Hello there. In this lesson, we'll talk about web application security. So, let's start. A web application is accessed using a web browser over a network such as the internet or a company's intranet. As you know, the Java EE platform uses a distributed, multi-tiered application model and web applications run in the web tier. Web applications contain resources that can be accessed by many users. These resources often traverse unprotected open networks such as the Internet. In such an environment, a substantial number of web applications will require some type of security. In the Java EE platform, web components provide the dynamic extension capabilities for a Web server. Web components can be Java servlets or Java server faces pages. 

The interaction between a web client and a web application is illustrated in this figure. Certain aspects of web application  security can be configured when the application is installed or deployed to the web container. Annotations and or deployment descriptors are used to relay information to the deployer about security and other aspects of the application. Specifying this information in annotations or in the deployment descriptor helps the deployer set up the appropriate security policy for the web application. Any values explicitly specified in the deployment descriptor override any values specified in annotations. Security for Java EE web applications can be implemented in various ways.

Declarative security can be implemented using either metadata annotations or in applications, deployment descriptor. Programmatic security is embedded in an application and can be used to make security decisions when declared of security alone is not sufficient to express the security model of an application. Declarative security alone may not be sufficient when conditional login in a particular workflow that is required in the middle of an application. Servlets 3.0 provides the authenticate login and log-out methods of the HttpServletRequest interface. With the addition of the authenticate login and log-out methods to the surveillance specification and application development  descriptor is no longer required for Web applications but may still be used to further specify security requirements beyond the basic default values. Message security works with Web services and incorporate security features such as digital signatures and encryption into the header of a soap message. Working in the application layer, ensuring end-to-end security. Message security is not a component of Java EE and is mentioned here for informational purposes only. So, that's it for now. Hope to see you in our next lesson. Have a nice day.