Spring Web Flow why ,what and how to make use of flow definitions , have big picture and full navigation control using Spring MVC framework

1. Introducing
Spring Web Flow
Emad Omara
1
May 30, 2016

2. Agenda
• Why do we need SWF ?
• What is SWF ?
• How it works ?
• Demo
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3. The Navigation problem !
 response.sendRedirect(“page.jsp");
 Spring MVC :
@RequestMapping("/operation")
public String processOperationPage() { return “/corpus/operation"; }
- Struts
<action-mappings> …. <forward name="name" path="/name.jsp"/> </ action-mappings>
- JSF
<navigation-rule><navigation-case>
<from-outcome>page2</from-outcome>
<to-view-id>/page2.xhtml</to-view-id>
</navigation-case> </navigation-rule> 3

4. Disadvantages
 Visualizing the flow is very difficult
 Mixed navigation and view
 Overall navigation rules complexity
 Lack of state control/navigation customization
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5. What is Spring Web Flow?
 Spring MVC extension
 Introduces flows concept
 Extends application scopes
 Web flows are designed to be self contained, and thus
are reusable multiple of times
 UML Like diagram 
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6. Important Classes
 FlowDefinition - This class stores the definition of the flow. It contains the set of states that form
part of the flow. Each flow has one start state.
 FlowRegistry - This class contains all the flow definitions.
 FlowHandlerMapping - This is a HandlerMapping that creates a URL from the ids registered in the
flow registry. It returns a FlowHandler if a matching id is found in the flow registry.
 FlowHandler - This is a controller helper that has the reference to the actual flow. It handles the
execution of the flow, its outcomes and exceptions.
 FlowHandlerAdapter - This is the HandlerAdapter for web flows. It delegates work to the mapped
FlowHandler.
 FlowExecutor - This is the central class of the Flow and is the facade for the actual flow. It manages
creating of new flows or resuming existing flows. It is an entry into the Spring web flow system.
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7. Request Diagram

8. System Setup
 Web Flow schema :
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:webflow="http://www.springframework.org/schema/webflow-config"
xsi:schemaLocation=" http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-config-2.4.xsd">
<!-- Setup Web Flow here -->
</beans>
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9. System Setup 2 (Flow Registry)
URL : /WEB-INF/flows/hotels/booking/booking-flow.xml
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Flow ID=/hotels/booking
Flow ID=springpizza
Flow ID=pizza

10. System Setup 3
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11. Flow
 A flow defines a dialogue, between users and server that meets business goal
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12. Flow Essential elements
 State
 Transition
 Flow data
 Expression language
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13. Flow States
 View States : A view state displays information to a user or obtains user input using a
form. (e.g. JSP)
 Action States : Action states are where actions are perfomed by the spring beans. The
action state transitions to another state. The action states generally have an evaluate
property that describes what needs to be done.
 Decision States: A decision state has two transitions depending on whether the
decision evaluates to true or false.
 Subflow States :It may be advantageous to call another flow from one flow to
complete some steps. Passing inputs and expecting outputs.
 End States : The end state signifies the end of flow. If the end state is part of a root flow
then the execution is ended. However, if its part of a sub flow then the root flow is resumed.
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14. Flow Data Scopes
 Flow Data can be stored as variables that can be created using the 'var' element.
 Variable scope - The lifespan of the variable depends on the scope with which it is declared. The
scopes available are:
 Request - Available during the life of a request in a flow
 Flash -Extended request scope for PRG case , Useful for rendering error/warning messages
 View - Available only during the lifetime of a view. Created when a view is created and destroyed once a
view is destroyed
 Flow - Available within a flow. Not available in sub flows
 Conversation - The conversation scope starts when a flow starts and ends when the flow ends. It is available
in sub flows
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15. Flow elements
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16. View State
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17. Decision State
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18. Action State
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19. Sub Flow State
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20. Input attributes
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21. Output Value
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22. Firing Events
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23. Events
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24. References
 Web Flow reference
 http://static.springframework.org/spring-webflow/docs/2.3.x/reference/html/index.html
 samples
 https://github.com/spring-projects/spring-webflow-samples
 Spring Web Flow 2 Web Development
 https://www.safaribooksonline.com/library/view/spring-web-flow/9781847195425/pr01.html
 Refcardz
 http://refcardz.dzone.com/refcardz/spring-web-flow
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25. Demo
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26. Thank you
Emad
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