Explore the key concepts pertaining to Web applications. Web applications
are comprised of one or more related files that you can manage as a unit,
including HTML files, servlets, and Java ServerPages (JSP) files. IBM extensions
to the JSP specification make it easy for HTML authors to add the power of
Java technology to Web pages, without being experts in Java programming.
- Web applications
- A Web application is comprised of one or more related servlets, JavaServer
Pages technology (JSP files), and Hyper Text Markup Language (HTML) files
that you can manage as a unit.
- Servlets
- Servlets are Java programs that use the Java Servlet Application Programming
Interface (API). You must package servlets in a Web archive (WAR) file or
Web module for deployment to the application server. Servlets run on a Java-enabled
Web server and extend the capabilities of a Web server, similar to the way
applets run on a browser and extend the capabilities of a browser.
- Application life cycle listeners and events
- With application life cycle listeners and events, which are now part of
the Servlet API, you can notify interested listeners when servlet contexts
and sessions change. For example, you can notify users when attributes change
and if sessions or servlet contexts are created or destroyed.
- Servlet filtering
- Servlet filtering provides a new type of object called a filter that can
transform a request or modify a response. You can chain filters together
so that a group of filters can act on the input and output of a specified
resource or group of resources.
- Page lists
- Page lists allow you to avoid hard-coding Uniform Resource Locators (URLs)
in servlets and JSP files. A page list specifies the location where a request
is to be forwarded, but automatically customizes that location depending on
the MIME type of the servlet. Use these properties to specify a markup language
and an associated MIME type. For the given MIME type, you also specify a set
of pages to invoke.
- Client type detection support
- In addition to providing the page list mapping capability, the PageListServlet
also provides Client Type Detection support. A servlet determines the markup
language type that a calling client needs in the response, using the configuration
information in the client_types.xml file.
- autoRequestEncoding and autoResponseEncoding
- Starting with WebSphere Application Server Version 5, the Web container
no longer automatically sets request and response encodings, and response
content types. Programmers are expected to set these values using available
methods in the Servlet 2.3 Specification or later. If programmers choose not
to use the character encoding methods, they can specify the autoRequestEncoding
and autoResponseEncoding extensions, which enable the application server to
set the encoding values and content type.
- JavaServer Pages
- JavaServer Pages (JSP) are application components coded to the JavaServer
Pages Specification. JavaServer Pages enable the separation of the Hypertext
Markup Language (HTML) code from the business logic in Web pages so that HTML
programmers and Java programmers can more easily collaborate in creating and
maintaining pages.
- Web modules
- A Web module represents a Web application. A Web module is created by
assembling servlets, JavaServer Pages (JSP) files, and static content such
as Hypertext Markup Language (HTML) pages into a single deployable unit. Web
modules are stored in Web archive (WAR) files, which are standard Java archive
files.
- Security constraints
- Security constraints determine how Web content is to be protected. These
properties associate security constraints with one or more Web resource collections.
A constraint consists of a Web resource collection, an authorization constraint
and a user data constraint.
- File serving
- File serving allows a Web application to serve static file types, such
as HTML. File-serving attributes are used by the servlet that implements file-serving
behavior.
- Sessions
- A session is a series of requests to a servlet, originating from the same
user at the same browser.
- Session management support
- WebSphere Application Server provides facilities, grouped under the heading
Session Management, that support the javax.servlet.http.HttpSession interface
described in the Servlet API specification.
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- The product provides database session persistence and memory-to-memory
session replication in a distributed environment.
- Base in-memory session pool size
- The base in-memory session pool size number has different meanings, depending
on session support configuration.