Struts Module Version 1

8/3/2019 Struts Module Version 1

1/82

Jakarta Struts

K.Srivatsan


2/82

Introduction to Struts

Its is an open source Web application framework developed as ApacheJakarta project

http://jakarta.apache.org/struts/

Created by Craig R. McClanahan and then donated to the Jakarta project

In June of 2001, Struts 1.0 was released.

Support for Struts comes in three forms. First is the API documentation that comes with Struts.

Second, Struts has a very active mailing list where you can get support forvirtually any question.

Third, several third-party consulting companies specialize in Struts support anddevelopment.


3/82

Framework

A framework is a set of classes which handles the flow necessary toperform a complex task.

It requires plug-in classes specific to the application and can also allow

additional plug-in classes to extend functionality.

A framework follows the "don't call us, we'll call you" idiom.

The framework calls the code to accomplish what needs to be done.

An AP I is a collection of routines,objects,modules etc that the application code

can link to and call to accomplish a task.

The AP I is totally distinct from the implementation.

a number of implementation of the servlet API,


4/82

Characteristics of Framework

Build applications faster as a result of similar structures.

Easier to maintain, and more consistent to their users.

Lose some creative freedom

Any substantive change to the framework's design would reduce its benefitsconsiderably,

The framework's defines an architecture for the application.


5/82

What is Struts?

Model-View-Controller (MVC) framework

Used for constructing web applications using Servlets and JSPs

Application can run on any Servlet container including J2EE compliant Appservers

It is Pattern oriented

MVC, Front Controller

Includes JSP custom tag libraries


6/82

Why Struts?

Encourages good design practice and modeling

Open source

Integrates well with J2EE

Good taglib support

Works with existing web apps

Unified error handling programmatically and declaratively


7/82

MVC - Model 1 & 2

MODEL - I

MODEL - 2


8/82

Struts: MVC-based Architecture

Controller mediates application flow and delegates to appropriate handler called Action

Action Handlers

use model components

Model encapsulates business logic or state

Control forwarded back

through the Controller to the appropriate View

The forwarding can be determined

consulting a set of mappings in configuration file

A loose coupling between the View and Model


9/82

Struts MVC Pattern


10/82

The Controller

Is the switch board of MVC architecture , requests goes through thecontroller

Responsible for flow control (action mapping) of the request handling reads

configuration file to determine the flow control

Struts framework provides a built-in base servlet

org.apache.struts.action.ActionServlet

Servlet mapping has to be configured in web.xml

Struts related configuration is done through struts-config.xml

Action Mapping defines the mapping between request URI of incoming

requests to specific Action class


11/82

ActionServlet

Performs the role of Controller Process user requests

Determine what the user is trying to achieve according to the request

Pull data from the model (if necessary) to be given to the appropriate view,

and Select the proper view to respond to the user

Delegates work to Action classes

Is responsible for initialization and clean-up of resources

Loads the application configuration corresponding to the init-param's in

web.xml


12/82

Configuration file

Configuration file contains action mappings URL to Action mappings

Controller uses these mappings to turn HTTP requests into application

actions

Determines forwarding/navigation

Mapping must specify

A request path

Action to act upon the request


13/82

Struts-Config File

Struts controller ActionServlet needs to know several things about how each request

URI should be mapped to an appropriate Action class

These requirements are encapsulated in a Java interface named ActionMappings

Struts framework creates Action Mapping object from

It also Contains definition of Form Beans used

contains FormBean definitions

contains action definitions

element for each action defined


14/82

struts-config.xml- Form bean

Its a Java class extending the ActionForm class) for the input form

Defined in struts-config.xml file

Contains only property getter and property setter methods for each field-no business

logic

Provides standard validation mechanism, has Two Attributes

name:

The name of the request (and session level attribute that this form bean will be stored as

type:

The fully-qualified Java class name of form bean


15/82

Each element requires the following attributes to be defined:

path: The application context-relative path to the action (URI of the request)

type: The fully qualified java classname of Action class

name: The name of element to use with this action

input: The name of the display page when input form validation error condition

occurs

scope: The scope in which form bean is created

validate: Whether to perform input form validation or not


16/82

struts-config.xml


17/82

ActionForm Bean & Controller

For each ActionForm bean defined in struts-config.xml file, ActionServlet

Check session scope for an instance of ActionForm bean

If it does not exist, controller creates one

Call corresponding setter method of ActionForm bean for every request

parameter whose name corresponds to the name of a property of the bean

Pass the updated ActionForm bean object as a parameter to execute()

method of Action class


18/82

Writing ActionForm Bean

Add just getter and setter methods for each property of a input form

Do not include any business logic code

Add a standard validation method called validate()

