Struts Intro Course

8/14/2019 Struts Intro Course

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Project Refinery, Inc. 1

STRUTSPart of the Jakarta Project

Sponsored by the

Apache Software Foundation

Developed by: Roger W Barnes of Project Refinery, Inc.

Introduction to Struts


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STRUTS Objectives

Course Overview

Unit 1 - Model-View-Controller Design

PatternUnit 2 - Model Components

Unit 3 - View Components

Unit 4 - Controller ComponentsUnit 5 - Tag Libraries


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STRUTS Objectives

Unit 6 - STRUTS Configuration File

Unit 7 - Web Application Descriptor File

Unit 8 - Application Resources FileUnit 9 Resources


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Model-View-Controller DesignPattern

Unit 1


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STRUTS MVC Design Pattern

Central controller mediates application flow

Controller delegates to appropriate handler

Handlers are tied to model componentsModel encapsulates business logic

Control forwarded back through the

Controller to the appropriate View


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Configuration file contains action

mappings (determines navigation)

Controller uses mappings to turn HTTPrequests into application actions

Mapping must specify

A request pathObject type to act upon the request


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Model Components

Unit 2



STRUTS Model Components

Model divided into concepts Internal state of the system

Actions that can change that state Internal state of system represented by JavaBeans

Enterprise JavaBeans




JavaBeans and Scope Page visible within a single JSP page, for the

lifetime of the current request

Request visible within a single JSP page, as wellas to any page or servlet that is included in thispage, or forwarded to by this page

Session visible to all JSP pages and servletsthat participate in a particular user session, across

one or more requests Application - visible to all JSP pages and servlets

that are part of a web application




ActionForm Beans Extends the ActionForm class Create one for each input form in the application If defined in the ActionMapping configuration file, the

Controller Servlet will perform the following: Check session for instance of bean of appropriate class If no session bean exists, one is created automatically For every request parameter whose name corresponds to the

name of a property in the bean, the corresponding setter

method will be called The updated ActionForm bean will be passed to the Action

Class perform() method when it is called, making these valuesimmediately available


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When coding ActionForm beans consider: The ActionForm class itself requires no specific

methods to be implemented. It is used to identify therole these particular beans play in the overall

architecture. Typically, an ActionForm bean will haveonly property getter and property setter methods,with no business logic

The ActionForm object also offers a standardvalidation mechanism. If you override a "stub"

method, and provide error messages in the standardapplication resource, Struts will automaticallyvalidate the input from the form


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Continued Define a property (with associated getXxx() and setXxx()

methods) for each field that is present in the form. The fieldname and property name must match according to the usualJavaBeans conventions

Place a bean instance on your form, and use nested propertyreferences. For example, you have a "customer" bean on yourAction Form, and then refer to the property "customer.name"in your JSP view. This would correspond to the methodscustomer.getName() and customer.setName(string

Name) on your customer bean


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System State Beans Actual state of a system is normally represented

as a set of one or more JavaBeans classes,

whose properties define the current state A shopping cart system, for example, will include a

bean that represents the cart being maintained for

each individual shopper, and will (among other

things) include the set of items that the shopperhas currently selected for purchase


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STRUTS Model Components Business Logic Beans

Should encapsulate the functional logic of your application asmethod calls on JavaBeans designed for this purpose

For maximum code re-use, business logic beans should bedesigned and implemented so that they do not know they arebeing executed in a web application environment

For small to medium sized applications, business logic beansmight be ordinary JavaBeans that interact with system statebeans passed as arguments, or ordinary JavaBeans that accessa database using JDBC calls


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Business Logic Beans - Continued

For larger applications, these beans will

often be stateful or stateless Enterprise

JavaBeans (EJBs)


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Accessing Relational DatabasesStruts can define the datasources for an

application from within its standard

configuration file

A simple JDBC connection pool is also

provided


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View Components

Unit 3


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STRUTS View Components

Internationalized Messages Struts builds upon Java platform to provide assistance for

building internationalized and localized applications Locale - fundamental Java class that supports internationalization

