To execute Web applications in Application Server, the servlets and JSPs that are compliant with the version of the Web application defined in web.xml are executed.

The version setup functionality of Web applications is used for specifying versions, when executing Web applications. You can use this functionality to execute the Web application compliant with the specified version without changing the version of the Web application defined in web.xml.

The following are the differences when you use or do not use the version setup functionality of Web applications:

When using the version setup functionality of Web applications

You need not change the version of the Web application defined in web.xml to execute servlets and JSPs compliant with the new version, for executing the Web application created in the earlier version.

If version of the Web application to be executed is specified, a syntax check in JSP compilation and operations of servlet APIs are changed simultaneously, when you change web.xml. However, you cannot use the functions that must be defined in web.xml.

When the version setup functionality of Web applications is not used

For executing the Web application created in earlier version, you must change the version of the Web application defined in web.xml to execute servlets and JSPs compliant with the new version.

The following table describes the different operations of Web applications that are defined in web.xml, depending on the version specified by the version setup functionality of Web applications:

Table 2-68 Different operations depending on the version specified by the version setup functionality of Web applications

Version defined in web.xml	Version specified by the version setup functionality of Web applications
	No specifications	2.4	2.5
2.2	Operating as 2.3#1	Operating as 2.4	Operating as 2.5
2.3	Operating as 2.3
2.4	Operating as 2.4
2.5, 3.0	Operating as 2.5	Operating as 2.5#2

#1

When the version defined in web.xml is 2.2 and nothing is set up by the version setup functionality of Web applications, the operations are performed as the Web application of 2.3 version.

#2

When the version defined in web.xml is 2.5 and 2.4 version is set up by the version setup functionality of Web applications, the operations are performed as the Web application of 2.5 version.

Note

The version setup functionality of Web applications is used to support the migration of applications of the old version. We do not recommend using this functionality for developing new applications.

To develop a new application, specify the web.xml of the correct version.