Spring MVC

From Kb

Jump to: navigation, search

Contact Article Author | Blog of Article Author | FirstPartners.net Home | LinkedIn profile of Author

Contents

See also

External Documentation on the Spring MVC (Model View Controller) Web Framework

Flow of control in Spring Web app

  1. User makes request to [myserver]/[myapp]/somepage.htm
  2. web.xml maps this to (one of) the Spring dispatcher servlets
  3. This looks up the url in the Spring app context (e.g. springApp-servlet.xml)
  4. Normally have a urlMapping bean (e.g. Spring SimpleUrlHandlerMapping implements HandlerMapping) that says which Spring bean is called
  5. Spring bean implements Controller has method public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
    1. Spring controller akin to Struts Action class.
  6. handleRequest method called, does it's stuff , returns ModelAndView class
  7. Within Spring file , instance of ViewResolver (e.g. ResourceBundleViewResolver - uses property file to resolve to class) is configured - maps to the bean which Tells Spring what / how to find the view.
    1. If forward to JSP use (as simple example) InternalResourceViewResolver - takes name in ModelAndView class and adds (configurable) prefix / suffix to come up with jsp name to display.
    2. Other ViewResolvers available
  8. Can display view via JSP (e.g. as per Struts) , or completely in Java Code within the Spring view bean (e.g. like traditional Servlets)
    1. JSP uses {beanName.internalBean.method} type syntax to display results from the model
    2. Can manipulate these values using standard JSTL Tags.
    3. Spring tagLib provides access to other Spring values (sample on page 315 of manning book)

Spring Tag Libraries

Spring form: Tag Library

  • Bundled with Spring 2
  • Spring Tags Reference
  • To install
    • Make sure tld definition is included in web.xml
    • reference tag at top of your jsp page
    • (Here spring core, spring core and standard JSTL tags are imported) 
<!-- Standard Spring tags -->
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
 
<!-- Spring tags to bind objects to HTML input / output values -->
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
 
<!-- Standard JSTL taglib -->
<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core_rt"%>


<!-- Spring MVC tag for form - commandName is the Spring Bean that the values will be bound to-->
<!-- 'name' (myForm) is what it will be rendered as in HTML i.e. if we want to refer to values in Javascript we go Document.myForm.submit() -->
<form:form commandName="mySpringBeanName" name="myForm" method="post">
 
 
<!-- Other Fields-->
<!-- Path refers to some bean available in the Session / Flow. It does not include the form bean (as it is defined by the form tag). The samples below would ties to myFormBean.getNameOfVarOnMySpringBean().getValueWithGetAndSetMethodsOnVar() etc -->
<form:label id='someLabel' path="nameOfVarOnMySpringBean.someSubGetMethod"/>
<form:input id='someInput' path="nameOfVarOnMySpringBean.valueWithGetAndSetMethodsOnVar"/>
 
<!-- IMPORTANT note that for JSTL TAGS myBeanName must be added to the path -->
<!-- You need to use JSTL as Spring does not supply a simple text output method-->
<c:out value="${myFormBean.nameOfVarOnMySpringBean.someSubGetMethod}"/>
 
<!-- Button to submit form -->
<input type="submit" value="OK" />
 
</form:form>

Java Standard Tag Library (JSTL) 

<c:forEach items="${myFormBean.customerList}" var="cust" varStatus="status">
            <c:out value="${customerList.customerName}" />
	    <form:checkbox path="customerList[${status.index}].customerPremiumPaid"/>
 
	</c:forEach>

Spring MVC and Apache Tiles

General

Apache Tiles Integration with Spring MVC

  • org.springframework.web.servlet.view.tiles.TilesConfigurer
    • Loads Tiles Configuration as part of Spring Context (means that we don't need to load the Tiles Servlet (via the Web.xml) , which would normally do this.
  • Use of a custom Spring View Resolver (extending Springs AbstractCachingViewResolver). org.springframework.web.servlet.view.tiles.TilesView is the Spring View that allows Spring to pass control to tiles.
  • Flow of control is as per Section above; when the time comes to display a view, The program resolves to Tiles , which then does it's stuff.

Alternative Views

AbstractXsltView

Spring MVC and Spring Webflow

  • Entry point from MVC to Webflow:
    • Url (e.g. /webflow) is mapped in SpringContext file (name of context file is related to name of Servlet). Spring looks up the bean associate with this. For Webflow , this is an instance of the org.springframework.webflow.executor.mvc.FlowController, takes another bean as a param
      • flow:executor - refers (using shortcuts) to the registry
      • flow:registry - refers (using shortcuts) to the Spring Webflow config files
  • Exit point from Webflow to MVC:
    • The output of the Webflow is always a view state. This viewState is bound to a SpringViewResolver to that Spring MVC knows what page / view to display once the flow enters a wait state.

Comparing Spring MVC to Struts and Struts 2

  • Both implementations on Model View Controller
  • Spring controller akin to Struts 2Action class. Both POJO's , unlike Struts 2.
  • Config done in standard Spring context, using Standard beans. Struts (2) has Struts(-config).xml , carries out most of the URL -> Bean -> view mapping functionality.
  • (Slightly) easier to unit test Spring MVC, use Standard Spring unit testing tools. Would tend to test Struts + Spring combo at the Spring level anyway.
  • Possibility of using Spring ThrowawayController - similar to Struts 2 Action + ActionForm combo.
Retrieved from "http://www.firstpartners.net/kb/index.php/Spring_MVC"
Personal tools