Developing Web Applications with Spring MVC Ryan Breidenbach Countrywide Financial Corporation

Token “Who Am I?” slide Developing JEE applications for the past 7 years Developing Spring applications for over 3 years Coauthor of Spring in Action Currently developing applications for Countrywide Financial Corporation

Developing JEE applications for the past 7 years

Developing Spring applications for over 3 years

Coauthor of Spring in Action

Currently developing applications for Countrywide Financial Corporation

Agenda Introduction to Spring MVC Overview of architecture Overview and examples of individual MVC components In depth examples of forms processing and validation Miscellaneous topics Questions

Introduction to Spring MVC

Overview of architecture

Overview and examples of individual MVC components

In depth examples of forms processing and validation

Miscellaneous topics

Questions

What is Spring MVC? Request-response based web application framework, such as Struts and WebWork Flexible and extensible via component’s interfaces Simplifies testing through Dependency Injection Simplifies form handling through its parameter binding, validation and error handling Abstracts view technology (JSP, Velocity, FreeMarker Excel , PDF)

Request-response based web application framework, such as Struts and WebWork

Flexible and extensible via component’s interfaces

Simplifies testing through Dependency Injection

Simplifies form handling through its parameter binding, validation and error handling

Abstracts view technology (JSP, Velocity, FreeMarker Excel , PDF)

Spring MVC Architecture

DispatcherServlet

DispatcherServlet Example of Front Controller pattern - entry point for all Spring MVC requests Loads WebApplicationContext and well are parent contexts Controls workflow and mediates between MVC components Loads sensible default components if none are configured

Example of Front Controller pattern - entry point for all Spring MVC requests

Loads WebApplicationContext and well are parent contexts

Controls workflow and mediates between MVC components

Loads sensible default components if none are configured

Configuring the DispatcherServlet web.xml … <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>*.htm</url-pattern> </servlet-mapping> …

web.xml

…

<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>*.htm</url-pattern>

</servlet-mapping>

…

Configuring the DispatcherServlet (cont’d) web.xml … <servlet> <servlet-name>dispatcher</servlet-name> <servlet-class> org.springframework.web.servlet.DispatcherServlet </servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>WEB-INF/mvc.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> …

web.xml

…

<servlet>

<servlet-name>dispatcher</servlet-name>

<servlet-class>

org.springframework.web.servlet.DispatcherServlet

</servlet-class>

<init-param>

<param-name>contextConfigLocation</param-name>

<param-value>WEB-INF/mvc.xml</param-value>

</init-param>

<load-on-startup>1</load-on-startup>

</servlet>

…

Configuring the DispatcherServlet (cont’d) web.xml … <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/services.xml</param-value> </context-param> <listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener> … configures parent context

web.xml

…

<context-param>

<param-name>contextConfigLocation</param-name>

<param-value>/WEB-INF/services.xml</param-value>

</context-param>

<listener>

<listener-class>

org.springframework.web.context.ContextLoaderListener

</listener-class>

</listener>

…

HandlerMapping

HandlerMapping Maps incoming requests to a corresponding Handler, typically a Controller Rarely needs to be implemented directly – many useful implementations are provided Also ties Interceptors to a mapped Controllers Can provided multiple HandlerMappings; priority is set using Ordered interface

Maps incoming requests to a corresponding Handler, typically a Controller

Rarely needs to be implemented directly – many useful implementations are provided

Also ties Interceptors to a mapped Controllers

Can provided multiple HandlerMappings; priority is set using Ordered interface

BeanNameUrlHandlerMapping Maps a URL to a bean registered with the same name – e.g. /simple.htm maps to a bean named “/simple.htm” Can give bean multiple names (aliases) separated by spaces Must use name attribute – “/” is not allowed in XML id attribute Can use wild card in bean names (/simple*) Default HandlerMapping , but not preferred

Maps a URL to a bean registered with the same name – e.g. /simple.htm maps to a bean named “/simple.htm”

Can give bean multiple names (aliases) separated by spaces

Must use name attribute – “/” is not allowed in XML id attribute

Can use wild card in bean names (/simple*)

Default HandlerMapping , but not preferred

BeanNameUrlHandlerMapping dispatcher-servlet.xml <bean class=&quot;org.springframework.web.servlet. handler.BeanNameUrlHandlerMapping&quot;/> <bean name=&quot;/simple.htm /simpleSimon.htm&quot; class=&quot;com.twoqubed.mvc.web.SimpleController&quot;> … </bean>

dispatcher-servlet.xml

<bean class=&quot;org.springframework.web.servlet.