Controller will call this validation

Define a property (with associated getXxx and setXxx methods) for eachfield that is present in the input form


19/82

ActionClass

Focus on control flow

Process client request by calling other objects (BusinessLogic beans) inside its

execute() method

Returns an ActionForward object that identifies a destination resource to

which control should be forwarded to

The destination resource could be

JSP

Tile definition

Velocity template

Another Action


20/82

The ActionClass

Java class that extends org.jakarta.struts.action.Action that does the work

of the application Handle business logic by itself

Delegate business logic to Model components

Override execute(..) method of Action class -invoked by controller

public ActionForward execute(

ActionMapping mapping,

ActionForm form,

HttpServletRequest request,

HttpServletResponse response)

throws Exception;

Return an appropriate ActionForward object


21/82

View Components

JSP files which you write for your specific application Set of JSP custom tag libraries

Resource files for internationalization

Allows for fast creation of forms for an application

Works in concert with the controller Servlet

With just JSP, you have to do


22/82

View

ActionForward object tells Servlet controller which JSP page is to bedispatched to

JSP pages use ActionForm beans to get output Model data to display

Struts contains a series of tag libraries

Facilitates communication between HTML designers and developers

Facilitates dynamic Web content


23/82

web.xml

Has to have deployment descriptor that includes:

Configure ActionServlet instance and mapping

struts-config.xml file as

Define the Struts tag libraries

Server initializes this servlet when Server starts up.

The content of this element must be a positive integer indicating the

order in which the servlet should be loaded.

Lower integers are loaded before higher integers.


24/82

Example: web.xml

action org.apache.struts.action.ActionServlet config /WEB-INF/struts-config.xml


25/82

Struts Flow


26/82

Application Walk-through

Welcome To Validation

Welcome Struts Guide

My First Struts Example


27/82

Insurance.jsp

name

address

phone

pincode


28/82

The Formpublic class InsuranceForm extends ActionForm {

private String address;

private double phone;private String name;

private double pincode;

public String getAddress() {

return address;

public void setAddress(String a) {

this.address = a; }

public double getPhone() {

return phone;}

public void setPhone(double p) {

this.phone = p; }

public String getName() {

return name; }

public void setName(String n) {

this.name = n;

}

public double getPincode() {

return pincode;

}

public void setPincode(double p) {

this.pincode = p;

} }


29/82

Action Class

import com.training.InsuranceForm;

public class Action extends org.apache.struts.action.Action {

public ActionForward execute(


ActionForm form,

HttpServletRequest request,

HttpServletResponse response)

throws Exception {try {

ActionForward forward = new ActionForward();

InsuranceForm insuranceForm = (InsuranceForm) form;

ModelData md = new ModelData();

insuranceForm = md.getData(insuranceForm);

} catch (Exception e) { System.out.println(e);}

return(mapping.findForward("success"));

}

}


30/82

Model Data

package com.training;

public class ModelData {

public InsuranceForm getData(InsuranceForm frm)

{

frm.setAddress(frm.getAddress().toUpperCase());

frm.setPhone(frm.getPhone());

frm.setPincode(frm.getPincode());

frm.setName(frm.getName().toUpperCase());

returnfrm;

}

}


31/82

Success.jsp

Success.jsp

Thanks For Registering you have given the following information

Demo 1.2


32/82

Validation

Perform simple, prima facia validations

using the ActionForm validate() method , an optional one

Handle the "business logic" validation in the Action class


33/82

Validate Method

public ActionErrors validate(


HttpServletRequest request) {

ActionErrors errors = new ActionErrors();

if ((username == null) || (phone.length() == 0)) {

errors.add("err_order",

new org.apache.struts.action.ActionError

("error.field.required"));

}

return errors;

}


34/82

Application Errors in Action Class

Create ActionErrors object and return

ActionServlet can take action if a certain exception is thrown

Can be global or Action-based

Can either be a simple forward, or passed to a custom error handlerclass through default ExceptionHandler


35/82

Message Resources

The message resources section declares the location of properties file that

stores the key/value pairs of your application.