ResourceBundle - supports messages in multiple languages PropertyResourceBundle - standard implementation of

ResourceBundle that allows you to define resources using the same"name=value" syntax used to initialize properties files

MessageFormat - allows you to replace portions of a message stringwith arguments specified at run time

MessageResources - lets you treat a set of resource bundles like adatabase, and allows you to request a particular message string for aparticular Locale


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ApplicationResources.propertiesContains the messages in the default language

for your server. If your default language is

English, you might have an entry like this:prompt.hello=Hello

ApplicationResources_xx.propertiesContains the same messages in the language

whose ISO language code is "xx"


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Forms and FormBean interactionsHTML Forms and their limitations

Errors not easily handled


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Building Forms with Struts The taglib directive tells the JSP page compiler where

to find the tag library descriptorfor the Struts tag library

message tag is used to look up internationalized

message strings from a MessageResources objectcontaining all the resources for this application

The errors tag displays any error messages that have

been stored by a business logic component, or nothing if

no errors have been stored


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Useful Presentation Tags [logic] iterate repeats its tag body once for each element of

a specified collection (which can be an Enumeration, aHashtable, a Vector, or an array of objects)

[logic] present depending on which attribute is specified,this tag checks the current request, and evaluates thenested body content of this tag only if the specified value ispresent

[logic] notPresent the companion tag to present, notPresentprovides the same functionality when the specified attribute

is not present
http://../Java%20Docs/STRUTS/Docs/struts-logic.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-logic.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-logic.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-logic.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-logic.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-logic.html


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Useful Presentation Tags continued [html] link generates a HTML element as an anchor

definition or a hyperlink to the specified URL, and automaticallyapplies URL encoding to maintain session state in the absenceof cookie support

[html] img generates a HTML element with the ability todynamically modify the URLs specified by the "src" and"lowsrc" attributes in the same manner that can

[bean] parameterretrieves the value of the specified requestparameter, and defines the result as a page scope attribute of

type String or String
http://../Java%20Docs/STRUTS/Docs/struts-html.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-html.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-bean.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-bean.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-html.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-html.html


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Automatic Form Validation Struts offers an additional facility to validate the input

fields it has received

To utilize this feature, override the validate() method in

your ActionForm class

The validate() method is called by the controller servlet

after the bean properties have been populated, but

before the corresponding action class's perform()

method is invoked


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Page Composition with IncludesThe development of the various segments of a site

is easier if you can divide up the work, and assigndifferent developers to the different segments

Use the include capability of JavaServer Pagestechnology to combine the results into a singleresult page, or use the include tag provided withStruts


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Page Composition with Includes continued There are three types ofinclude available, depending on

when you want the combination of output to occur: An directive can include a file

that contains java code or jsp tags The include action () is processed at request time, and is handledtransparently by the server

The bean:include tag takes either a an argument "forward"representing a logical name mapped to the jsp to include, or the"id" argument, which represents a page context String variable toprint out to the jsp page
http://../Java%20Docs/STRUTS/Docs/struts-bean.htmlhttp://../Java%20Docs/STRUTS/Docs/struts-bean.html


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Controller Components

Unit 4


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STRUTS Controller Components

Struts includes a Servlet that

implements the primary function of

mapping a request URI to an Actionclass (ActionServlet)


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Your primary responsibilities are: Write an Action class (that is, an extension of the Action

class) for each logical request that may be received

Write the action mapping configuration file (in XML) that is

used to configure the controller servlet (struts-config.xml) Update the web application deployment descriptor file (in

XML) for your application to include the necessary Strutscomponents

Add the appropriate Struts components to your application


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Action Classes:The Action class defines a perform

method that you override public ActionForward

perform(ActionMapping mapping,ActionForm form, HttpServletRequestrequest, HttpServletResponse response)

throws IOException, ServletException;


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The goal of an Action class is toprocess this request, and then to return

an ActionForward object that identifiesthe JSP page (if any) to which control

should be forwarded to generate the

corresponding response


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A typical Action class will implement the following logicin its perform() method Validate the current state of the user's session

