Skillwise Struts.x

Agenda
 Struts Introduction
 Struts Web Flow
 Struts Architecture
 Struts Basic Example
 Dynamic Method Invocation
 Multiple Struts.xml files
 IOC and DI
 Interceptors
 Validation
 Internationalization
 Control Tags
 Struts2 with Jquery
 Build in Interceptor
 Custom Interceptor
 I18N

Struts2 is a free Open Source Framework
Apache Struts2 was originally known as WebWork 2. After working independently
for several years, the WebWork and Struts communities joined forces to create
Struts2.
It is based on MVC2 Architecture
In Struts 2 FilterDispatcher does the job of Controller.
Model contains the data and the business logic.
In Struts 2 the model is implemented by the Action component.
View is the presentation component of the MVC Pattern.
In Struts 2 View is implemented by JSP
Struts 2 is a pull-MVC framework. i.e. the data that is to be displayed to user has to
be pulled from the Action.
The “pull” comes from the views ability to pull data from an action using Value
Stack/OGNL.
Struts 2 Action class are plain POJO objects thus simplifying the testing of the code.
Struts Introduction

Servlet
(Controller)
1. Get Request parameters
Business Service
(Model)
2. Call Business Service
DB
Business Service talk to DB
JSP
(View)
3. Pass the result to the JSP
4. Return Formatted HTML
MVC

Why MVC
1. Business Logic (Model) is separate from controller.
2. View is separate from Controller
3. View is separate from Model
Conclusion : MVC Follows Separation of Concern Principal.

MVC Framework
1. It provide pre-build classes
2. It is a collections of Base classes and Jars
3. They are Extensible
4. Popular Java MVC are
Struts 1.x , Struts 2.x , JSF , Wicket , Spring MVC, Play, Grails

Framework vs Pattern
1. Pattern is the way you can architect your application.
2. Framework provides foundation (base) classes and
libraries.
3. Leverage industry best practices.

Struts 2 Web Flow
Struts MVC Flow

Five Core Components:
1. Actions
 The most basic unit of work that can be associated with a HTTP request coming from a user.
2. Interceptors
 They provide a way to supply pre-processing and post-processing around the action. They have access
to the action being executed, as well as all environmental variables and execution properties.
 Interceptors are conceptually the same as servlet filters, can be layered and ordered.
3. Value stack / OGNL.
 The value stack is exactly what it says it is – a stack of objects. OGNL stands for Object Graph
Navigational Language, and provides the unified way to access objects within the value stack.
4. Result types
 Chain, Dispatcher, Freemarker, HttpHeader, Redirect, Redirect-Action, Stream, Velocity, XSLT.
 If the attribute is not supplied, the default type “dispatcher” is used – this will render a JSP result.
5. View technologies.
 JSP
 Velocity Templates
 Free marker Templates
 XSLT Transformations
Struts 2 Core Components

Architecture of Struts 2
Struts 2 Architecture is based on WebWork 2 framework. It leverages the standard JEE
technologies such as Java Filters, JavaBeans, ResourceBundles, Locales, XML etc in its
architecture.
It is optional Filter
, and it is used to
integrate the Struts
with SiteMesh Plugin
Struts Architecture

architecture.
SiteMesh is a web-page
layout and decoration
framework and web
application integration
framework to aid in
creating large sites
consisting of many
pages for which a
consistent look/feel,
navigation and layout
scheme is required.
Struts Architecture

architecture.
The FilterDispatcher filter is
called which consults the
ActionMapper to determine
whether an Action should
be invoked
Struts Architecture

architecture.
If ActionMapper finds an Action
to be invoked, the FilterDispatcher
delegates control to ActionProxy.
Struts Architecture

architecture.
ActionProxy reads the configuration
file such as struts.xml.
ActionProxy creates an instance
of ActionInvocation class and
delegates the control.
Struts Architecture

architecture.
ActionInvocation is responsible
to invokes the Interceptors one by
one (if required) and then invoke
the Action.
Struts Architecture

architecture.
Once the Action returns, the
ActionInvocation is
responsible for looking up
the proper result associated
with the Action result code
mapped in struts.xml.
Struts Architecture

architecture.
The Interceptors are executed
again in reverse order and the
response is returned to the Filter
(In most cases to FilterDispatcher).
And the result is then sent to the
servlet container which in turns
send it back to client
Struts Architecture

Develop Struts First Application

Struts Basic Example
Struts First Program
For Creating Struts First Program, You required the Following things
a) JDK 1.5 or Higher
b) Servlet API and JSP API
c) J2EE Compliance Web Server or Application Server
d) Download the Following Jar Files from https://struts.apache.org/download.cgi

