Spring Web MVC

Spring Web
MVC
By: Zeeshan Hanif
Sr. Software Engineer
Etilize Pvt. Ltd.
A GfK Product data company

Agenda
 What is spring MVC
 Features
 Spring MVC Workflow
 Important Components of Spring MVC
 Demo – External configuration
 Demo – Annotation
 Convention over Configuration
 World without Rules
 Demo – Form Submission
 Demo – Session Storage
 Demo – REST based URL
 Demo – Ajax

Prerequisite
 Spring Core
 IOC & Dependency Injection

Spring MVC
 The Spring Web MVC Framework is a
robust, flexible, and well-designed
framework for rapidly developing web
applications using the MVC design
pattern.

Features
 Clear separation of roles. Each role —
controller, validator, command object,
form object, model object, handler
mapping, view resolver and so on.
 Powerful and straightforward
configuration of both framework and
application classes as JavaBeans
 Adaptability and flexibility. Define any
controller method signature you need for
a given scenario

Features (cont.)
 Use existing business objects as command
or form objects instead of mirroring them
to extend a particular framework base
class
 Flexible model transfer. Model transfer
with a name/value Map supports easy
integration with any view technology
 A simple yet powerful JSP tag library
 Easier testing
 REST based URL support

Spring MVC Workflow
Source: www.springsource.org

Important Components
 DispatcherServlet
 Controller
 HandlerMapping/@RequestMapping
 ModelAndView
 Model & @ModelAttribute
 ViewResolver

DispatcherServlet
 The Dispatcher Servlet follows the Front
Controller Design Pattern for handling
Client Requests.
 It means that whatever Url comes from
the Client, this Servlet will intercept the
Client Request before passing the
Request Object to the Controller.

DispatcherServlet (cont.)
<web-app>
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>*.gfk</url-pattern>
</servlet-mapping>
</web-app>

Controller
 Controllers are components that are
being called by the Dispatcher Servlet for
doing any kind of Business Logic
 Spring Distribution already comes with a
variety of Controller Components each
doing a specific purpose - spring 2.x
 SimpleFormController
 AbstractController
 MultiActionController
 Spring 3 Controller
 @Controller Annotation

Controller (Cont.)
 Old School of Spring MVC
public class MySimpleController extends AbstractController
{
public ModelAndView handleRequestInternal
(HttpServletRequest request,
HttpServletResponse response)
{
return new ModelAndView("myView");
}
}

Controller (Cont.)
 Spring MVC 3.0
@Controller
public class DemoSpring3Controller {
@RequestMapping("/demoSpring3")
public ModelAndView helloWorld() {
String msg = "Hello Spring 3 World! Etilize -- GfK";
return new ModelAndView("demosp",
"message", msg);
}
}
<context:component-scan base-package="com.gfk.etilize.controller" />

HandlerMapping
 A Handler Mapping provides an abstract
way that tell how the Client's Url has to be
mapped to the Handlers.
 Four concrete variation of Handler
Mapping are available
 BeanNameUrl HandlerMapping
 CommonsPathMap HandlerMapping
 ControllerClassName HandlerMapping
 SimpleUrl HandlerMapping

HandlerMapping (Cont.)
 BeanNameUrl HandlerMapping
 URL request
http://localhost:8080/spweb/showStudents
 Bean Mapping
<beans>
<bean id="beanNameUrl"
class="org.springframework.web.servlet.handler.
BeanNameUrlHandlerMapping"/>
<bean name="/showStudents.jsp"
class="com.gfk.etilize.ShowStudentsController">
</bean>
</beans>

 SimpleUrlHandlerMapping
<bean id="urlMapping"
class="org.springframework.web.servlet.handler.SimpleUrlHan
dlerMapping">
<property name="urlMap">
<map>
<entry key="/demoSpring.gfk">
<ref bean="demoSpringController"/>
</entry>
</map>
</property>
</bean>
<bean id="demoSpringController"
class="com.gfk.etilize.controller.DemoSpringController" />

 Spring 3.0 uses @RequestMapping for
Mapping
@Controller
public ModelAndView helloWorld() {
String msg = "Hello Spring 3 World";
return new ModelAndView("demosp",
"message", msg);
}
}

ModelAndView
 ModelandView is returned by the
Controller object back to the Dispatcher
Servlet.
 This class is just a Container class for
holding the Model and the View
information.
 This way of specifying a View is called a
Logical View. It means that demosp either
can point to something called demosp.jsp
or demosp.pdf or demosp.xml
ModelAndView(viewName, “Key”, object);
return new ModelAndView("demosp", "message", msg);

Model & @ModelAttribute
 Model object Automatically created on
every request
@RequestMapping
public void showList(Model model){
model.addAttribute("studentList",
studentService.getAllStudents());
}
Implicitly added to Model and can be accessed with key
“student”
@RequestMapping
public Student showList(){
return studentService.getStudent();
}

