Technical Tips

• How can I protect myself from Java crashes?
• What are the different ways that I can shutdown my Java application?
• How can I schedule JVM restarts, shutdowns, thread dumps, or other actions with my Java applications?
• How can I protect myself from Java freezes?
• How can I access mapped Windows shares from my Java Service?
• How can I run my Java application as a Windows Service?
• How can I protect myself from Deadlocks in my Java application?

Java as a language was designed to make it impossible for user developed code to result in an application crash. Any error would result in a nice clean exception being thrown which could be caught, and then handled appropriately.

The reality, as any long time Java developer or system administrator knows, is that the Java Virtual Machine (JVM) itself can and does crash. This is because the JVM is itself a program written in native code, and like any very large complicated program, the JVM has some bugs in it.

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When people first start using the Java Service Wrapper, they are usually interested in how to integrate their application with the Java Service Wrapper to run as a Service or to have their application monitored. Once an application is setup and integrated with other systems however, the question of how to shutdown often comes up.

In this Tech Tip, we have gone through the API and collected all of the various ways you can shutdown the Wrapper in one place. There are probably a few tips which even experienced Wrapper users are not aware.

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What if your application is suffering from a memory leak which requires the JVM to be restarted at least once per week? Or if your application needs to be taken down for 10 minutes every night to allow external backups to take place? Or you may simply want to schedule that some more benign action takes place once every 5 minutes.

In this Tech Tip, we are will introduce you to Wrapper timers, which make it possible to schedule all kinds of actions in a platform independent way and then deploy them with the rest of your application.

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When a mission critical system starts hanging or freezing, it can be a nightmare situation for the system administrator, development team, and everyone who makes use of the system. Identifying and fixing the problem can take days or even months in some cases. In the mean time the system is in active use and needs to stay running. For many organizations, every minute a system is down not only has a direct effect on sales, but also on the reputation of the organization and teams managing the system.

The Java Service Wrapper is able to detect most JVM freezes very quickly, restart the application, and then send a report of what happened so a human administrator can double check to make sure everything is working correctly. In most cases, this can reduce downtime from hours to seconds so end users are often not aware that there was ever a problem.

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In Windows environments is common for users to map network drives and printers so they can be accesed by their local system. Windows Services often have the same requirements, but Windows makes it very difficult for services to access those shares when the service is launched on system startup. Often services will have access to shares when started in a running system, but the shares will not be accessible when the system is rebooted.

The Java Service Wrapper makes it possible to configure and access network drives and printers reliably without the need for a user to be logged in.

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Java applications running on Windows systems tend to be run in a console on a Desktop because of Java's lack of the ability to run as a Windows Service. This has a number of disadvantages; security issues because a user is logged in, system performance due to the unwanted Desktop, and the simple risk that a user might press the wrong key and affect the console, to name a few. Many applications solve these problems by running as a Windows Service, all without the need to write a single line of code in most cases.

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Most applications go through a series of rigorous tests before being deployed or released. As we all know however, in the real world unexpected problems can be encountered. Unfortunately, one common problem with large multi-threaded applications are deadlocks. They can be fatal and very difficult to track down and fix.

The Java Service Wrapper includes the ability to automatically monitor your application for deadlocks in a very light weight way which causes almost no change in performance. When a deadlock is detected, the Wrapper is able to immediately respond in the way you want it to. At the same time, it will also record the precise conditions of the deadlock so a developer can easily fix it.

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