Features provided by the Application Servers in which applications can be automatically deployed / undeployed on to the server. The App Server provides a mechanism where they scan certain folders for the applications for ex.autoDeploy folder in weblogic, deploy folder in tomcat / Jboss etc.
The process of adding new components (such as WAR files, EJB Jar files, enterprise Java beans, servlets, and JSP files) to a running server without having to stop the application server process and start it again.
Hot deployment is mainly used to update the individual modules or jsps/servlets/classes in a module without redeploying the complete app.
Auto Deployments of Web Applications in WebLogic Server:
This is the simplest form of deployment. When enabled the Admin Server periodically scans the autoDeploy folder and deploy all the applications present in there.
Note: This feature is disabled in the production mode.
Production mode of the application server can be changed using the handle –Dweblogic.ProductionModeEnabled=true in the server startup file.
Need of Auto Deployment:
This is a very quick way of deploying the application which can be using during development and unit testing phase to reduce the deployment time.
How to auto Deploy:
- Start the WebLogic Server domain in development mode.
- Place the application’s exploded directory structure or archive file in this autodeploy directory.
It is present under $DOMAIN_HOME folder structure.
Hot Deployment (Redeployment Strategies) in Weblogic server:
This can be achieved by using different Redeployment Strategies.
Production redeployment strategy involves deploying a new version of an updated application alongside an older version of the same application. WebLogic Server automatically manages client connections so that only new client requests are directed to the new version. Clients already connected to the application during the redeployment continue to use the older version of the application until they complete their work, at which point WebLogic Server automatically retires the older application.
In-place redeployment immediately replaces a running application’s deployment files with updated deployment files. In contrast to production redeployment, in-place redeployment of an application or stand-alone J2EE module does not guarantee uninterrupted service to the application’s clients. This is because WebLogic Server immediately removes the running classloader for the application and replaces it with a new classloader that loads the updated application class files.
Partial Redeployment of Static Files:
WebLogic Server enables you to redeploy selected files in a running application, rather than the entire application at once. This feature is generally used to update static files in a running Web application, such as graphics, static HTML pages, and JSPs. Partial redeployment is available only for applications that are deployed using an exploded archive directory.
Partial Redeployment of J2EE Modules :
Partial redeployment also enables you to redeploy a single module or subset of modules in a deployed Enterprise Application. Again, partial deployment is supported only for applications that are deployed using an exploded archive directory.