If a message is used in several places, it can be updated with a singlechange.

This is consistent with the Struts philosophy of making as many changes as

possible in config files, not in Java or JSP code.

if you use messages pervasively in your JSP pages, you caninternationalize your application by having multiple properties filescorresponding to the locale, as with standard I18N in Java

MessageResources.properties

MessageResources_jp.properties

MessageResources_es.properties

MessageResources_es_mx.properties


36/82

Advantages ofProperties Files

form.title=Registration

form.firstName=First name

:

The main attribute of the tag is the parameter attribute, which gives the location of theproperties file for your application relative to the \WEB-INF\classes\ directory of yourwebapp.

In the declaration, the .properties extension is implied.


37/82

Parameterized Messages

Properties File

error.missing=You must enter {0}, you are not authorised

error.number={0} and {1} are not whole numbers!

JSP Pages


38/82

Message Resources

Using the struts-config.xml file to configure your message resources is

preferred than in web.xml

Multiple message-resources tags could be used to load messages frommultiple files.

The key attribute to give a unique name to each bundle.


39/82

Tag Libraries Overview

Number of taglibs included as part of Struts

Usage is not required, but helpful

Bean tags

Tags for accessing Beans and their properties

Html tags

Form bridge between JSP view and other components

Logic tags Provides presentation logic tags that eliminate need for scriptlets

Template tags (Tiles in v1.1)

Tags to form JSP templates that include parameterized content

Nested Tags (v1.1)

Allows for object hierarchy Helpful for rendering lists of lists


40/82

Access toTag Libraries

All tag libraries are defined in web.xml using element

/WEB-INF/struts-bean.tld

/WEB-INF/struts-bean.tld

/WEB-INF/struts-html.tld

/WEB-INF/struts-html.tld


41/82

HTML Tags

Form bridge between JSP view and other components

Input forms are important for gathering data

Most of the actions of the HTML taglib involve HTML forms

Error messages, hyperlinking, internationalization


42/82

Start the page with this tag , it creates an html element .

The Attributes are

Locale : Set to true to store a locale in the session based on the currentrequests accept language header


43/82

The form Tag

Tag is used render a standard HTML form tag and to link the HTML form

with an ActionForm configured for the application.

Each field in the HTML form should correspond to a property of theActionForm.

When an HTML field name and a property name match, the property fromthe ActionForm is used to populate the HTML field.

When the HTML form is submitted, the framework will store the user's inputinto the ActionForm, again matching up the HTML field names to theproperty names.


44/82

To work with html forms , enclose the fields within this tag

The Attributes are

Action : the url to which this form is submitted

Focus : the field names to which initial focus will be assigned with a javascript function

Method : Default is post

Onsubmit : javascript event handler

Creates the submit button

The value for the action attribute is used to select the ActionMapping the page isassumed to be processing,

If extension mapping is being used (*.do), the action value should be equal to thevalue of the path attribute of the corresponding action element, optionally followed bythe correct extension suffix.


45/82

: Creates text field

This tag displays error messages as returned by your in the input page

Prroperty , the name of the property for which error message is stored

Error.header : Header text for error message

Error .footer : the footer for error message

Erros.prefix : text to be added before each message

Errors.suffix text that will be added after each error in the list


46/82

Creates a Text Area

To create check box

clickme Attribute

Value : the value to be transmitted if the check box is clicked when the form issubmitted,by default the value of on will be returned.

ToCreate radio button

red


47/82

Creates a Button with tag , can be connected to javascript funtions

using html button tag

function clicker()

{

confirm(you clicked the button);

}


48/82

This tag creates a HTML tag,the base url for this hyperlink is calcuated

based on the attribute.

Forward : use the value of this attribute as the name of the global actionforward

Action : use the value of this attribute as the name of an action

Href: use the value of this attribute

Page : generate a server relative uri including the context path andapplication prefix

register


49/82

and tags create controls and

elements , used to create scrollable list or drop down list boxes.

