Building S2 Applications

Building Applications

Struts University Series

Building Applications How are web applications organized? What components does the framework add to the mix? Can traditional architectures be applied to web applications?

Building Applications Web Application Infrastructure Struts Framework Components Model View Controller Architecture Struts Architecture

Web Applications A web application uses a web site as the front-end to a more typical application. In a web application client data input executes business logic on the server. 

Minnesota State Colleges & Universities 

http://krypton.mnsu.edu/~spiral/eta/glossary/indxGlossOOxml.html

Web Applications Web site 

HTML, HTTP

Web application 

Common Gateway Interface (CGI) Perl  PHP  Active Server Pages / ASP.NET  Java / JavaServer Faces 

Java Web Applications Document Root 

*.html, *.jsp 



JSP tags

WEB-INF (Web Application Infrastructure) 

web.xml (Web Application Deployment Descriptor) 



lib 



Servlets, Filters, Listeners, Security Descriptors *.JAR (Java Archive)

classes 

*.class, *.properties, *.tld (tag library descriptor)

Application Infrastructure

Review In a web application client data input executes ******** ***** on the server. To place a resource on the classpath, you can place it under the ******* folder.

Review In a web application client data input executes business logic on the server. To place a resource on the classpath, you can place it under the classes folder.

Review (1) CGI (2) WEB-INF (3) web.xml (4) JAR (5) TLD

(a) Tag Library Descriptor (b) Java Archive (c) Web Application Infrastructure (d) Computer Gateway Interface (e) Web Application Deployment Descriptor

Review (1) CGI (2) WEB-INF (3) web.xml (4) JAR (5) TLD

(d) Computer Gateway Interface (c) Web Application Infrastructure (e) Web Application Deployment Descriptor (b) Java Archive (a) Tag Library Descriptor

Building Applications Web Application Infrastructure Struts Framework Components Model View Controller Architecture Struts Architecture

Why Frameworks? Code reuse Incremental development Long-term maintenance by a team

Separation of Concerns Don't Repeat Yourself

Why Frameworks? Code reuse Incremental development Long-term maintenance by a team

Separation of Concerns Don't Repeat Yourself

Why Frameworks? Code reuse Incremental development Long-term maintenance by a team

Separation of Concerns Don't Repeat Yourself

Why Frameworks? Code reuse Incremental development Long-term maintenance by a team

Separation of Concerns Don't Repeat Yourself

Why Frameworks? Code reuse Incremental development Long-term maintenance by a team

Separation of Concerns Don't Repeat Yourself

Struts Components Action handler Result handler Custom tags

Struts Components Action handler 

Interacts with other layers

Result handler Custom tags

Struts Components Action handler 

Interacts with other layers

Result handler 

Dispatches to server page, HTML, PDF, ...

Custom tags

Struts Components Action handler 

Interacts with other layers

Result handler 

Dispatches to server page, HTML, PDF, ...

Custom tags 

Render dynamic content

struts.xml <struts> <package name="default" extends="struts-default"> <default-action-ref name="Hello"/> /pages/Hello.jsp

Hello.jsp <%@ taglib prefix="s" uri="/tags" %>

<s:text name="hello.message"/>

resources.properties hello.message = Congratulations! Struts is up and running ... # Add your messages here ...

Hello World!

Welcome.jsp <%@ taglib prefix="s" uri="/tags" %>

Options

• "> Register
• "> Sign On

Pick your Poison!

Review – Why Frameworks? Code re*** In********* development Long-term m********** by a team

********** of Concerns Don't ****** Yourself

Review – Why Frameworks? Code reuse Incremental development Long-term maintenance by a team

Separation of Concerns Don't Repeat Yourself

Review The key framework components are: ****** *******  ****** *******  ****** **** 

The Struts 2 default configuration file is named ******.xml. To reference the Struts taglib, use the URI “*****”.

Review The key framework components are Action handler  Result handler  Custom tags 

The Struts 2 default configuration file is named struts.xml. To reference the Struts 2 taglib, use the URI “/tags”.

