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Advanced Struts

In this presentation, we are going to talk about advanced featuresof Struts. I expect the audience of this presentation has some basicunderstanding on Struts.

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Sang Shin

[email protected]

Java Technology EvangelistSun Microsystems, Inc.

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Disclaimer & Acknowledgments

? Even though Sang Shin is a full-time employee of Sun

Microsystems, the content in this presentation is created as hisown personal endeavor and thus does not reflect any officialstance of Sun Microsystems.

? Sun Microsystems is not responsible for any inaccuracies in thecontents.

? Acknowledgments:

I borrowed from presentation slides from the following sources? Using the Struts framework presentation material from Sue Spielman of

Switchback Software ([email protected])

Struts' user's guide is also used in creating slides and speaker notes

Source code examples are from Cookbook example originally written by

I also used Programming Jakarta Struts book written by Chuck Cavaness

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Revision History

? 12/01/2003: version 1: created by Sang Shin? 04/09/2004: version 2: speaker notes are polished a bit? 09/01/2005: DynaActionForm and Validation Framework

slides are separated out into a different file? Things to do

speaker notes need to be added

more example codes need to be added

javascript slides need to be added

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Advanced Struts Topics

? Extending & customizing Struts framework Plug-In API (1.1)

? ForwardAction (1.1)? DispatchAction (1.1)? Declarative exception handling (1.1)

? Multiple application modules support (1.1)

So this is the first page of the topics we will discuss in this presentation. First,

we will talk about how to extend and customize Struts framework especiallywith plug-in mechanism. Then we will talk about DynaActionForm. We will

spend quite a bit of our time talking about Validation and Tiles frameworks.

Validation framework enables validation through configuration. And Tilesframework enables a flexible way of managing layouts. We will talk a bit on

declarative exception handling. And then we will talk about how multipleapplication modules can be configured. As you can see all of these features

are introduced in Struts 1.1.

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Advanced Struts Topics

? Struts and security

? Struts utility classes

? Nested tag library

? Differences between Struts 1.0 and 1.1

? Roadmap

We will then talk about how to use Struts to access databases. We will also

talk about how expression language feature of JSTL can be used with Struts.We will spend a bit of time taking about how security features such as SSL can

be used with Struts. Then we will talk about a few other issues.

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Advanced Struts Topics Covered

in Other Presentations? Struts Tags

? Struts Validation Frameworks

? Struts and Tiles

? Struts and Database Access? Struts Best Practices? Struts Tools

.

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Extending &Customizing

Struts Framework

N ow let's talk about how to extend and customize Strutsframework especially plugin mechanism. We are talking aboutthis topic first because the plugin mechanism is going to be usedby Validator and Tiles frameworks.

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Extending Struts Framework

? Struts framework is designed withextension and customization in mind It provides extension hooks

Validator and Tiles use these extension hooks

? Extend the framework only ifdefaultsetting does not meet your needs There is no guarantee on the backward

compatibility in future version of Struts if you areusing the extension

One of the reasons why Struts has become such a popular framework is itallows extension and customization in pretty much every facet of its

framework. In fact, one of the original design goals of Struts isextensibility and customizability. So it is designed with these aspects inmind and as you will see in the following slides, it provides variousextension hooks in its architecture. In fact, several features of Struts suchas Validator and Tiles use these extensions underneath.

Now Struts framework comes with lots of built-in features so in mostcases you do not need to extend and customize the framework. And when

you have to, it is recommended that you do it with care because there is noguarantee that your application will work with the next version of theStruts framework.

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Extension/Customization

Mechanisms of the Framework

? Plug-in mechanism (1.1)

? Extending framework classes (1.1) Extending Struts configuration classes

ExtendingActionServlet class

Extending RequestProcessorclass

ExtendingAction class

? Using multiple configuration files (1.1)

So the primary extension mechanism of Struts is plug-in mechanism,which was introduced as part of Struts 1.1.

In addition, you can also extend the framework classes. Again, this is notnecessary for most applications.

We will then talk about how you can use DispatchAction class. Also we

will talk about how you can use multiple configuration files.

By the way, all of these features are introduced in Struts 1.1.

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Extension/Customization:

Plug-in Mechanism

So let's talk about plugin mechanism first.