Mutiple1

: check box group


50/82

Handling property in Form Bean

String[] mulibox = new String[5];

public String[] getMultiBox()

{

return multibox ;

}

public setMultiBox(String[] multiBox)

{

this.multibox = multibox;

}


51/82

Example HTML Tag

Male Female

Age: " " 0-19 20-49


52/82

Logic Tags

The Logic tag library contains tags that are useful for managing conditional

generation of output text, looping over object collections for repetitivegeneration of output text, and application flow management.

The tags within the Logic tag library are into four separate categories

Value comparison

Substring matching Redirecting and forwarding

Collection utilities


53/82

Logic Tag Sample

It represents the body content of this tag for every element of a collection , whichmust be an Iterator a collection or an array

If we use custom tag that return an array of values Iterate tag can be used


54/82

Bean Tag Sample

Tags for accessing beans and their properties

Used to access data Creating Beans

Define a scripting variable (named by id) based on the value of abean property

Retrieving Value

Retrieves the value of the specified bean property and renders it to the pageoutput as a String.

Hello


55/82

DynaForm

ActionForms increases the number of classes to a project.

Properties need to be defined in the ActionForm to be able to capture datafrom the HTML form.

If a property is added or removed from the HTML form, the ActionFormclass may need to be modified and recompiled.

There is a dynamic form avoids having to create a concrete ActionFormclasse

The dynamic ActionForm is implemented by the base class

org.apache.struts.action.DynaActionForm, which extends theActionForm class.


56/82

Dyna Form

The properties that the Action Form defines The validate() method The reset() method

The properties for a DynaActionForm are configured in the Strutsconfiguration file,

The reset() method is that you have a little less control over whatyou do during the method.

The validation of the presentation data is a little more complicated,


57/82

Dyna Form-configuration file Form-property elements are defined for the dynamic form to have

properties.


58/82

Accesing DynaForm in Action class

DynaActionForm dynaActionForm = (DynaActionForm) form;

String uname = String)dynaActionForm.get("username");

String pwd =(String)dynaActionForm.get("password");


59/82

DispatchActionClass

This class provides a mechanism for modularizing a set of related

functions into a single action, and thus eliminates the need to createseparate, independent actions for each function.

Action extends org.apache.struts.actions.Dispatch Action;

Method call is determined based on the value of a requestparameter that is passed to it from the incoming request.

At run time, DispatchAction manages routing requests to theappropriate method in its subclass.


60/82

DispatchAction

Set up action mapping that specifies the name of a request parameter that

will be used to select which method should be called for each request.

execute method is omitted entirely, the custom methods have samesignature as execute

Value should be the name of the method that applies


61/82

DispatchAction

This class does not provide an implementation for the execute( ) method

Struts configuration file for an an action mapping


62/82

LookupDispatch Action

The org.apache.struts.actins.LookupDispatchAction , similar to Dispatch

Action except that it uses java map

The method name is selected based on the method specified in theproperties file

This class can also have multiple methods, where one of the methods is

invoked based on the value of a special request parameter that is specifiedthe configuration file.

It uses the value of the request parameter to perform a reverse lookup fromthe resource bundle using the parameter value, and match it to a method inthe class.

The getKeyMethodMap() method. returns a java.util.Map, which contains aset of key/value pairs.The keys of this Map should match those from theresource bundle.

For ardAction


63/82

ForwardAction

JSP should not be called directly and should be avoided.

If there is a need, without having a need to go through an Action class.

Use ForwardAction simply performs a forward to a URI that is configured forit.

In the Struts configuration file, you specify an element using theForwardAction as the type attribute:


64/82

Steps in Using ForwardAction


65/82

The ActionForward Class

Forwards are defined declaratively in the Struts configuration file.

There are two types of forwards that can be defined,

action-specific forward.

These forwards are available only to their respective action.

Action-specific forwards are defined by nesting the forward taginside an action tag,

globalforward

Global forwards are available throughout an application,


66/82

Forwards

LOCAL Forward

...

...

Local Forward


67/82

Local Forward

...

...

...

...

...


68/82

DAO Factory

The DAO Factory Class :

Its used to retrieve the object that implements the DAO Interface The DAO Interface

The DAO AP I is defined with the methods

The Concrete Class that implements the DAO interface

Contains logic for accessing data from a specific data source.

Data Transfer Objects Value Objects Used to transfer objects to transport data to and from the clients.

