SpringMVC

Copyright AlphaCSP Israel 2008 – Web Framework Playoff Seminar2

Spring MVCSpring MVC

Dror BereznitskySenior Consultant and

Architect, AlphaCSP

It’s TimeIt’s Time


AgendaAgenda

IntroductionBackgroundFeatures Review– Configuration– View technology– Page flow– Table sorting– Search results pagination– Validation– AJAX– Error handling– I18n– Documentation

Summary


IntroductionIntroduction

Spring’s web framework– Optional Spring framework component– Integrated with the Spring IoC container

Web MVC framework – Request-driven action framework– Designed around a central servlet– Easy for Struts users to adopt


Introduction::Introduction:: Key Features Key Features

Simple model– Easy to get going - fast learning curve Designed for extension– Smart extension points put you in control

Strong integration– Integrates popular view technologies

A part of the Spring framework– All artifacts are testable and benefit from

dependency injection


Introduction:: More Key FeaturesIntroduction:: More Key Features

Strong REST foundationsData Binding FrameworkValidation FrameworkInternationalization SupportTag Library


Introduction:: Full Stack Framework?Introduction:: Full Stack Framework?

Spring MVC is not a full-stack web framework, but provide the foundations for suchSpring MVC is not opinionated– You use the pieces you need– You adopt the pieces in piece-meal

fashion


Introduction:: Spring 2.5Introduction:: Spring 2.5

Released November 2007Simplified, annotation based model for developing Spring MVC applicationsLess XML than previous versionsFocuses on – ease of use– smart defaults– simplified programming model


AgendaAgenda


Summary


Background::Background:: Dispatcher Servlet Dispatcher Servlet

Dispatcher Servlet - front controller that coordinates the processing of all requests– Dispatches requests to handlers

– Issues appropriate responses to clients

Analogous to a Struts Action Servlet

Define one per logical web application


Background:: Request HandlersBackground:: Request Handlers

Incoming requests are dispatched to handlers– There are potentially many handlers per

Dispatcher Servlet– Controllers are request handlers


Background:: Background:: ModelAndViewModelAndView

Controllers return a result object called a ModelAndView– Selects the view to render the response– Contains the data needed for rendering

Model = contract between the Controller and the ViewThe same Controller often returns different ModelAndView objects– To render different types of responses


Background:: Request LifecycleBackground:: Request Lifecycle

Copyright 2006, www.springframework.org

Handler


Features ReviewFeatures Review


Summary


Features:: ConfigurationFeatures:: Configuration

Old school Spring beans XML configurationAnnotation based configuration for Controllers (v2.5)– XML configuration is still required for

more advanced features: interceptors, view resolver, etc.

– Not mandatory, everything can still be done with XML


Deploy a DispatcherServletDeploy a DispatcherServlet

Minimal web deployment descriptor

<servlet> <servlet-name>spring-mvc-demo</servlet-name> <servlet-class>

org.springframework.web.servlet.DispatcherServlet </servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value> /WEB-INF/spring-mvc-demo-servlet.xml </param-value> </init-param> </servlet>

Dispatcher servlet configuration

web.xmlweb.xml


Annotated ControllersAnnotated Controllers

Simple POJO – no need to extend any controller base class !

@Controller

public class PhoneBookController {

@RequestMapping(value = "/phoneBook", method = RequestMethod.GET)

protected ModelAndView setupForm() throws Exception {

ModelAndView mv = new ModelAndView();

…

return mv;

}

PhoneBookController.javaPhoneBookController.java


Dispatcher Servlet Dispatcher Servlet ConfigurationConfiguration

/WEB-INF/spring-mvc-demo.xml– Setting up the dispatcher for annotation support– Actually done by default for DispatcherServlet

– Auto detection for @Controller annotated beans

<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"/>

<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>

<context:component-scan base-package="com.alphacsp.webFrameworksPlayoff"/>


Supported out of the box:– JSP / JSTL– XML / XSLT– Apache Velocity– Freemarker– Adobe PDF– Microsoft Excel– Jasper Reports

Features:: View TechnologyFeatures:: View Technology


Configure the view technologyConfigure the view technology

View Resolvers – Renders the model– Decoupling the view technology JSTL view– JSP + JSTL –native choice for Spring MVC– Spring tag libraries

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view. JstlView “ /> <property name="prefix" value="/WEB-INF/views"/> <property name="suffix" value=".jsp"/></bean>


Features:: Page FlowFeatures:: Page Flow

mv.setView(new RedirectView( "../phoneBook“ , true));


Features:: Page Flow – Step 1Features:: Page Flow – Step 1

Mapping URLs to handler methods– Method level annotations– Can restrict to specific request method– URL strings can be error prone !

