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Usually, Web web applications that are deployed in production environments depend on external, third-party libraries for different functionality. The WSO2 Web web application management feature provides the capability to load classes from different locations to your applications.

Through the WSO2 Application Server's runtime environment, you can control class loading per server /or application. The default runtimes are sufficient for most users, but you can also define your own runtimes. There are three default run-times available so far , which are namely as follows:

• Tomcat  Tomcat Environment : This is the minimal runtime, which is identical to a pure Tomcat runtime. It only has Tomcat, ServeletServlet, JSP, EL , and JSTL available in the server-level classpath. If you want additional JarsJARs, you should package them with the Web web application or place them in the Tomcat environment's extension directory.
• Carbon  Carbon Environment : This consists of both the Tomcat environment and the WSO2 Carbon runtime. It does not provide CXF or Spring dependencies. If you want additional JarsJARs, you should package them with the Web web application or place them in the WSO2 Carbon environment's extension directory.
• CXF Environment : This consists of the Tomcat environment, CXF and Spring. It does not provide the WSO2 Carbon runtime. If you want additional JarsJARs, you should package them with the Web web application or place in the CXF environment's lib directory.

Next, let's take a look at The subsequent sections explain how to place your external dependencies in a running Carbon server in order , to configure class loading per application or server.

Configuring Class Loading

To configure class loading, you should add the class-loading configuration in a file by the name named webapp-classloading.xml, and  and place it in the META-INF directory of a Web web application. All the artifacts related to a Web web application is are saved in the following directory: <PRODUCT_HOME>/repository/deployment/server/<Web_Application_Type>/<Web_Application_Name>.

For example, : 

<PRODUCT_HOME>/repository/deployment/server/jaxwebappswebapps/SampleApp.

The webapp-classloading.xml file xml file takes following format.

<Classloading xmlns="http://wso2.org/projects/as/classloading"> 
   <Environments>{Runtime Environment Names} </Environments> 
</Classloading> 

Shown below is the webapp-classloading.xml file configuration to specify CXF as the runtime environment:

...

You might want to access some Carbon features in a CXF application. To achieve this, specify a comma-separated list of environments in webapp-classloading.xml file. The following example specifies both CXF and Carbon as the runtime environments:

...

You can share dependencies with a number of applications without packaging them with each and every one of them. To do this, place the common dependencies in the following directories depending on your environment.

• In Tomcat Environment - <PRODUCT_HOME>/lib/runtimes/ext
• In Carbon Environment - <PRODUCT_HOME>/repository/components/lib
• In CXF or any Custom Environment – Use the environment's lib directory.
  For example, :
   <PRODUCT_HOME>/lib/runtimes/cxf

Adding Custom Runtime Environments

To define custom runtime environments, add a new element as <ExclusiveEnvironments> in the <PRODUCT_HOME>/repository/conf/tomcat/webapp-classloading-environments.xml file.  

The following steps explain how to To define a custom runtime environment for Spring.1.

1. Modify the webapp-classloading-environments.xmlfile with the following entries.

   Code Block
   language html/xml
   <ExclusiveEnvironments> <ExclusiveEnvironment> <Name>Spring</Name> <Classpath>${carbon.home}/lib/runtimes/spring/*.jar;${carbon.home}/lib/runtimes/spring/</Classpath> </ExclusiveEnvironment> </ExclusiveEnvironments>

...

1. Next, create and copy of the related Spring dependencies

...

1. in the <PRODUCT_HOME>/lib/runtimes/spring directory.

...

1. Add the following entries to the webapp-classloading.xml file of each

...

1. web application, to use them in the Spring runtime environment defined above.

   Code Block
   language html/xml
   <Classloading xmlns="http://wso2.org/projects/as/classloading">

...

1. <Environments>Spring,Carbon</Environments> </Classloading>

    

...

The CXF runtime environment comes by default with core CXF 2.7.3 5 and core Spring 3.0.7 dependencies. If you want to upgrade to a different CXF version, there are two recommendations:

• Upgrade the CXF runtime environment : You can replace the existing CXF/Spring dependent

Jars

• JARs in the <PRODUCT_HOME>/lib/runtimes/cxf directory, with new CXF/Spring

Jars

• JARs.

• Instead of upgrading server-level CXF dependencies, you can package all the required

Jars

• JARs in the Web-INF/lib directory of the

Web

• web application and deploy that in the Tomcat runtime environment.

If you want to add optional CXF/Spring jars JARs, copy them to the <PRODUCT_HOME>/lib/runtimes/cxf directory after ensuring that they are compatible with the existing JarsJARs.