A Business Logic Bean

Contains the business logic of the application and will call DAO

implementing concrete class for database related operations.

In struts we use the Action class is used to call the DAO.


69/82

Data Access Object

The database access code is removed from the action class.

It has to be encapsulated behind the business API classes, using the DataAccess Object (DAO) pattern.

To Access Using DAO Pattern

1. Create a data access object factory.

2. Create an interface that defines the methods that you need.3. Create a data access object that implements the interface and that contains

the data access code.

4. Refer to the data access object from the Struts action class.


70/82

DAO Factory


import java.sql.Connection;

public class DAOFactory {

public DAOFactory() {

}

public static UserDAO createUserDAO(Connection connection){

return new OracleUserDAO(connection); }

}


71/82

The Interface with Required Method


import java.util.ArrayList;

public interface UserDAO {

public ArrayList getCustomers(int pid);

}

Th D t A Obj t


72/82

The DataAccess Object public class OracleUserDAO implements UserDAO {

private Connection connection;

private DataSource dataSource; public OracleUserDAO(Connection connection) {

this.connection = connection; }

public ArrayList getCustomers(int pid){

ArrayList customerList = new ArrayList();

try{

String sqlQuery = "SELECT * FROM sribooks where pub_id=?"; PreparedStatement prpStmt = connection.prepareStatement(sqlQuery);

prpStmt.setInt(1,pid);

ResultSet rs = prpStmt.executeQuery();

while (rs.next()) {

customerList.add(newBook(rs.getString(1),rs.getInt(2),rs.getFloat(3)));

} rs.close();

} catch (Exception e ) {

e.printStackTrace();

}


73/82

Action Class

public class DataSourceConnectionAction extends Action {

private DataSource dataSource; public ArrayList customerList = new ArrayList();

public ActionForward execute(ActionMapping mapping, ActionForm form,

HttpServletRequest request, HttpServletResponse response)

throws Exception {

HttpSession session = request.getSession(true)

InitialContext ctx = new InitialContext();

dataSource = (DataSource)ctx.lookup("myoracle");

Connection conn = dataSource.getConnection();

UserDAO dao = DAOFactory.createUserDAO(conn);

customerList = dao.getCustomers(lac.getPubid());

session.setAttribute("clist", customerList); }

return (mapping.findForward("success")); }


74/82

Validation Framework


75/82

Why Struts Validation Framework?

Issues with writing validate() method in ActionForm classes

You have to write validate() method for each ActionForm class, whichresults in redundant code

Changing validation logic requires recompiling

Struts validation framework addresses these issues

Validation logic is configured using built-in validation rules as opposedto writing it in Java code


76/82

Struts Validation Framework

Originated from generic Validator framework from Jakarta

Struts 1.1 includes this by default

Allows declarative validation for many fields

Formats

Dates, Numbers, Email, Credit Card, Postal Codes

Lengths

Minimum, maximum

Ranges

The built-in validation rules come with Javascript that allows you to doclient side validation

Custom Validation rules can be created and added to the definition file.

Can also define regular expressions

Things to do in order to use Validator


77/82

Things to do inorder to use Validator

framework

Configure Validator plugin

Configure validation.xml file (and validation-rules.xml file)

Extend ValidatorForm or DynaValidatorForm

Set validate=true on Action Mappings

Include the tag for client side validation in the form's JSP

page

How to Configure Validator Plugin


78/82

How to Configure Validator Plugin

Validator plugin should be configured in struts-config.xml

Just add the following element without any change


79/82

TwoValidatorConfiguration Files

validation-rules.xml Contains global set of validation rules

Provided by Struts framework

validation.xml

Application specific

Provided by application developer

It specifies which validation rules from validation-rules.xml file are usedby a particular ActionForm

No need to write validate() code in ActionForm

B ilt i i d lid ti l


80/82

Built-in required validation rule

function validateRequired(form) {

var isValid = true;

...

Att ib t f < lid t > El t


81/82

Attributes of Element

name: logical name of the validation rule

classname, method: class and method that contains the validation logic

methodParams: comma-delimited list of parameters for the method

msg: key from the resource bundle

Validator framework uses this to look up a message from Struts resourcebundle

depends: other validation rules that should be called first


82/82

validation.xml

Demo3.1

Struts Module Version 1

Documents

Transcript of Struts Module Version 1