Building Applications Web Application Infrastructure Struts Components Model View Controller Architecture Struts Architecture

Model View Controller

Model View Controller

Review (1) Model (2) View (3) Controller

(a) Renders Model (b) Selects View (c) Retains State

Review (1) Model (2) View (3) Controller

(c) Retains State (a) Renders Model (b) Selects View

Struts Architecture Interceptors Value Stack Expression Language

Interceptors: Domain AOP Interceptors allow custom code into the call stack Much of the core functionality of the framework is implemented as Interceptors Custom Interceptors are easy to add

TimerInterceptor TimerInterceptor is the simplest Interceptor Times the execution of the Action public String intercept(ActionInvocation invocation) throws Exception { if (log.isInfoEnabled()) { long startTime = System.currentTimeMillis(); String result = invocation.invoke(); long executionTime = System.currentTimeMillis() - startTime; String namespace = invocation.getProxy().getNamespace(); … }

Preparable public interface Preparable { void prepare() throws Exception; }

protected void intercept(ActionInvocation invocation) throws Exception { Object action = invocation.getAction(); if (action instanceof Preparable) { ... ((Preparable) action).prepare(); ... } } }

Review - Interceptor Interceptors allow custom **** into the request processing pipeline Much of the core ************* of the framework is implemented as Interceptors Custom Interceptors are (hard / easy) to add

Review - Interceptor Interceptors allow custom code into the request processing pipeline Much of the core functionality of the framework is implemented as Interceptors Custom Interceptors are easy to add

Struts Architecture Interceptors Value Stack Expression Language

What is the ValueStack? The ValueStack builds a stack of objects Objects are examined to find property values The ValueStack allows the expression language to find property values across multiple objects

How is the ValueStack used? The Action instance is always pushed onto the ValueStack The Model is pushed on by the ModelDrivenInterceptor The UI tags use it to push values on during their scope and evaluate expressions    

The <s:iterator> tag pushes the current item onto the stack The <s:bean> tag pushes a bean instance on The <s:property> tag evaluates an expression against the ValueStack All tag attribute values are evaluated against the stack when being set onto the tag instances

Review - ValueStack The ValueStack builds a ***** of objects. Objects are examined to find property ******. The ValueStack allows the ********** ******** to find property values across multiple objects.

Review - ValueStack The ValueStack builds a stack of objects Objects are examined to find property values The ValueStack allows the expression language to find property values across multiple objects

Struts Architecture Interceptors Value Stack Expression Language

OGNL Expression Language For expressions, the framework uses OGNL (Object Graph Navigation Language)      

An expression and binding language for getting and setting properties of Java objects Normally the same expression is used for both getting and setting the value of a property Easy to learn, yet powerful Incrementally compiled expressions - fast! Embedded everywhere – views, ValueStack, *.xml Independent Open Source project - http://www.ognl.org

OGNL samples OGNL

Result

user.name

getUser().getName()

user.toString()

getUser().toString()

item.categories[0] @com.example.Test@foo ()

First element of Categories collection Calls the static foo() method on the com.example.Test class

name in {null,”fred”}

True if name is null or “fred”

categories.{name}

Calls getName() on each Category in the collection, returning a new collection (projection)

Review - OGNL OGNL stands for Object Graph ********** Language OGNL is an expression and ******* language for getting and setting properties of Java objects Within the framework, OGNL is ******** everywhere – views, ValueStack, xml configuration files.

Review - OGNL OGNL stands for Object Graph Navigation Language OGNL is an expression and binding language for getting and setting properties of Java objects Within the framework, OGNL is embedded everywhere – views, ValueStack, xml configuration files.

Building Web Applications How are web applications organized? What components does the framework add to the mix? Can traditional architectures be applied to web applications?

Building Web Applications How are web applications organized?  WEB-INF, web.xml, /classes What components does the framework add to the mix? Can traditional architectures be applied to web applications?

Building Web Applications How are web applications organized?  WEB-INF, web.xml, /classes What components does the framework add to the mix?  Actions, Results, Tags Can traditional architectures be applied to web applications?

Building Web Applications How are web applications organized?  WEB-INF, web.xml, /classes What components does the framework add to the mix?  Actions, Results, Tags Can traditional architectures be applied to web applications?  Absolutely!

Struts University Series