If validation has not yet occurred, validate the form beanproperties as necessary

Perform the processing required to deal with this request

Update the server-side objects that will be used to create thenext page of the user interface

Return an appropriate ActionForward object that identifies theJSP page to be used to generate this response, based on the

newly updated beans


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Design issues to remember when coding Actionclasses include the following The controller Servlet creates only one instance of

yourAction class, and uses it for all requests. Thus,

you need to code yourAction class so that it operatescorrectly in a multi-threaded environment, just as youmust code a Servlet's service() method safely

The most important principle that aids in thread-safecoding is to use only local variables, not instance

variables, in yourAction class


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Design issues to remember when coding Action classesinclude the following continued The beans that represent the Model of your system may throw

exceptions due to problems accessing databases or otherresources. You should trap all such exceptions in the logic of

yourperform() method, and log them to the application logfile As a general rule, allocating scarce resources and keeping them

across requests from the same user (in the user's session) cancause scalability problems


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The ActionMapping Implementation type - Fully qualified Java class name of the Action

implementation class used by this mapping. name - The name of the form bean defined in the config file

that this action will use path - The request URI path that is matched to select this

mapping. See below for examples of how matching works. unknown - Set to true if this action should be configured as

the default for this application, to handle all requests nothandled by another action. Only one action can be defined asa default within a single application.

validate - Set to true if the validate() method of the actionassociated with this mapping should be called.


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The Actions Mapping Configuration File The developer's responsibility is to create an XML

file named struts-config.xml, and place it in the

WEB-INF directory of your application The outermost XML element must be

Inside of the element, there two

important elements that you use to describe youractions:


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This section contains your form bean

definitions. You use a element for

each form bean, which has the following

important attributes: name: The name of the request or session level

attribute that this form bean will be stored as

type: The fully-qualified Java classname of your form

bean


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This section contains your action definitions. You

use an element for each of your actions

you would like to define. Each action element has

requires the following attributes to be defined: path: The application context-relative path to the action

type: The fully qualified java classname of your Action

class

name: The name of your element to usewith this action


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STRUTS Controller Components One more section of good use is the

section, which specifies data sources that your applicationcan use.This is how you would specify a basic data sourcefor your application inside of struts-config.xml:


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The Web Application Deployment

DescriptorThe final step in setting up the application

is to configure the application deployment

descriptor (stored in file WEB-INF/web.xml) to include all the Struts

components that are required


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Tag Libraries

Unit 5


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STRUTS Tag Libraries

HTML Tags

Bean Tags

Logic TagsTemplate Tags

Custom Tags


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HTML Tags

The tags in the Struts HTML library form a bridgebetween a JSP view and the other componentsof a Web application. Since a dynamic Webapplication often depends on gathering data froma user, input forms play an important role in the

Struts framework. Consequently, the majority ofthe HTML tags involve HTML forms. Otherimportant issues addressed by the Struts-HTMLtags are messages, error messages, hyperlinking

and internationalization.


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HTML Tags

HTML "form" tags button

cancel

checkboxes

file

hidden

image

multibox

password input fields radio buttons

reset buttons

HTML "form" tags select lists with

embedded

option

options submit buttons

text input fields

textareas

HTML Tags T i l HTML F


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HTML Tags Typical HTML Form

First Name

Street Address

City

State

Postal Code

HTML Tags T i l St t F


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HTML Tags Typical Struts Form

B T


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Bean Tags The "struts-bean" tag library provides substantial enhancements to

the basic capability provided by , as discussed inthe following sections: Bean Properties - Extended syntax to refer to JavaBean properties with

simple names (same as the standard JSP tags and), nested names (a property named address.cityreturns the value retrieved by the Java expression

getAddress().getCity()), and indexed names (a property namedaddress[3] retrieves the fourth address from the indexed "address"property of a bean).

