a message to the
wrapper-user mailing list.
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The Java Service Wrapper is an application which has evolved out of a
desire to solve a number of problems common to many Java applications:
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The Wrapper makes it possible to install a Java Application as a
Windows NT Service. The scripts provided with the Wrapper also
make it very easy to install those same Java Applications as
daemon processes on UNIX systems.
The Wrapper correctly handles user log outs under Windows, service
dependencies, and the ability to run services which interact with
the desktop.
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Application Reliability. As the use of Java expands, applications have
been written to provide a variety of mission critical services. These
services must be able to provide a high level of reliability. In an
ideal world, only software which is 100% bug free will ever be released
and installed. However, history has shown this not to be the case.
Almost every application suffers from quality issues at one point or
another during their life-cycle. Applications hang, crash, run out of
memory or suffer from any number of problems. Where possible, problems
are fixed quickly without significant service outages. There are times,
however, when fixing a problem can be prohibitively expensive or
impossible to solve in a short time period.
The Wrapper monitors a JVM process and automatically restarts it if it
that the JVM has crashed or hung. This process takes just a few seconds
once the Wrapper has decided there is a problem. There is also a way to
configure the Wrapper to
monitor the console output of a JVM and react to certain strings by
restarting or shutting down the JVM.
While these features will not make every problem go away, they will help
you to sleep easier knowing that if there is a problem, the Wrapper will
be there to keep things up and running until you can get into the office
to check the logs. Say goodbye to that pager!! (Or as so as not to date
myself, that cel phone!)
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Write once run everywhere configuration. Java has been marketed as a
"Write Once, Run Everywhere" programming language. While this is true
for many aspects of an application, the developer is often plagued with
having to write complicated, platform specific scripts which are tasked
with building up class paths and collecting other system information
necessary to launch an application.
The Java Service Wrapper helps to relieve the developer of this task
by providing a set of scripts for a wide range of platforms that can be
used as is to launch almost any Java Application controlled by the
Wrapper.
The Wrapper moves all JVM configuration into a platform independent
configuration file. See the
integration examples for details.
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The Wrapper provides a way for a Java Application to request that
its own JVM be restarted. This can be useful in a number of cases.
Applications may wish to restart after having had their configuration
files modified. Or the application may simply need to be restarted
to avoid problems with a memory or resource leak of some kind.
JVM restarts can be triggered from within the JVM by making a call to
WrapperManager.restart(). See the
Javadocs for more details.
There are also more passive ways to trigger restarts. The Wrapper has
the ability to monitor console output
and trigger shutdowns or restarts whenever certain text is detected.
The Wrapper can also be configured to either restart another JVM
instance or shudown normally depending on the
exit code returned by a JVM.
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The Wrapper provides a wide range of configuration properties which can
be used to configure the JVM in any way possible from the command line.
The Wrapper configuration file also provides a number of properties to
allow you configure things like logging and how the Wrapper is installed
as a service.
See the Configuration Properties
section for details on what is possible. Be sure you have read over
the integration section before
jumping into the configuration file.
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By using the Wrapper's standard scripts, and relative paths in the
configuration file, it is usually possible to create an application
which requires no further installation than simply expanding an
archive file into a directory of the user's choice.
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While the Wrapper does not attempt to, nor should it, replace any
of the great logging tools available, it does provide a number of
properties to configure how stdout and stderr output to the JVM console
is handled. This output can be logged to any combination of the console,
a file, or the Event Log (Windows) or syslog (UNIX).
Logging the output to the JVM console can be critical to tracking down
problems with an application. Without the Wrapper, when a JVM is being
run as a service under Windows, or as a daemon under UNIX, the console
output would normally be lost. The Wrapper makes sure that all console
output is logged.
Java-based logging tools are only capable of logging output generated from
within the JVM. If the JVM crashes or prints out low level messages such
as thread dumps, there is normally no way to log it. The Wrapper logs all
console output from the JVM process regardless of its source meaning that
a record of any crash will survive even after the Wrapper has restarted
the JVM.
See the Logging Configuration
section for further details.
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The Wrapper is known to work with the Sun, IBM, Blackdown and BEA WebLogic
JRockit JVMs without any problems. If you get a chance to test any other
JVMs, please be sure and let us know the results.
NOTE
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The Wrapper can be used with 1.2.x versions however some functions are disabled
due to this version of Java's lack of support for shutdown hooks. Shutdown
hooks were implemented with the 1.3.0 release of Java.
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Binary distributions are provided for the following list of platforms and are
available on the download page.
Only OS versions which are known to work have been listed. If you have had successful
or unsuccessful results running on other OS versions, please post a comment below
and it will be added to the list.
It should be fairly easy to build the Wrapper from source on additional UNIX
platforms. Please let us know and we will update the list.
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aix - AIX
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freebsd - FreeBSD
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hpux, hpux64 -
HP-UX, 32 and 64-bit versions.
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irix - SGI Irix
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linux - Linux kernels; 2.2.x 2.4.x, 2.6.x.
Known to work with Debian and Red Hat, but should work with any distribution.
Currently supported on both 32 and 64-bit x86, and 64-bit ppc systems.
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macosx - Macintosh OS X.
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osf1 - DEC OSF1.
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solaris - Sun OS, Solaris 7, 8, 9 and 10.
Currently supported on both 32 and 64-bit sparc, and x86 systems.
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win32 - Windows NT, 2000, XP, and 2003.
Also known to run on Windows 98 and ME, however due the lack of support for
services in the OS, the Wrapper can only be run in console mode.
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by Leif Mortenson
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