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Some Background

WebSphere controls whether applications (EARs and WARs) are in PARENT_FIRST or PARENT_LAST classloading mode by its deployment.xml. RAD, or Rational Application Developer, has tools to generate this, as does the application server itself, but the Eclipse plugins do not at the time of this writing. So how do you configure your applications?

Wait, what does the classloading mode do?

Simply, when your application attempts to load a class, say IOUtils from Apache Commons IO, the JVM needs to know what to do when it finds multiple classes with the same fully qualified name. You could have classes provided by your application server, global JARs that you have put into your application server, and JARs in your application.

_PARENT_FIRST _classloading means take classes found in WebSphere (the parent), or global JARs first. So if you bundle a version of Apache Commons IO that doesn’t match the parent version, your application will run with the parent version instead of your application’s version.

_PARENTLAST classloading means prefer your application’s first.

So what’s the problem?

Imagine this scenario:

  • Your servers have global JARs setup that specific applications running in the same WebSphere profile require
  • You start a new application in your local development environment and you don’t realize the server has overridden certain JARs
  • You bundle newer versions of those JARs in your application
    So, with the “It works on my machine” stamp of approval you push to your servers only to find… failure.

There are plenty of other scenarios that could lead to an issue as well.

What’s the silver bullet?!

Unfortunately, there is no silver bullet. You may want to re-evaluate having shared libraries, update their versions, change the classloading mode of your application, or use a different WebSphere profile. The right answer really depends on your environment, but if changing the classloading mode is right for you, read on!

Changing the classloading mode

There are a few ways to make this change:

  • Deploy your application to WebSphere and update the configuration in the admin console (or wsadmin)
  • Use RAD (Rational Application Developer) to change it, if you have RAD
  • Or, use a new tool that I’ve created!

Generating deployment.xml in WebSphere

To obtain a deployment.xml from WebSphere:

  1. Build your application as an EAR
  2. Manually install it to WebSphere (via your admin console at http://localhost:9060/ibm/console for example)
  3. Open your application in the admin console and configure your EAR’s classloader mode
  4. Use Manage Modules to configure the WARs’ classloader modes
  5. Save your changes to WebSphere
  6. Export your application from the admin console as an EAR
  7. Copy its ibmconfig with deployment.xml deeply nested in it

Generating deployment.xml in RAD

Generating deployment.xml in RAD is much easier:

  1. Right click your EAR
  2. Go to Java EE -> Open WebSphere Application Server Deployment
  3. Scroll to the bottom and configure classloader settings as desired

Comparing WebSphere’s generated deployment.xml to RAD’s

Updating the configuration in WebSphere generates a deployment.xml that you may not want to re-use. Let’s take a look at the differences:

WebSphere’s version

deployment.xml
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<?xml version=“1.0” encoding=“UTF-8”?>
<appdeployment:Deployment xmlns:appdeployment=“http://www.ibm.com/websphere/appserver/schemas/5.0/appdeployment.xmi“ xmlns:xmi=“http://www.omg.org/XMI“ xmi:version=“2.0” xmi:id=“Deployment_1428026415557”>
<deployedObject xmi:type=“appdeployment:ApplicationDeployment” xmi:id=“ApplicationDeployment_1428026415557” deploymentId=“0” startingWeight=“1” binariesURL=“$(APP_INSTALL_ROOT)/WIN-F8QH15674T8Node02Cell/JpaExample.ear” useMetadataFromBinaries=“false” enableDistribution=“true” createMBeansForResources=“true” reloadEnabled=“false” appContextIDForSecurity=“href:WIN-F8QH15674T8Node02Cell/JpaExample” filePermission=“..dll=755#..so=755#..a=755#..sl=755” allowDispatchRemoteInclude=“false” allowServiceRemoteInclude=“false” asyncRequestDispatchType=“DISABLED” standaloneModule=“false” enableClientModule=“false”>
<targetMappings xmi:id=“DeploymentTargetMapping_1428026415557” enable=“true” target=“ServerTarget_1428026415557” />
<modules xmi:type=“appdeployment:WebModuleDeployment” xmi:id=“WebModuleDeployment_1428026415557” deploymentId=“1” startingWeight=“10000” uri=“JpaExampleWeb.war” classloaderMode=“PARENT_LAST” containsEJBContent=“0”>
<targetMappings xmi:id=“DeploymentTargetMapping_1428026415558” target=“ServerTarget_1428026415557” />
<classloader xmi:id=“Classloader_1428026415558” />
</modules>
<classloader xmi:id=“Classloader_1428026415557” mode=“PARENT_LAST” />
<properties xmi:id=“Property_1428026415557” name=“metadata.complete” value=“false” />
</deployedObject>
<deploymentTargets xmi:type=“appdeployment:ServerTarget” xmi:id=“ServerTarget_1428026415557” name=“server1” nodeName=“WIN-F8QH15674T8Node02” />
</appdeployment:Deployment>