Bean Creation - New JSP beans, in any scope, can be created from a

variety of objects and APIs associated with the current request, or with

the servlet container in which this page is running.

Bean Output - Supports the rendering of textual output from a bean (or

bean property), which will be included in the response being created by

your JSP page.

Bean Tags


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Bean TagsTag Name Description

cookie Define a scripting variable based on the value(s) of the specified request cookie.

define Define a scripting variable based on the value(s) of the specified bean property.

header Define a scripting variable based on the value(s) of the specified request header.

include Load the response from a dynamic application request and make it available as a bean.

message Render an internationalized message string to the response.

page Expose a specified item from the page context as a bean.

parameter Define a scripting variable based on the value(s) of the specified request parameter.

resource Load a web application resource and make it available as a bean.

size Define a bean containing the number of elements in a Collection or Map.

struts Expose a named Struts internal configuration object as a bean.

write Render the value of the specified bean property to the current JspWriter.

Bean Tag Example


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Bean Tag Example

Logic Tags


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Logic Tags

The Logic tag library contains tags that are

useful in managing conditional generation

of output text, looping over object

collections for repetitive generation of

output text, and application flowmanagement.

Logic Tags


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Logic Tags For tags that do value comparisons (equal,

greaterEqual, greaterThan, lessEqual, lessThan,notEqual), the following rules apply: The specified value is examined. If it can be converted

successfully to a double or a long, it is assumed that theultimate comparison will be numeric (either floating point or

integer). Otherwise, a String comparison will be performed. The variable to be compared to is retrieved, based on the

selector attribute(s) (cookie, header, name, parameter,property) present on this tag. It will be converted to theappropriate type for the comparison, as determined above.

A request time exception will be thrown if the specified variablecannot be retrieved, or has a null value.

The specific comparison for this tag will be performed, and the

nested body content of this tag will be evaluated if the

comparison returns a true result.

Logic Tags


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Logic Tags For tags that do substring matching (match,

notMatch), the following rules apply: The specified variable is retrieved, based on theselector attribute(s) (cookie, header, name,parameter, property) present on this tag. Thevariable is converted to a String, if necessary.

A request time exception will be thrown if the specified

variable cannot be retrieved, or has a null value.

The specified value is checked for existence as a

substring of the variable, in the position specified by

the location attribute, as follows: at the beginning (iflocation is set to start), at the end (if location is set toend), or anywhere (if location is not specified).

Logic Tags


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Logic TagsTag Name Description

emptyEvaluate the nested body content of this tag if the requested variable is eithernull or an empty string.

equalEvaluate the nested body content of this tag if the requested variable is equal

to the specified value.forward Forward control to the page specified by the specified ActionForward entry.

greaterEqualEvaluate the nested body content of this tag if requested variable is greaterthan or equal to specified value.

greaterThanEvaluate the nested body content of this tag if the requested variable is greaterthan the specified value.

iterate Repeat the nested body content of this tag over a specified collection.

lessEqualEvaluate the nested body content of this tag if requested variable is greater

than or equal to specified value.lessThan

Evaluate the nested body content of this tag if the requested variable is lessthan the specified value.

matchEvaluate the nested body content of this tag if specified value is an appropriatesubstring of requested variable.

messagesNotPresent

Generate the nested body content of this tag if the specified message is notpresent in this request.

messagesPresentGenerate the nested body content of this tag if the specified message is presentin this request.

notEmptyEvaluate the nested body content of this tag if the requested variable is neither

null nor an empty string.notEqual

Evaluate the nested body content of this tag if the requested variable is notequal to the specified value.

notMatchEvaluate the nested body content of tag if specified value not an appropriatesubstring of requested variable.

notPresentGenerate the nested body content of this tag if the specified value is notpresent in this request.

presentGenerate the nested body content of this tag if the specified value is present inthis request.

redirect Render an HTTP Redirect

Logic Tags Example


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Logic Tags - Example

Template Tags


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Template Tags

The Template tag library contains three

tags: put, get, and insert. Put tags put

content into request scope, which is

retrieved by a get tag in a different JSPpage (the template). That template is

included with the insert tag.