handler.BeanNameUrlHandlerMapping&quot;/>

<bean name=&quot;/simple.htm /simpleSimon.htm&quot;

class=&quot;com.twoqubed.mvc.web.SimpleController&quot;>

…

</bean>

SimpleUrlHandlerMapping Most common way to map request URLs to handlers Configured by a list of name/value pairs consisting of URLs and bean names Can use wild card in bean names (/simple*)

Most common way to map request URLs to handlers

Configured by a list of name/value pairs consisting of URLs and bean names

Can use wild card in bean names (/simple*)

SimpleUrlHandlerMapping dispatcher-servlet.xml … <bean class=&quot;org.springframework.web.servlet. handler.SimpleUrlHandlerMapping&quot;> <property name=&quot;mappings&quot;> <value> /simple.htm=simpleController /test*=testController </value> </property> </bean> …

dispatcher-servlet.xml

…

<bean class=&quot;org.springframework.web.servlet.

handler.SimpleUrlHandlerMapping&quot;>

<property name=&quot;mappings&quot;>

<value>

/simple.htm=simpleController

/test*=testController

</value>

</property>

</bean>

…

ControllerClassNameHandlerMapping Part of Spring 2.0's Convention over Configuration Maps a URL to the shortened class name of a Controller bean Removed &quot;Controller&quot; from class name Converts to all lower case Prepend and &quot;/&quot; and append a &quot;*&quot; Example: SimpleController -> /simple* Greatly reduces amount of mapping configurations

Part of Spring 2.0's Convention over Configuration

Maps a URL to the shortened class name of a Controller bean

Removed &quot;Controller&quot; from class name

Converts to all lower case

Prepend and &quot;/&quot; and append a &quot;*&quot;

Example:

SimpleController -> /simple*

Greatly reduces amount of mapping configurations

ControllerClassNameHandlerMapping dispatcher-servlet.xml … <bean class=&quot;org.springframework.web.servlet.mvc. support.ControllerClassNameHandlerMapping&quot; /> …

dispatcher-servlet.xml

…

<bean class=&quot;org.springframework.web.servlet.mvc.

support.ControllerClassNameHandlerMapping&quot; />

…

Controllers

Controller interface Handles the processing of the request Interface parameters mimics HttpServlet handleRequest(HttpServletRequest, HttpServletResponse) Returns a ModelAndView object Implementations are typically thread-safe Rarely implemented directly – Spring provides many useful implementations

Handles the processing of the request

Interface parameters mimics HttpServlet

handleRequest(HttpServletRequest, HttpServletResponse)

Returns a ModelAndView object

Implementations are typically thread-safe

Rarely implemented directly – Spring provides many useful implementations

ModelAndView object Encapsulates both model and view that is to be used to render model Model is represented as a java.util.Map Objects can be added to without name: addObject(String, Object) – added with explicit name addObject(Object) – added using name generation ( Convention over Configuration ) View is represented by String or View object Analogous to Struts Action

Encapsulates both model and view that is to be used to render model

Model is represented as a java.util.Map

Objects can be added to without name:

addObject(String, Object) – added with explicit name

addObject(Object) – added using name generation ( Convention over Configuration )

View is represented by String or View object

Analogous to Struts Action

Controller implementations Typical Controllers in your application will: Be completely configured via wiring (no code) Contain simple web processing Handle web layer and defer to service layer for additional processing Parameter handling View determination Input validation

Typical Controllers in your application will:

Be completely configured via wiring (no code)

Contain simple web processing

Handle web layer and defer to service layer for additional processing

Parameter handling

View determination

Input validation

AbstractController Provides minimal behavior Used for handling simple requests protected ModelAndView handleRequestInternal( HttpServletRequest request, HttpServletResponse response) { String text = service.getText(); return new ModelAndView( &quot;simple&quot;, &quot;text&quot;, text); }

Provides minimal behavior

Used for handling simple requests

protected ModelAndView handleRequestInternal(

HttpServletRequest request,

HttpServletResponse response) {

String text = service.getText();

return new ModelAndView(

&quot;simple&quot;, &quot;text&quot;, text);

}

AbstractController Provides minimal behavior Used for handling simple requests protected ModelAndView handleRequestInternal( HttpServletRequest request, HttpServletResponse response) { String text = service.getText(); return new ModelAndView( &quot;simple&quot;, &quot;text&quot;, text); }

Provides minimal behavior

Used for handling simple requests

protected ModelAndView handleRequestInternal(

HttpServletRequest request,

HttpServletResponse response) {

String text = service.getText();

return new ModelAndView(

&quot;simple&quot;, &quot;text&quot;, text);