@RequestMapping(value = "/phoneBook", method = RequestMethod.GET) protected ModelAndView setupForm() throws Exception { ModelAndView mv = new ModelAndView(); mv.addObject("contacts", Collections.<Contact>emptyList()); mv.addObject("contact", new Contact()); … }

PhoneBookController.javaPhoneBookController.java


Page Flow – Step 1 Contd.Page Flow – Step 1 Contd.

DispatcherServlet PhoneBookController

Handle GET /demo/phoneBook

1

InternalResourceViewResolver

2 phoneBook /WEB-INF/views/phoneBook.jsp

phoneBook


Page Flow – Step 2Page Flow – Step 2

Choosing the view to be rendered– Set the ModelAndView view name

– Or just return a view name String

@RequestMapping(value = "/phoneBook", method = RequestMethod.GET)protected ModelAndView setupForm() throws Exception {

ModelAndView mv = new ModelAndView();mv.setViewName("phoneBook");return mv; PhoneBookController.javaPhoneBookController.java

@RequestMapping(value = "/phoneBook", method = RequestMethod.GET)protected ModelAndView setupForm() throws Exception { return " phoneBook "; }


Page Flow – Step 2 Contd.Page Flow – Step 2 Contd.

DispatcherServlet PhoneBookController

Handle GET /demo/phoneBook

1

InternalResourceViewResolver

2 phoneBook /WEB-INF/views/phoneBook.jsp

phoneBook


Features:: Sorting & PaginationFeatures:: Sorting & Pagination

Search results paginationSearch results pagination

Sorting by columnSorting by column


Features:: Table SortingFeatures:: Table Sorting

Used the display tag library– Handles column display, sorting, paging,

cropping, grouping, exporting, and more– Supports internal and external sorting– Sort only visible records or the entire list

<%@ taglib uri="http://displaytag.sf.net" prefix="display" %>

<display:table name="contacts" class="grid" id="contacts" sort="list" pagesize="5" requestURI="/demo/phoneBook/list"> <display:column property="fullName" title="Name" class="grid" headerClass="grid" sortable="true"/> …</display:table> phoneBook.jspphoneBook.jsp


Features:: Search Results PaginationFeatures:: Search Results Pagination

Used the display tag pagination support for the demo– Supports internal and external

pagination– Adds pagination parameter to request– Limited to HTTP GET


Features:: Form BindingFeatures:: Form Binding

@ModelAttribute annotations

Spring’s form tag library– EL expressions for binding path

<td class="searchLabel"><b><label for="email">Email</label></b></td><td class="search"> <form:input id="email“ path="email" tabindex="2" /></td>

@RequestMapping(value = "/phoneBook/list")

protected ModelAndView onSubmit(

@ModelAttribute("contact") Contact contact, BindingResult result)


Features:: ValidationsFeatures:: Validations

Used Spring Modules bean validation framework for server side validation– Clear separation of concerns– Declarative validation as in commons-

validation– Supports Valang - extensible expression

language for validation rules


Bean Validation ConfigurationBean Validation Configuration

Load validation XML configuration file [1]Create a bean validator [2]

<bean id="configurationLoader"

class="DefaultXmlBeanValidationConfigurationLoader">

<property name="resource" value="WEB-INF/validation.xml" />

</bean>

<bean id="beanValidator"

class="org.springmodules.validation.bean.BeanValidator">

<property name="configurationLoader" ref="configurationLoader" />

</bean>

1

2


<validation>

<class name="com.alphacsp.webFrameworksPlayoff. Contact "> <property name="email"> <email message="Please enter a valid email address"

apply-if="email IS NOT BLANK"/> </property> </class>

</validation>

Domain Model

Domain Model

Bean Validation ConfigurationBean Validation Configuration

Contact email validation– Bound to the domain model and not to a

specific form

Validation.xmlValidation.xml


Server Side ValidationsServer Side Validations

Validator is injected to the controllerReusing the binding errors object

@Autowired Validator validator;

@RequestMapping(value = "/phoneBook/list") protected ModelAndView onSubmit(@ModelAttribute("contact") Contact

contact, BindingResult result) throws Exception { … validator.validate(contact, result); … PhoneBookController.javaPhoneBookController.java


Client Side ValidationClient Side Validation

Valang validator – validation is defined in valang

expression language

<bean id="clientSideValidator"class="org.springmodules.validation.valang.ValangValidator">

<property name="valang"> <value> <![CDATA[ { firstName : ? IS NOT BLANK OR department IS NOT BLANK

OR email IS NOT BLANK : 'At least one field is required'} ]]> </value> </property></bean>


<%@ taglib uri="http://www.springmodules.org/tags/valang" prefix="valang" %>

<script type="text/javascript" src="/scripts/valang_codebase.js"></script>

<form:form method="POST" action="/demo/phoneBook/list" id="contact" name="contact" commandName="contact" >

<valang:validate commandName="contact" />

Client Side Validation Contd.Client Side Validation Contd.