Step -1 Struts Filter Entry in web.xml
Web.xml
<filter>
<filter-name>struts2</filter-name>
<filter-
class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-
class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

Step -2 Create an Action Class
Creating Action

Step -3 Create a View
<%@ taglib prefix="s" uri="/struts-tags" %>

Step -4 Create struts.xml File
Struts.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
"http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
<package name="default" namespace="/" extends="struts-default">
<action name="welcome" class="com.srivastava.basics.HelloAction">
<result name="success">/index.jsp</result>
</action>
<action name="loginCheck" class="com.srivastava.basics.HelloAction"
method="checkLogin" >
<result name="login">/welcome.jsp</result>
<result name="error"></result>
</action>
</package>
</struts>

Login Page Demo
Login.jsp
LoginAction
Success
error

Struts 1.x v/s Struts 2.x
Feature Struts 1.x Struts 2.x
Action Classes Struts 1 requires Action classes to
extend an abstract base class. A
common problem in Struts 1 is
programming to abstract classes
instead of interfaces.
An Struts 2 Action may implement an Action interface,
along with other interfaces to enable optional and
custom services. Struts 2 provides a base
ActionSupport class to implement commonly used
interfaces. Albeit, the Action interface is not required.
Any POJO object with a execute signature can be used
as an Struts 2 Action object.
Binding
Values into
views
To access different objects , struts 1
uses the standard jsp implict objects
It use valuestack to hold the values and to reterive
the value from value stack it use OGNL (Object Graph
Navigational Language)
Servlet
Dependency
In action execute method , it has
HttpServletRequest and
HttpServletResponse Object, both
comes from servlet API
Not needed in struts 2 execute method
Testablity A major hurdle to testing Struts 1
Actions is that the execute method
exposes the Servlet API. A third-
party extension, Struts TestCase,
offers a set of mock object for Struts
1.
Struts 2 Actions can be tested by instantiating the
Action, setting properties, and invoking methods.
Dependency Injection support also makes testing
simpler.
No Action
Form
Struts 1 uses an ActionForm object
to capture input. Like Actions, all
ActionForms must extend a base
class. Since other JavaBeans cannot
be used as ActionForms, developers
often create redundant classes to
capture input.
Struts 2 uses Action properties as input properties,
eliminating the need for a second input objec
Control Of
Action
Execution
Struts 1 supports separate Request
Processors (lifecycles) for each
module, but all the Actions in the
module must share the same
lifecycle.
Struts 2 supports creating different lifecycles on a per
Action basis via Interceptor Stacks.

Multiple Struts.xml File
We can include other struts.xml-format files from a bootstrap struts.xml file
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<include file=“advice.xml"/>
<include file=“contract.xml"/>
<include file=“dms.xml"/>
</struts>

Designing UI in Struts 2
The form Tag
Eg.
<s:form action=“actionname” method =“post”>
</s:form>
The textfield tag
<s:textfield name=“userid” label =“userid” />
The TextArea tag
<s:textarea name=“address” label=“Address” cols=“15” rows=“2” />
UI

The password tag
<s:password name=“password” label=“Password” />
The Checkbox Tag
<s:checkbox name=“cricket” label=“Cricket” fieldValue=“C”/>
<s:checkbox name=“hockey” label=“Hockey” fieldValue=“H”/>
The Radio Tag
<s:radio name=“m_status” label=“Marital Status” list=“{‘Single’,’Married’}” />
The Hidden Tag
<s:hidden name=“empid” value=“Some Value” />
UI

The Combo box
<s:combobox label=“Country" headerKey="-1" headerValue="--- Select ---" list=“country"
name=“country" />
class Action extends ActionSupport
{
private List<String> country;
public void setCountry(List<String> country) { }
public List<String> getCountryList() { }
}
The submit tag
<s:submit/>
The datetimepicker tag
<s:datetimepicker name=“dob” label =“Date of Birth” displayFormat="dd MMMM, yyyy"
/>
UI

Using Freemarker template for Creating Custom UI

FreeMarker is a "template engine"; a generic tool to generate text output
To Print the Values in FTL
Welcome ${user}
If condition in FTL
<#if field.formatType??>
</#if>
Loops in FTL
<#list tabList as page>
</#list>
Freemarker