}

ThrowawayController Not part of the Controller hierarchy Parameters are mapped directly onto the controller Useful when there is not model object to map to Must scope bean as prototype since these are inherently not thread-safe

Not part of the Controller hierarchy

Parameters are mapped directly onto the controller

Useful when there is not model object to map to

Must scope bean as prototype since these are inherently not thread-safe

ThrowawayController dispatcher-servlet.xml … <bean id=&quot;exampleThrowawayController&quot; class=&quot;com.twoqubed.mvc.web. ExampleThrowawayController&quot; scope=&quot;prototype&quot; /> … configured as prototype bean

dispatcher-servlet.xml

…

<bean id=&quot;exampleThrowawayController&quot;

class=&quot;com.twoqubed.mvc.web.

ExampleThrowawayController&quot;

scope=&quot;prototype&quot; />

…

ThrowawayController public class ExampleThrowawayController implements ThrowawayController { private String message; public void setMessage(String message) { this.message = message; } public ModelAndView execute() throws Exception { String hashCodeMessage = &quot;[&quot; + hashCode() + &quot;] - &quot; + message; return new ModelAndView(&quot;throwaway&quot;, &quot;message&quot;, hashCodeMessage); } }

public class ExampleThrowawayController

implements ThrowawayController {

private String message;

public void setMessage(String message) {

this.message = message;

}

public ModelAndView execute() throws Exception {

String hashCodeMessage = &quot;[&quot; + hashCode()

+ &quot;] - &quot; + message;

return new ModelAndView(&quot;throwaway&quot;, &quot;message&quot;,

hashCodeMessage);

}

}

Command Controllers Family of Controllers that bind request parameters to command objects Command object can be any POJO – typically a domain object Provides functionality: Binding custom types Automatic and custom validation Automatically or programmatically creating command object We will cover in more detail later…

Family of Controllers that bind request parameters to command objects

Command object can be any POJO – typically a domain object

Provides functionality:

Binding custom types

Automatic and custom validation

Automatically or programmatically creating command object

We will cover in more detail later…

Command Controllers AbstractCommandController – Provides binding and validation SimpleFormController – In addition to binding and validation, provides rich work flow for processing forms Most useful for processing form Detailed example to come later AbstractWizardFormController – For forms that span multiple pages

AbstractCommandController – Provides binding and validation

SimpleFormController – In addition to binding and validation, provides rich work flow for processing forms

Most useful for processing form

Detailed example to come later

AbstractWizardFormController – For forms that span multiple pages

Additional Controllers ServletWrappingController and ServletForwardingController – specialty Controllers to wrap Struts servlet in Spring interceptors ParameterizableViewController – simply forwards to a configured view without exposing view technology to client UrlFilenameViewController – converts a URL to a view name

ServletWrappingController and ServletForwardingController – specialty Controllers to wrap Struts servlet in Spring interceptors

ParameterizableViewController – simply forwards to a configured view without exposing view technology to client

UrlFilenameViewController – converts a URL to a view name

Interceptors

Interceptors Add additional functionality before and after request Contains to interception methods – preHandle and postHandle Contains one callback method – afterCompletetion Associated with a set of Controllers via a HandlerMapping

Add additional functionality before and after request

Contains to interception methods – preHandle and postHandle

Contains one callback method – afterCompletetion

Associated with a set of Controllers via a HandlerMapping

Interceptor implementations Implement either HandlerInterceptor or WebRequestInterceptor Spring provides a few implementations OvenXxxInViewInteceptor – Used with ORM frameworks JDO, JPA and Hibernate UserRoleAuthorizationInterceptor – Provides authorization against a set of roles Other useful customizations: custom security, caching, …

Implement either HandlerInterceptor or WebRequestInterceptor

Spring provides a few implementations

OvenXxxInViewInteceptor – Used with ORM frameworks JDO, JPA and Hibernate

UserRoleAuthorizationInterceptor – Provides authorization against a set of roles

Other useful customizations: custom security, caching, …

ViewResolver

ViewResolver Resolves a logical view name to a View object Orderable, so they be chained For JSP user, typical implementation is InternalResourceViewResolver: <bean id=&quot;internalResourceViewResolver&quot; … <property name=&quot;prefix&quot; value=&quot;/WEB-INF/jsp/&quot; /> <property name=&quot;suffix&quot; value=&quot;.jsp&quot; /> </bean>

Resolves a logical view name to a View object

Orderable, so they be chained

For JSP user, typical implementation is InternalResourceViewResolver:

<bean id=&quot;internalResourceViewResolver&quot; …

<property name=&quot;prefix&quot; value=&quot;/WEB-INF/jsp/&quot; />

<property name=&quot;suffix&quot; value=&quot;.jsp&quot; />

</bean>

Other ViewResolver Implementations VelocityViewResolver – Convenience class for Velocity templates FreeMarkerViewResolver – Convenience class for FreeMarker templates ResourceBundleViewResolver Mappings are contained within a properties file Supports internationalization XmlViewResolver - Mappings are contained with an XML file

VelocityViewResolver – Convenience class for Velocity templates

FreeMarkerViewResolver – Convenience class for FreeMarker templates

ResourceBundleViewResolver

Mappings are contained within a properties file

Supports internationalization

XmlViewResolver - Mappings are contained with an XML file

View

View Contains implementations for several template technologies: InternalResourceView (JSP) JstlView (JSP + JSTL) VelocityView (Velocity) FreeMarkerView (FreeMarker) TilesView (Tiles) TilesJstlView (Tiles + JSTL)

Contains implementations for several template technologies:

InternalResourceView (JSP)

JstlView (JSP + JSTL)

VelocityView (Velocity)

FreeMarkerView (FreeMarker)

TilesView (Tiles)

TilesJstlView (Tiles + JSTL)

View Also contains views that support rendering Excel files PDF files XSLT results Jasper Reports

Also contains views that support rendering

Excel files

PDF files

XSLT results

Jasper Reports

Processing forms with Spring MVC Leveraging workflow provided by SimpleFormController Provides both form display and processing work flow with custom hooks Be default, GET indicates form displaying and POST indicates form processing Displaying and processing done by same Controller Complete workflow is quite involved – we will only hit the highlights

Leveraging workflow provided by SimpleFormController

Provides both form display and processing work flow with custom hooks

Be default, GET indicates form displaying and POST indicates form processing

Displaying and processing done by same Controller

Complete workflow is quite involved – we will only hit the highlights

Registering the Command class SimpleFormControllers are associated with a Command class Since these are tightly coupled, configuring with the Controller class is acceptable public class PlayerFormController extends SimpleFormController { public PlayerFormController() { setCommandClass(Player.class); setCommandName(&quot;player&quot;); }

SimpleFormControllers are associated with a Command class

Since these are tightly coupled, configuring with the Controller class is acceptable

public class PlayerFormController

extends SimpleFormController {

public PlayerFormController() {

setCommandClass(Player.class);

setCommandName(&quot;player&quot;);

}

Displaying a form We will discuss three methods in the work flow for displaying the form formBackingObject – Returns the command object used in the form. initBinder – Registered custom PropertyEditors for rendering command properties referenceData – Loads additional data to be displayed on page

We will discuss three methods in the work flow for displaying the form

formBackingObject – Returns the command object used in the form.

initBinder – Registered custom PropertyEditors for rendering command properties

referenceData – Loads additional data to be displayed on page

Processing a form Two main methods for form processing are: onBindAndValidate() – Allows for custom binding and validation doSubmitAction() – Callback to handle successful form submission. Typical implementation would be to persist command object to database.

Two main methods for form processing are:

onBindAndValidate() – Allows for custom binding and validation

doSubmitAction() – Callback to handle successful form submission. Typical implementation would be to persist command object to database.

Spring MVC Grab Bad Other Spring MVC functionality not covered (but is cool nonetheless) Transparent handling of Multipart requests Support for customized Look & Feels through Themes Support for internalization Convenience ServletContextListener for initializing Log4J

Other Spring MVC functionality not covered (but is cool nonetheless)

Transparent handling of Multipart requests

Support for customized Look & Feels through Themes

Support for internalization

Convenience ServletContextListener for initializing Log4J

Questions Resources Presentation and code http://www.twoqubed.com/svn/presentations/tags Spring Framework forms http://forum.springframework.org Spring MVC Official Documentation http://static.springframework.org/spring/docs/2.0.x/reference/mvc.html Spring Tag Library Official Documentation http://static.springframework.org/spring/docs/2.0.x/reference/spring-form.tld.html

Resources

Presentation and code

http://www.twoqubed.com/svn/presentations/tags

Spring Framework forms

http://forum.springframework.org

Spring MVC Official Documentation

http://static.springframework.org/spring/docs/2.0.x/reference/mvc.html

Spring Tag Library Official Documentation

http://static.springframework.org/spring/docs/2.0.x/reference/spring-form.tld.html