RAD’s version:

deployment.xml
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<?xml version=“1.0” encoding=“UTF-8”?>
<appdeployment:Deployment xmlns:appdeployment=“http://www.ibm.com/websphere/appserver/schemas/5.0/appdeployment.xmi“ xmlns:xmi=“http://www.omg.org/XMI“ xmi:version=“2.0” xmi:id=“Deployment_1423511656329”>
<deployedObject xmi:type=“appdeployment:ApplicationDeployment” xmi:id=“ApplicationDeployment_1423511656329” startingWeight=“10”>
<modules xmi:type=“appdeployment:WebModuleDeployment” xmi:id=“WebModuleDeployment_1423511656329” startingWeight=“10000” uri=“JpaExample.war” classloaderMode=“PARENT_LAST” />
<classloader xmi:id=“Classloader_1423511656329” mode=“PARENT_LAST” />
</deployedObject>
</appdeployment:Deployment>

The differences

Primarily, the WebSphere version includes node/cell specifics. If you take that version and deploy to a different server, you will end up with new folders in your profile/installedApps directory. This doesn’t cause any issues (that I’ve experienced) but its annoying.

A better solution for non-RAD users

If you take a look at the RAD version, its pretty basic and just lists the applications deployed and which classloading mode they are in. The ids are a standard format with the time after them.

So, assuming you are not using anything else in deployment.xml, this file is easy to reproduce! And to make it easier, I created a command line application to do it for you!

https://github.com/craigstjean/WebSphere-Deployment-Xml-Tool

To use it, invoke the JAR, passing it your application.xml as the first parameter, followed by either:

  • Nothing (which shows you its menu)
  • list (lists the EAR and all web application’s classloading mode)
  • set parent first (sets the EAR and all web applications to PARENT_FIRST)
  • set parent last (sets the EAR and all web applications to PARENT_LAST)
    For example:
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java -jar WebSphere-Deployment-Xml-Tool.jar C:\workspace\MyProject\MyEar\META-INF\application.xml set parent last

And that’s it!

If you have any troubles with it, please create a GitHub issue and I’ll take a look!

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Settings button

When working in Eclipse or RAD, I immediately start modifying my environment. Here are some of the changes that I make that might improve your day, please feel free to share you own!

Stop the Servers tab from taking over!

Whenever server state changes (e.g. from Stopped to Starting, to Started, to Republish, etc), the Servers tab automatically shoves its way onto your screen because it wants you to know it did something. Great! But if you’re like me, you immediately dismiss it and now you’re a little distracted and a little annoyed. Here’s how to turn it off!

From within Eclipse’s / RAD’s preferences, click Server. Then uncheck “Show Servers view when server state changes.”

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Stop the Console tab from taking over!

Now that we stopped the Servers tab, let’s do the same thing for Console! Output is constantly written to the console, and I typically look at it when I want it, and otherwise don’t care. So, go to preferences, expand Run/Debug, and click Console. Then uncheck “Show when program writes to standard out,” and “Show when program writes to standard error.”

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Where did my Console output go? And why can’t I scroll up?!

The Console view defaults to limiting its output. This may make it easier to work with, but has the nasty side-effect of dropping important content when you have large stack traces, or multiple stack traces. To turn it off, go to the Console preferences (from above) and uncheck “Limit console output”.

Makes your static imports work in autocomplete! (e.g. JUnit, Mockito, etc.)

UNIT TESTING! Ok, ok, let’s calm down a little. If you write a lot of tests, and you use JUnit, Mockito, EasyMock, etc., or if you happen to use a library that leverages static imports, you are probably tired of manually adding them to your imports list. But, _you don’t have to! _Go to the preferences, expand Java, then Editor, then Content Assist and click Favorites. Then, click “New Type” and type in org.junit.Assert. Eclipse will add org.junit.Assert.* to the favorites list, and now when you are writing your unit tests you can start typing assertEq, hit Control + Space, and it will autocomplete the static import and add it to your class!

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Other, more personal editor settings.

These settings are definitely up to personal preference, but in case you want to give them a try here are some other changes I make:

Use Spaces, not Tabs

You should be using Spaces and never tabs**! **_I’m kidding!!! _Since I have no interest in arguing my personal preferences, here is how you make the change in case you want to: open preferences, expand General, expand Editors, and click Text Editors. Then, check “Insert spaces for tabs” (or don’t).

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Auto format and auto organize imports on save

Why should I have to worry about constantly re-indenting my code, fixing it up, etc.? My time is better spent doing other things, you know like writing code instead of styling it. So, I set my formatter preferences, then go to preferences, expand Java, then Editor, then click Save Actions. Then I check “Perform the selected actions on save,” “Format source code,” and “Organize imports.” My personal feeling towards this is you will feel much more free if you make the change, if you can live with the formatter settings you choose. Give it a try!

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What changes do you make?

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Craig St. Jean

Father, programmer, constant learner, @pluralsight author


Software Architect