WebSphere Application Server V8.5 Administration and Configuration Guide for the Full Profile

Chapter 24. Updating Java EE applications 899

24.5 Hot deployment and dynamic reloading

Hot deployment and dynamic reloading characterize how application updates are handled

when updates to the applications are made by directly manipulating the files on the server. In

either case, updates do not require a server restart, although they might require an

application restart. These features provide the following capabilities:

 Hot deployment of new components

Hot deployment of new components is the process of adding new components, such as

WAR files, EJB JAR files, servlets, and JSP files to a running application server without

having to stop and then restart the application server.

However, in most cases, such changes require the application itself to be restarted so that

the application server run time reloads the application and its changes.

 Dynamic reloading of existing components

Dynamic reloading of existing components is the ability to change an existing component

without the need to restart the application server for the change to take effect. Dynamic

reloading can involve changes of the following types:

– Implementation of an application component, such as changing the implementation of

a servlet

– Settings of the application, such as changing the deployment descriptor for a web

module

To edit the application files manually, locate the binaries in use by the server (in most cases

these binaries are in the application server installedApps directory). The application files can

be edited manually on one or more of the nodes. These changes are overwritten the next time

the node synchronizes its configuration with the deployment manager. Therefore, perform

manual editing of an application’s files only in the master repository, which is located on the

deployment manager system.

The following settings can affect dynamic reload:

 Reload classes when application files are updated

For application files to be reloaded automatically after an update, the Override class

reloading settings for Web and EJB modules setting must be enabled, and the Polling

interval for updated files setting must be greater than 0.

Click Applications  Application Types  WebSphere enterprise applications, and

click the link for the application. In the Detail properties section, click the Class loading

and update detection link.

 Application Server class loader policy

Set the application server’s class loader policy to Multiple. If it is set to Single, you must

restart the application server after an application update.

Click Servers  Server Types  WebSphere application servers, and click the server

name. The setting is found in the General Properties section, under Server-specific

Application Settings.

Tip: If you are not familiar with updating applications by manipulating the server files

directly, consider using the administrative console update wizard.

900 WebSphere Application Server V8.5 Administration and Configuration Guide for the Full Profile

 JSP Reload options for web modules

A web container reloads a web module only when this setting is enabled, which is a default

setting.

Click Applications  Application Types  WebSphere enterprise applications, and

click the link for the application. In the Web Module Properties section, click JSP and JSF

options and then select the JSP enable class reloading option. Enter a polling interval.

For more information about using hot deployment and dynamic reload, refer to the information

center at the following website:

http://www14.software.ibm.com/webapp/wsbroker/redirect?version=phil&product=was-ba

se-dist&topic=trun_app_hotupgrade