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What is a Plug-in?

? Any Java class that you want to initialize

when Struts application starts up anddestroy when the application shuts down Any Java class that implements

org.apache.struts.action.Plugin interface

public interface PlugIn {

public void init(ActionServlet servlet,

ApplicationConfig config)

throws ServletException;

public void destroy();

}

A plugin under Struts context is basically any Java class that implementsorg.apache.struts.action.Plugin interface. As you can see in the slide, the

Plugin interface has init(..) anddestroy()methods, which are used for one-timeinitialization and cleanup respectively. The initialization occurs when Strutsapplication gets started up and the cleanupoccurs when the application is beingshut down. So inside the init() method, for example, you might want to create adatabase connection, and inside the destroy() method, you might want to closethe database connection.

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Why Plug-in?

? Before Struts 1.1 (in Struts 1.0), you had to

subclassActionServlet to initializeapplication resources at startup time

? With plugin mechanism (in Struts 1.1), youcreate Plugin classes and configure them

? Generic mechanism Struts framework itself uses plugin mechanism for

supporting Validator and Tiles

So why do we need plugin mechanism? Before plugin is introduced, that isunder Struts 1.0, the only way you can do some initialization is to subclassActionServlet class. Obviously this is not really a convenient way of performingan initialization.

With plugin mechanism, you create plugin classes and then configure themthrough struts-config.xml file. So, as was mentioned, Struts framework itselfuses plugin mechanism for adding validator and tiles frameworks.

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How do you configure Plug-in's?

? Must be declared in struts-config.xml via

element? 3 example plug-in's in struts-example sample

application

Struts PlugIns are configured using the element within the Strutsconfiguration file. This element has only one valid attribute, 'className', whichis the fully qualified name of the Java class which implements theorg.apache.struts.action.PlugIn interface.

For PlugIns that require configuration themselves, the nested element is available.

So this slide shows three elements in the struts-config.xml file of thestruts-examples1 sample code that you find in the hands-on lab/homework

material you download from the class website.

The first plugin is ModuleConfigVerifier that verifies module configuration.This plugin comes with Struts. The second is MemoryDatabasePlugin thatprovides in-memory SQL database functionality and the third one is Validator

plugin.

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How do Plug-in's get called?

? During startup of a Struts application,

ActionServlet calls init() method of eachPlug-in configured

? Plug-ins are called in the order they areconfigured in struts-config.xml file

So how do these plugin's get called? During the startup of a Struts applicatiuon,ActionServlet calls init() method of each plugin configured. And these pluginsare called in the order they are configured in the struts-config.xml. So if theorder of initialization is important, make sure they are configured in the rightorder.

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init() of MemoryDatabasePlugin instruts-example sample application

public final classMemoryDatabasePlugIn implements PlugIn {

.../*** Initialize and load our initial database from persistent storage.** @param servlet The ActionServlet for this web application* @param config The ApplicationConfig for our owning module** @exception ServletException if we cannot configure ourselves correctly*/

public void init(ActionServlet servlet, ModuleConfig config)throws ServletException {

log.info("Initializing memory database plug in from '" +pathname + "'");

// Remember our associated configuration and servletthis.config = config;this.servlet = servlet;

This is code fragment from the MemoryDatabasePlugin code that comes withstruts-example1 sample code you download from the class website.

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Continued...

// Construct a new database and make it availabledatabase = new MemoryUserDatabase();try {

String path = calculatePath();if (log.isDebugEnabled()) {

log.debug(" Loading database from '" + path + "'");}database.setPathname(path);database.open();

} catch (Exception e) {log.error("Opening memory database", e);throw new ServletException("Cannot load database from '" +

pathname + "'", e);}

// Make the initialized database availableservlet.getServletContext().setAttribute(Constants.DATABASE_KEY,

database);

// Setup and cache other required datasetupCache(servlet, config);

}

This is the continuation of the init() method of the plugin.

