Programming Thoughts
Struts 2 - Pagination
Different Interceptor Stacks
Obvious but not part of the default
Those who've come this far have already noticed at least two roles for Actions: processing forms and
displaying data. The officially recommended Post/Redirect/Get practically forces this. Yet the Struts 2
baseline struts-default.xml
only expects defaultStack as the interceptor stack to be generally used. This article will examine
one for each role.
Custom interceptors
The configuration fragments in this article refers to custom interceptors. The description for each is below.
| Name | Purpose | Description |
|---|---|---|
formRetrieve |
Retrieve a stored form from session for display. | Preserving forms and More Form Injection |
formStore |
Store a processed form into session so it's preserved in a redirect. | Preserving forms and More Form Injection |
messageAmalgamation |
Copy messages from previous Actions to the last when dispatching from one to another. | Alternate solution |
messageRetrieve |
Retrieve stored messages from session for display. | Preserving user messages |
messageStore |
Store messages into session so it's preserved in a redirect. | Preserving user messages |
Abstract interceptor stacks
Interceptor stacks can contain other interceptor stacks and the custom stacks in later sections contain the ones below. They're based on the default stack and refer to the built-in interceptors.
<interceptor-stack name="CommonStackTop"> </interceptor-stack> <!-- This is the default stack minus the exception, validation and workflow interceptor --> <interceptor-stack name="CommonStackBottom"> <interceptor-ref name="alias"/> <interceptor-ref name="servletConfig"/> <interceptor-ref name="i18n"/> <interceptor-ref name="prepare"/> <interceptor-ref name="chain"/> <interceptor-ref name="debugging"/> <interceptor-ref name="scopedModelDriven"/> <interceptor-ref name="modelDriven"/> <interceptor-ref name="fileUpload"/> <interceptor-ref name="checkbox"/> <interceptor-ref name="multiselect"/> <interceptor-ref name="staticParams"/> <interceptor-ref name="actionMappingParams"/> <interceptor-ref name="params"> <param name="excludeParams">dojo\..*,^struts\..*</param> </interceptor-ref> <interceptor-ref name="conversionError"/> </interceptor-stack>
Viewer interceptor stacks
Viewer Actions should be concerned with retrieving data for display in its JSP page and dispatching to that
JSP, not processing a job and deciding the next step. This includes forms and messages stored across a redirect
whilst validator and worflow interceptors can be skipped. The interceptor stack is
shown below.
<interceptor-stack name="ViewStack"> <interceptor-ref name="CommonStackTop" /> <interceptor-ref name="formRetrieve" /> <interceptor-ref name="messageRetrieve" /> <interceptor-ref name="messageAmalgamation" /> <interceptor-ref name="CommonStackBottom" /> </interceptor-stack>
Form processing interceptor stacks
Form processing Actions process a task and redirects to a viewer Action to display results. The interceptor stack is shown below.
<interceptor-stack name="FormDrivenStack"> <interceptor-ref name="CommonStackTop" /> <interceptor-ref name="formStore" /> <interceptor-ref name="messageStore" /> <interceptor-ref name="CommonStackBottom" /> <interceptor-ref name="validation"> <param name="excludeMethods">input,back,cancel,browse</param> </interceptor-ref> <interceptor-ref name="workflow"> <param name="excludeMethods">input,back,cancel,browse</param> </interceptor-ref> </interceptor-stack>
Next part
Continued in Example.