This document discusses Struts 2 architecture and concepts including: 1. Action mapping is used to map URLs and parameters to actions and methods through configuration. 2. The action context and OGNL context provide access to request parameters, session attributes, and other objects through the value stack. 3. Interceptors perform common tasks before and after actions and can prepare parameters and handle exceptions. 4. Result types help produce different response content types like JSON or page redirects by preparing models for templates. 5. Configuration, initialization, and the filter process set up Struts 2 and handle request processing and routing to actions.

1. Thomas Tu
thomas.tu@ehealth-china.com

2. Agenda
 Struts 2 Architecture & Request Processing
 Action Mapping
 Action Context & Data Binding
 Interceptors
 Result Types
 Initialization & Configuration
 Struts 2 in EHI Software Architecture

3. *1 action mapping
*2 interceptors
*3 action & result
1
2
3
ActionContext

4. Agenda
 Struts 2 Architecture & Request Processing
 Action Mapping
 Action Context & Data Binding
 Interceptors
 Result Types
 Initialization & Configuration
 Struts 2 in EHI Software Architecture

5. Action Mapping – find the right action/method
Task: url + parameters  namespace, action, method
 How to do?
 namespace: url
 actionName: url < special
parameter
 methodName: special
parameter < dynamic
method, config < default
Related codes:
DefaultActionMapper.java
ActionMapping mapping = new ActionMapping();
……
parseNameAndNamespace(uri, mapping, configMan
ager);
handleSpecialParameters(request, mapping);
if (mapping.getName() == null) {
return null;
}
parseActionName(mapping);
return mapping;

6. Agenda
 Struts 2 Architecture & Request Processing
 Action Mapping
 Action Context & Data Binding
 Interceptors
 Result Types
 Initialization & Configuration
 Struts 2 in EHI Software Architecture

7. OGNL Context (ActionContext)
OGNL
Action Context
Value Stack (OGNL root)
|___Action
|___other objects…
#parameters
#request
#session
#application
#attr (searches p, r, s, then a)

8. Data Binding & Type Conversion
Based on OGNL, struts 2 support data binding and accessing as
follows:
From request to action model:
census.zipCode=90001  action. getCensus(). setZipCode(“90001”)
census.requestEffectiveDate=5/1/2011  action. getCensus().
setRequestEffectiveDate(..)
From action context to template (freemarker):
${plan.officeVisitText}  productView.getOfficeVisitText()
${plan.pastRate?string("$#,##0.00")} 
formatter.format(productView.getPastRate(), "$#,##0.00")

9. Agenda
 Struts 2 Architecture & Request Processing
 Action Mapping
 Action Context & Data Binding
 Interceptors
 Result Types
 Initialization & Configuration
 Struts 2 in EHI Software Architecture

10. Interceptors
request
– do common jobs before or after
exceptionInterceptor
… loginInterceptor
… sessionValidator
…
action
result
response
error output

11. Interceptors in EHI
from struts.xml
<interceptor-stack name="defaultStack">
<interceptor-ref name="exception">
<param name="logEnabled">true</param>
<param name="logLevel">WARN</param>
</interceptor-ref>
<interceptor-ref name="servletConfig"/>
<interceptor-ref name="staticParams"/>
<interceptor-ref name="setupContexts"/>
<interceptor-ref name="https"/>
<interceptor-ref name="sessionTimeout"/>
<interceptor-ref name="login"/>
<interceptor-ref name="alliance"/>
<interceptor-ref name="ehiServlet"/>
<interceptor-ref name="webAppContext"/>
<interceptor-ref name="checkbox"/>
<interceptor-ref name="params"/>
<interceptor-ref name="sessionValidator"/>
<interceptor-ref name="prepare"/>
<interceptor-ref
name="changeSessionInactiveInterval"/>
<interceptor-ref name="chain"/>
<interceptor-ref name="validation">
<param name="excludeMethods">input,back,cancel</param>
</interceptor-ref>
<interceptor-ref name="workflow">
<param name="excludeMethods">input,back,cancel</param>
</interceptor-ref>
<interceptor-ref name="ab"/>
<interceptor-ref name="tracking"/>
</interceptor-stack>

12. Q: why struts 2 action needn’t be required to
implement any interface?
 Why need a interface?
 Because it can help core controller to find: action
method name and its parameter requirements
 Action method was invoked by reflection, so it can be
any method name
 Interceptors can help prepare any parameters declared
by action class

13. Agenda
 Struts 2 Architecture & Request Processing
 Action Mapping
 Action Context & Data Binding
 Interceptors
 Result Types
 Initialization & Configuration
 Struts 2 in EHI Software Architecture

14. Result Types – help produce response content
Q: How struts 2 to support multiple result types?
 How to produce response content?
 Model + template = content (json, redirect)
 Result type can help prepare the required model

15. Agenda
 Struts 2 Architecture & Request Processing
 Action Mapping
 Action Context & Data Binding
 Interceptors
 Result Types
 Initialization & Configuration
 Struts 2 in EHI Software Architecture

16. Configuration
In struts-default.xml:
<bean class="com.opensymphony.xwork2.ObjectFactory" name="xwork" />
<bean type="com.opensymphony.xwork2.ObjectFactory" name="struts" class=“…”/>
<bean type="com.opensymphony.xwork2.ActionProxyFactory" name="xwork" class=“…"/>
<bean type="com.opensymphony.xwork2.ActionProxyFactory" name="struts" class=“…"/>
In struts-plugin.xml (spring plugin):
<bean type="com.opensymphony.xwork2.ObjectFactory" name="spring"
class="org.apache.struts2.spring.StrutsSpringObjectFactory" />
In struts.xml
<constant name="struts.ui.templateDir" value="/WEB-INF/tags"/>
<constant name="struts.ui.theme" value="simple"/>
<constant name="struts.objectFactory" value="spring"/>
<constant name="struts.action.extension" value=""/>
<constant name="struts.mapper.class" value="com.ehi.struts.core.ActionMapper"/>
In struts/xwork codes:
@Inject
public void setContainer(Container container) {
…
@Inject(StrutsConstants.STRUTS_ACTION_EXTENSION)
public void setExtensions(String extensions) {

17. Initialization
In web.xml:
<filter>
<filter-name>struts</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>
When starting app server:
StrutsPrepareAndExecuteFilter  Dispatcher.init()
When incoming request (in StrutsPrepareAndExecuteFilter.doFilter(req, resp) ):
prepare.setEncodingAndLocale(request, response);
prepare.createActionContext(request, response);
prepare.assignDispatcherToThread();
if ( excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) {
chain.doFilter(request, response);
} else {
request = prepare.wrapRequest(request);
ActionMapping mapping = prepare.findActionMapping(request, response, true);
if (mapping == null) {
boolean handled = execute.executeStaticResourceRequest(request, response);
if (!handled) {
chain.doFilter(request, response);
}
} else {
execute.executeAction(request, response, mapping);
}
}

18. Agenda
 Struts 2 Architecture & Request Processing
 Action Mapping
 Action Context & Data Binding
 Interceptors
 Result Types
 Initialization & Configuration
 Struts 2 in EHI Software Architecture

19. Struts 2 in EHI Software Architecture
freemarker
jsp
template
template
template
page page
Struts 2
action
action
action
spring
Business
Object
Business
Object
action
screen
screen screen
Helper
Helper
Helper
Business
Object
db
EHIDataBase
resources
Business
Business
Object
Object

20. Thanks!