Model & @ModelAttribute
@ModelAttribute – customized name
@RequestMapping
public @ModelAttribute(“stu”) Student showList(){
return studentService.getStudent();
}
@ModelAttribute – Form values
@RequestMapping("/new")
public ModelAndView getStudentForm(){
return new ModelAndView("studentForm","student",new Student());
}
<form:form action="add.gfk" method="POST" commandName=" student " >
Name:<form:input path="name" size="60" /><br>
<input type="submit" value="Register" /></td>
</form:form>
@RequestMapping
public void saveStudent(@ModelAttribute Student stu){
studentService.saveStudent(stu);
}

View Resolver
 The mapping between the Logical name
and the Physical View Location is taken
care by the View Resolver object.
 Spring comes with a set of Built-In Spring
Resolvers.
 We can write Custom View Resolvers by
implementing the
org.springframework.web.servlet.ViewResolver
interface

View Resolver (Cont.)
 BeanNameViewResolver
 FreeMarkerViewResolver
 InternalResourceViewResolver
 JasperReportsViewResolver
 ResourceBundleViewResolver
 UrlBasedViewResolver
 VelocityLayoutViewResolver
 VelocityViewResolver
 XmlViewResolver
 XsltViewResolver

 InternalResourceViewResolver
Controller returns - new ModelAndView("myView1")
<bean id="viewResolver“
class="org.springframework.web.servlet.view.InternalResourceVie
wResolver">
<property name="prefix">
<value>/WEB-INF/</value>
</property>
<property name="suffix">
<value>.jsp</value>
</property>
</bean>
the prefix + the logical View Name + the suffix
/WEB-INF/myView.jsp

 BeanNameViewResolver
 One of the dis-advantage of
using InternalResourceViewResolver is that
the name of the View file (jsp or pdf) must
be present in the Web Application Context.
 Dynamically generated View files may not
be possible.
 In such a case, we may use the BeanName
ViewResolver which will dynamically
generate View in Pdf or Excel Formats.

Controller returns - new ModelAndView(“excel")
<bean id="beanNameResolver"
class="org.springframework.web.servlet.view.BeanNameViewReso
lver"/>
<bean id = “excel" class = "MyExcelGenerator"/>

Demo – External configuration
Demo – Annotation

Convention over Configuration
 Write less code, get consistency
 Conventions available for
 Request mapping
 View name selection
 Model population

 Mapping By RequestMapping
@Controller
public void helloWorld(){}
}

@Controller
public class StudentController {
@RequestMapping
public void listAll(Model model){
model.addAttribute(new Student("Test",23));
}
}
GET /student/listAll
Mapping of class and
method name
View with method name
selected from request path
Model key generated from object type

 Mapping By Convention
@Controller
public class StudentController {
URL  /student/showList , View  showList.jsp
@RequestMapping
public void showList(Model model){}
URL  /student/getStudent, View  getStudent.jsp
@RequestMapping
public Student getStudent(){
…
return stu;
}
}

World without Rules
 Return Type?
 Return Type Can be:
 ModelAndViewObject
 Model
 Map
 View
 String
 Void
 Any Custom or built-in datatype
 e.g. Student, Student[],ArrayList etc.

World without Rules (Cont.)
 Parameter Type?
 Parameter can be in any order:
 ServletRequest/HttpServletRequest
 ServletResponse/HttpServletResponse
 HttpSession
 InputStream/java.io.Reader
 OutputStream/java.io.Writer
 @RequestParam("product") int id or any type
 @PathVariable String name or any type
 @CookieValue("cookie_name") String or any type
 @RequestHeader("content") String or any type
 @ModelAttribute User us or any custom object
 Errors
 BindingResult
 SessionStatus

@RequestParam
 Type Conversion
@RequestMapping("/login")
public void login(@RequestParam String userName,
@RequestParam int age){
}
 Optional Request parameter -- must use
object for optional
public void login(@RequestParam(required=false) String
userName){
}

@SessionAttribute
@Controller
@SessionAttributes("user")
public class LoginController {
public User login(@RequestParam int id){
return loginService.login(id);
}
}
User Object will be stored in session with key “user”

@PathVariable – REST URLs
 GET /students/find/5
@RequestMapping(“/find/{id}")
public ModelAndView findStudent(@PathVariable int id ,
Model model){
model.addAttribute("stu", studentService.getStudent(id));
return new ModelAndView("searchStudent");
}

Demo – @PathVariable – REST URLs

Demo – Ajax
 @ResponseBody annotation instructs
Spring MVC to serialize the Student to the
client.
 Spring MVC automatically serializes to
JSON because the client accepts that
content type
@RequestMapping(value="/student")
public @ResponseBody Student getStudent(
@RequestParam int id) {
return studentService.getStudent(id);
}

 Source Code
http://www.4shared.com/zip/sHRtnXXd/De
moSpringMVC.html
 You can find this presentation on
slideshare
http://www.slideshare.net/zeeshanhanif

Contact
zeeshanhanif@gmail.com
http://www.linkedin.com/in/zeeshanhanif
http://www.facebook.com/zeeshanhanif

Spring Web MVC

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