Creating Own Components Using FTL
Eg. Creating Password Field Using FTL
<input type="password" <#rt/>
name="${parameters.name?default("")?html}"<#rt/>
<#if parameters.get("size")??>
size="${parameters.get("size")?html}"<#rt/>
</#if>
<#if parameters.maxlength??>
maxlength="${parameters.maxlength?html}"<#rt/>
</#if>
<#if parameters.id??>
id="${parameters.id?html}"<#rt/>
</#if>
<#if parameters.get("size")??>
size="${parameters.get("size")?html}"<#rt/>
</#if>
<#if parameters.onblur??>
onblur="${parameters.onblur?html}"<#rt/>
</#if>
/>
NOTE: Store your FTL File in public-html template finnonepro
Freemarker

Calling FTL using <s:component tag> , place in JSP File
<s:component template="password.ftl" theme="finnonepro" id="28000005"
name="FW_SC_PW_OodPW">
<s:param name="maxlength" value="'20'"/>
<s:param name="size" value="'12'"/>
<s:param name="mandatory" value="'Y'"/>
</s:component>
Freemarker

IOC (Inversion of Control) and DI (Dependency Injection)
IOC and DI are programming design patterns, which are used to reduce coupling in
programming.
It follow the Following Principle:
a) You do not need to create your objects. You need to only describe how they should
be created. (This think is done by ObjectFactory)
To enable the IOC in Struts
a) Using an Enabler Interface
Eg. SessionAware, ApplicationAware etc.
IOC (Inversion of Control)

Exercise:
Create an Online Shopping Application, where user can login and register if the User is
New. Once User login in the System , the Application display the items to the User , so
User can choose it and buy the desire item. The Selected Item has the given features like
Item Name , Size , Color , Quantity and Price.
Once the User buy the selected item , the final bill is generated and display to the User

Interceptor
Interceptor is used for seperation of core functionality code in the form of
Interceptors makes Action more lightweight.
The purpose of Interceptors is to allow greater control over controller layer and
separate some common logic that applies to multiple actions.
All framework interceptors defined in struts-default.xml
Interceptors

Alias Interceptor
Alias Interceptor
This interceptor alias a named parameter to a different parameter name.
Suppose your jsp having two textfield name t1 and t2 and in your action class you defined t3
and t4 variable , so alias interceptor can map t1 with t3 alias and t2 with t4 alias.

Step-3 Entry in Struts.xml File

Step-4 ApplicationResource File

ExecuteAndWait Interceptor
While running a long action, the user may get impatient in case of a long delay in
response. To avoid this, the execAndWait Interceptor is used, which runs a long running
action in the background and display a page with a Loading to the user.

Step -4 Create struts.xml
an initial delay
in millis to wait
before the wait page is shown
Used for waking up at
certain intervals to check
if the background process is
already done. Default is
100 millis

Exception Interceptor
The Struts 2 framework provides the functionality of exception handling through the
Interceptor. Instead of displaying stack trace for the exception to the user, it is always
good to show a nicely designed page describing the real problem to the user.

Creating Own Interceptor
This framework provides the flexibility to create own interceptor classes to enable
additional logic which can be separated and refused in the Interceptor stack of different
action classes.
The Custom interceptor class need to be defined in the struts.xml file.

Step -1 Create Interceptor Java File

Step -2 Entry in struts.xml file

Validation Framework
Struts 2 based on a validation framework, which is provided by Xwork.
The Validation framework uses external metadata in the form of XML files to describe
what validation should be performed on your action.
Struts2 Validation Framework allows us to separate the validation logic from actual
Java/JSP code, where it can be reviewed and easily modified later.
Validation can be perform
a) Programmatic
b) XML Meta Data
Validation Framework

Validation Using XML Meta-Data

Step -3 create validation.xml file

Step -4 struts.xml
Note: validation.xml file placed in the same location , where Action is placed and it
is same name as action name and end with validation.xml file

Programmatic Validation
It is written in the Actionclass by overriding the
validate method , this method calls automatically
when user submit the page, it is call before the
execute method , and if any error occurred , it return
the “input” as a result , otherwise it execute the
execute method of the action

Step -1 Create an Action
Override the validate method
it comes from Validateable
interface, which is
implemented by
ActionSupport class

Internationalization
Internationalization is a technique for application development that support multiple
languages and data formats without having to rewrite programming logic.
Create different languages
application resource property file’s
and these files name end
with country language code
Note: Also Specify the application resource name and path in
struts.properties file, the path is required if you are not placed in
application resoource file in the src folder

Changing Browser Language
1 2
3

Control Tags
<s:if>
<s:iterator>

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