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External web-application configuration in Tomcat

There's a web application and a number of environments in which it works. In each environment it has different settings like DB connection and SOAP ends-points that in their turn are defined in properties-files and accessed in the following way:
config.load(AppProp.class.getClassLoader().getResourceAsStream(
PROPERTIES_FILE_PATH + PROPERTIES_FILE_NAME));
Thus the WAR-files are different for every environment.
What we need is to build a unified WAR-file that doesn't contain any configuration and works in any environment (for now, Tomcat instance) getting its configuration from outside its WAR-file.
The answer Java Web Application Configuration Patterns, to my mind, gives the full set of common approaches but with just few examples. The most attractive way is configuring JNDI lookup mechanism. As I can guess it allows to separately configure web-applications by their context paths. But couldn't find a simple (step-by-step) instructions in both the Internet and the Tomcat's docs. Unfortunately cannot spend much time on studying this complicated stuff in order to just meet so seemingly simple and natural demand :(
Would appreciate your links at the relevant descriptions or any alternative suggestion on the problem.

If its a case of simply deploying your WAR on different environment (executed by different OS user), then you can put all your config files in the user's home folder and load them as:
config.load(new FileInputStream(System.getProperty("user.home") + PROPERTIES_FILE_NAME));
This gives you the isolation and security and makes your WAR completely portable. Ideally though, you should still provide built-in default configuration if that makes sense in your case.

The approach we've taken is based on our existing deployment method, namely to put the WAR files in the filesystem next to the Tomcat, and deploy a context.xml pointing to the WAR file to Tomcat.
The context descriptor allows for providing init parameters which is easily accessible in a servlet. We've also done some work on making this work with CDI (for Glassfish and TomEE dependency injection).
If you only have a single WAR file deployed to this Tomcat instance, you can also add init parameters to the default global context XML. These will be global and you can then deploy the WAR file directly. This is very useful during development.

WebSphere liberty class loading PARENT LAST as default

I have been investigating using WebSphere's Liberty profile as a light weight alternative to having a fully fledged WebSphere instance deployed on my local machine (late to the party, I know).
1 thing that I can not figure out:
How do I set Parent Last class loading to be default?
I want to deploy any application and have it automatically be parent last.
I am aware that I can deploy an EAR with the deployment.xml to trigger parent last class, or run a Jython script. However, I would rather have it be the default behavior.
Any ideas anyone?
WebSphere Version: Liberty 8.5.5.8

If you're trying to set parent-last classloading in Liberty because you had to do so in WebSphere Application Server traditional to resolve library conflicts, you should first try the application on Liberty without changing it's configuration because Liberty was designed to avoid those types of conflict. If, after that, you're still inclined to change the configuration, while you can't set it as the default, you can do something like this in your server.xml:
<enterpriseApplication location="myApp.ear" name="MyApp">
<classloader delegation="parentLast"/>
</enterpriseApplication>

reflect on web-application changes in servlets class file

I just want to know how to make automatic reflect on web application if i make changes in my servlets class file .
Because when ever I make changes in servlets class file I have to do server shutdown and startup
Otherwise go to tomcat web application manager
And reload the web-application
Is there another method which automatic do this

Set <Context reloadable="true" />, Catalina to monitor classes in /WEB-INF/classes/ and /WEB-INF/lib for changes, and automatically reload the web application if a change is detected. This feature is very useful during application development. But not in production environment. See the reloadable doc.
Edit:
How to set context

Edit install_dir/conf/server.xml and add a DefaultContext subelement to the main Service element and supply true for the reload able attribute
Add
<DefaultContext reloadable="true"/>
before the
</host>
tag.

Preventing ViewExpiredException with JSF 2 after redeploy

I have a problem where every time I redeploy my app, any existing sessions are broken and the requests result in a ViewExpiredException. None of the advice in related questions or outside mailing list / forum posts seems to fix this issue. I can redeploy the same WAR file completely unchanged and the behavior is the same.
I'm using Apache MyFaces 2.2.0, Tomcat 7.0.56 and Primefaces 5.0.
The message of the exception is No saved view state could be found for the view identifier: with whatever page would be requested. Primefaces' menubar is used for navigation, which seems to be implemented as a <form> with POST requests. These messages occur both with those navigation options and other AJAX that uses POST.
I have tried:
Setting explicit org.apache.myfaces.SECRET and org.apache.myfaces.MAC_SECRET values, as seen in this document.
Both client and server values for the javax.faces.STATE_SAVING_METHOD parameter.
Ensuring all beans and their transitive fields are serializable. No serialization errors are reported in the logs.
Using a filter to add no-cache headers, e.g. as suggested in this answer.
Session persistence is not disabled, that is my context.xml has <Manager pathname="" /> commented out.

try with:
<Manager className="org.apache.catalina.session.PersistentManager" saveOnRestart="true"/>

It seems that losing sessions is a "feature" of Tomcat since at least version 6 and continuing to version 7 when deploying via WAR file. We have to copy an unpacked directory to avoid losing the sessions, because WAR changes cause an undeploy followed by a deploy, as opposed to a reload.
This bug report states:
There are ways to achieve an update to an application without dropping the sessions. The simplest is probably:
- deploy as an exploded directory rather than a WAR
- update the files
- touch web.xml to trigger a reload
The reason for the current behaviour is to prevent problems when WARs are updated in incompatible ways and anything other than a full undeploy followed by (essentially) a new deployment causes conflicts.
This is still the case in the current Tomcat 7.0 documentation:
Currently, application reloading (to pick up changes to the classes or web.xml file) is not supported when a web application is deployed directly from a WAR file. It only works when the web application is deployed from an unpacked directory.

Short url or alias for deployed application in tomcat 6

I have a web application project which is deployed in tomcat 6.
I can access my application using the url:
http://localhost:8082/MyApplication
I also wan't to be able to access this application by another url like:
http://localhost:8082/myapp
Is this possible ? if yes what alternatives do i have ?
Off course, I don't want to change the original name of the application('MyApplication').
Thanks,
Abhishek.

If you add the Context within server.xml it will work as you want. Give the path attribute you wish.
<Context docBase="MyApplication" path="/myapp" />
Though it works, this approach is not recommended by the Tomcat docs, since any changes to server.xml means restarting the server disturbing all the web apps.
But, on the flip side, the practice of keeping this in Catalina_Home/conf/Catalina/localhost/context.xml (which is recommended by the docs) has some unreliabilities as others have reported - when you redeploy the war you can lose the context.xml too
See Why-does-tomcat-replace-context-xml-on-redeploy and
Why does tomcat like deleting my context.xml file?