EGL Reference Guide for iSeries
This section gives a technical overview of the run-time interaction of user
and Web application server.
When the user invokes a JSP that is supported by a page handler, the
following steps occur:
- The Web application server initializes the environment--
- Constructs a session object to retain data that the user-accessed
applications need across multiple interactions
- Constructs a request object to retain data on the user's current
interaction
- Invokes the JSP
- The JSP processes a series of JSF tags to construct a Web page--
- Creates an instance of the page handler, causes the onPageLoad function
(if any) to be invoked with user-specified arguments, and places the page
handler into the request object
- Accesses data stored in the request and session objects, for inclusion in
the Web page
- Note:
- The pageHandler part has a property called OnPageLoad, which identifies the
page-handler function that is invoked at JSP startup. The function
automatically retrieves any user-supplied arguments that were passed to
it; can call other code; and can place additional data in the
request or session object of the Web application server; but the function
can neither forward control to another page nor cause an error message to be
displayed when the page is first presented to the user.
- The JSP submits the Web page to the user, and the Web application server
destroys the response object, leaving the session object and the JSP.
If the user supplies data in the on-screen fields associated with an HTML
<FORM> tag and submits the form, the following steps occur:
- The Web application server re-initializes the environment--
- Constructs a request object
- Places the received data for the submitted form into the page bean, for
validation
- Re-invokes the JSP
- The JSP processes a series of JSF tags to store the received data in the
page bean.
- The run-time page handler validates data:
- Does relatively elementary edits (such as minimum input length), as
specified in the pageHandler data declarations
- Invokes any item-specific validation functions, as specified in the
pageHandler data declarations
- Invokes a pageHandler validator function, as is needed if you wish to
validate one field at least partially on the basis of the content of another
field
(For details on validation, see the previous section.)
- If an error occurs, the EGL run time places errors on a JSF queue, and the
JSP re-displays the Web page with embedded messages. If no error
occurs, however, the result is as follows:
- Data stored in the page bean is written to the record bean
- Subsequent processing is determined by an event handler, which is
identified in the JSF tag that is associated with the user-clicked button or
hyperlink.
The event handler may forward processing to a JSF label, which identifies a
mapping in a run-time JSF-based configuration file. The mapping in turn
identifies the object to invoke, whether a JSP (usually one associated with an
EGL page handler) or a servlet.
Related concepts
References to parts
Web support
Related reference
Page Designer support for EGL
PageHandler part in EGL source format
Page item properties
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