Template Tags


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Template Tags Insert Inserts (includes, actually) a

template. Templates are JSP pages thatinclude parameterized content. That

content comes from put tags that are

children of insert tags.Put Puts content into request scope.

Get Gets the content from request scope

that was put there by a put tag.

Custom Tags


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Custom Tags

Image Broker Link Test

Custom Tags tld File


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Custom Tags tld File

doctype

com.pri.brokertag.ImageBrokerDoctype

value

true

true

Custom Tags Tag Class


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Custom Tags Tag Classpublic class ImageBrokerDoctype extends TagSupport {

private String value = null;

public int doStartTag() throws JspException{

Hashtable ht = null;

String keyword_count = null;

int iCnt = 0;

HttpServletRequest request = (HttpServletRequest)pageContext.getRequest();

ht = (Hashtable) request.getAttribute("keyword_parms");

keyword_count = (String)

request.getAttribute("queryobject_count");

iCnt ++;

ht.put("QueryObject" + iCnt, value);

request.setAttribute("keyword_parms", ht);

request.setAttribute("queryobject_count", new String(new

Integer(iCnt).toString()));

return EVAL_PAGE; }

}


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STRUTS Configuration File

Unit 6

STRUTS Configuration File


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STRUTS Configuration FileThe developer's responsibility is to

create an XML file named struts-config.xml, and place it in the WEB-INF directory of your application. This

format of this document is constrainedby it's definition in "struts-

config_1_0.dtd". The outermost XML

element must be .


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STRUTS Configuration File Inside of the element, there are two important elements

that are used to describe your actions:This section contains your form bean definitions. You use a element for each form bean, which has the following important attributes: name: A unique identifier for this bean, which will be used to

reference it in corresponding action mappings. Usually, this is also thename of the request or session attribute under which this form beanwill be stored.

type: The fully-qualified Java classname of your form bean.This section contains your action definitions. You use an element for each of your actions you would like to define. Each action

element requires the following attributes to be defined: path: The application context-relative path to the action type: The fully qualified java classname of your Action class name: The name of your element to use with this action

Struts-config.xml


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Struts config.xml


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Web Application Descriptor

File

Unit 7


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Web.xml File

The final step in setting up the application isto configure the application deploymentdescriptor (stored in file WEB-INF/web.xml)to include all the Struts components that arerequired. Using the deployment descriptor forthe example application as a guide, we seethat the following entries need to be createdor modified.

Web xml File


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Web.xml File

imagebrokerWeb

action

org.apache.struts.action.ActionServlet

applicationimagebrokerWeb

configWEB-INF/struts-config.xml

Web.xml File - continued


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Web.xml File continued

action

*.do

index.html

Web xml File - continued


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Web.xml File continued

WEB-INF/struts-bean.tld

/WEB-INF/struts-bean.tld

WEB-INF/struts-html.tld

/WEB-INF/struts-html.tld

WEB-INF/struts-logic.tld

/WEB-INF/struts-logic.tld


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Application Resources File

Unit 8

Application.properties File


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Application.properties File

error.cryptvalue.required=You must enter some text.

error.lob.required=You must enter the Line of Business.

error.unitnbr.required=You must enter the Unit Number.

error.onbase_dns.required=You must enter the OnBase DNS.

imagebroker.linkname=Project Refinery, Inc.

imagebroker.title=pri Image Brokerimagebrokerlink.title=pri Image Broker Link Test

imagelocationlist.title=Image Location List

imagelocationdetail.title=Image Location Detail

imagelocationinsert.title=Image Location Insert

errors.header=

errors.footer=


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Resources

Unit 9

Resources


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Resources

Main Struts Web Site http://jakarta.apache.org/struts/index.html

Struts User Guide

http://jakarta.apache.org/struts/userGuide/index.html

Various Struts Resources http://jakarta.apache.org/struts/resources.html

Ted Husted Web Site http://www.husted.com/struts/

Struts Intro Course

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