Use Valang tag library to apply the valang validator at client side– Validation expression is translated to

JavaScript<script type="text/javascript" id="contactValangValidator">

new ValangValidator('contact',true,new Array(

new ValangValidator.Rule('firstName','not implemented', 'At least one field is required',function() {

return ((! this.isBlank((this.getPropertyValue('firstName')), (null))) || (! this.isBlank((this.getPropertyValue('department')), (null)))) || (! this.isBlank((this.getPropertyValue('email')), (null)))})))

</script>

<script type="text/javascript" id="contactValangValidator">

new ValangValidator('contact',true,new Array(

new ValangValidator.Rule('firstName','not implemented', 'At least one field is required',function() {

return ((! this.isBlank((this.getPropertyValue('firstName')), (null))) || (! this.isBlank((this.getPropertyValue('department')), (null)))) || (! this.isBlank((this.getPropertyValue('email')), (null)))})))

</script>

phoneBook.jspphoneBook.jsp


Features:: AJAXFeatures:: AJAX

No built in AJAX support– DWR is unofficially

recommended by Spring

Used DWR to expose the department service to JavaScript– Requires dealing for low-level AJAX– DWR has simple integration with Spring

Used script.aculo.us autocomplete component with DWR


AJAX:: ConfigurationAJAX:: Configuration

The department service Spring bean

<dwr> <allow> <create creator="spring" javascript="DepartmentServiceFacade"> <param name="beanName" value="departmentServiceFacade"/> </create> </allow></dwr>

<bean id="departmentServiceFacade" class="com.alphacsp.webFrameworksPlayoff.service.impl.

MockRemoteDepartmentServiceImpl“ />

Exposing it to JavaScript using DWRDWR.xmlDWR.xml


AJAX:: Autocomplete ComponentAJAX:: Autocomplete Component

<script type="text/javascript" src="/scripts/prototype/prototype.js"></script><script type="text/javascript" src="/scripts/script.aculo.us/controls.js"></script><script type="text/javascript" src="/scripts/autocomplete.js"></script>

<td class="search"> <form:input id="department" path="department" tabindex="3" cssClass="searchField"/> <div id="departmentList" class="auto_complete"></div> <script type="text/javascript">

new Autocompleter.DWR('department', 'departmentList', updateList, {valueSelector: nameValueSelector, partialChars: 0 });

</script></td>

phoneBook.jspphoneBook.jsp


Features:: Error HandlingFeatures:: Error Handling

HandlerExceptionResolvers - handle unexpected exceptions– Programmatic exception handling– Information about what handler was

executing when the exception was thrown

– SimpleMappingExceptionResolver – map exception classes to views


Features:: I18nFeatures:: I18n

LocaleResolver – automatically resolve messages

using the client's locale • AcceptHeaderLocaleResolver• CookieLocaleResolver• SessionLocaleResolver

LocaleChangeInterceptor– change the locale in specific cases

Reloadable resource bundles


Features:: DocumentationFeatures:: Documentation

Excellent reference documentation !Books – mostly on the entire frameworkCode samplesMany AppFuse QuickStart applications


SummarySummary


Summary


Summary:: ProsSummary:: Pros

Pros:– Highly flexible– Strong REST foundations – A wide choice of view technologies– New annotation configuration,

less XML, more defaults– Integrates with many common web

solutions– Easy adoption for Struts 1 users


Summary:: ConsSummary:: Cons

Cons:– Model2 MVC forces you to build

your application around request/response principles as dictated by HTTPThis was done by design in Spring MVC

– Requires a lot of work in the presentation layer: JSP, Javascript, etc.

– No AJAX support out of the box– No components support


Summary:: RoadmapSummary:: Roadmap

Spring 3.0 – August/September 2008– Unification in the programming model

between Spring Web Flow and Spring MVC• SpringFaces - JSF Integration• Spring JavaScript - abstraction over common

JavaScript toolkits• AJAX support• Conversational state


Summary:: ReferencesSummary:: References

http://springframework.org/Spring SourceSpring ModulesSpring IDEAppfuse light - spring MVC quickstartsMatt Raible - Spring MVCExpert Spring MVC and Web Flow


Thank Thank You !You !

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