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destroy() of MemoryDatabasePlugin instruts-example1 sample code

public final classMemoryDatabasePlugIn implements PlugIn {.../*** Gracefully shut down this database, releasing any resources* that were allocated at initialization.*/

public void destroy() {

log.info("Finalizing memory database plug in");

if (database != null) {try {

database.close();} catch (Exception e) {

log.error("Closing memory database", e);

}}

servlet.getServletContext().removeAttribute(Constants.DATABASE_KEY);database = null;

servlet = null;database = null;config = null;

This is the code fragment of the MemoryDatabasePlugin which shows thedestroy() method.

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Extending StrutsFramework Classes

OK. we just took a look at the plug-in mechanism. Now let's see how you canextend Struts framework classes. Again, as was mentioned before, in mostcases, you do not need to extend Framework classes.

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Extending Configuration Classes

? org.apache.struts.config package contains

all the classes that are in-memoryrepresentations of all configurationinformation in struts-config.xml file ActionConfig, ActionMapping, ExceptionConfig,

PluginConfig, MessageResourcesConfig,ControllerConfig, DataSourceConfig,FormBeanConfig, etc

? You extend these classes and then specifythe extended class with class nameattribute in struts-config.xml

Under Struts 1.1, all the configuration information specified in the struts-config.xml file is internally represented by various configuration classes. Andall these classes are in the org.apache.struts.config package. And the aboveslide shows all these configuration classes. And I assume you might be alreadyfamiliar with ActionMapping or FormBeanConfig classes.

Now you can extend (subclass) these classes and then specify them in theappropriate place in the struts-config.xml file where class file name can bespecified.

So let's take a look at a few cases where some of these classes can be extendedand then configured.

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Extending ActionServlet Class

? In Struts 1.0, it is common to extend

ActionServlet class since There was no plugin mechanism

ActionServlet handles all the controller functionalitysince there was no RequestProcessor

? Rarely needed in Struts 1.1? Change web.xml

action

myPackage.myActionServlet

First, let's take a look at a case where you can extend ActionServlet class. Aswas mentioned before, in Struts 1.0 where there was no plugin mechanism,extending ActionServlet class was a common practice. In Struts 1.1, in whichwe now have plugin mechanism and introduction of RequestProcessor class, it israre that you have to extend ActionServlet class.

In case you have to, basically the way you can provide your own customizedActionServlet class is to extend the ActionServlet, let's call it myActionServlet,and then configure it in the web.xml as shown above.

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Extending RequestProcessor Class

? Via element in struts-config.xml

? process() method ofRequestProcessorclass iscalled beforeActionForm class is initialized andexecute() method ofAction object get called

? Example in struts-cookbook sample code

RequestProcessor class was introduced in Struts 1.1 and it took over much of thefunctionality that ActionServlet does in Struts 1.0. The process() method ofRequestProcssor class gets called before ActionForm class is initialized andbefore calling execute() method of Action object.

Since process() method of RequestProcessor class gets called internally byActionServlet, normally, you don't have to worry about this class. Now if youwant to extend it, then you have to do it by explicitly specifying element as mentioned above.

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Extending Action Classes

? Useful to create a base Action class when

common logic is shared among manyAction classes

Create base Action class first then subclass it foractual Action classes

Now let's see how we can extend Action class. Extending Action class can beuseful when you have to create many Action classes and these Action classesshare common logic. In that case, what you can do is to create a base Actionclass then subclass it for actual Action classes.

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Using MultipleStruts Configuration File

Now let's talk about how you can use multiple Struts configuration files.

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Multiple Configuration Files

? Useful for multi-developer environment At least, a single struts-config.xml file is not a

bottleneck anymore

? Different from Multiple modules support

Being able to use multiple Struts configuration files in a multi-developerenvironment is useful since Struts configuration file is no longer a bottleneck.

Please note that this is a different feature from multiple modules supportwhich we will talk about later on.

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web.xml of struts-example

actionorg.apache.struts.action.ActionServlet

config

/WEB-INF/struts-config.xml,/WEB-INF/struts-config-registration.xml

1

So how do you let Struts framework know that you have multiple con figurationfiles? Basically you provide common separated configuration fikles as .

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struts-config-registration.xml ofstruts-example sample app


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struts-config-registration.xml ofstruts-example

This slide shows element.

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ForwardAction


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Why ForwardAction?

? If you have the case where you don't need to

perform any logic in the Action but would liketo follow the convention of going through an

Action to access a JSP, the ForwardActioncan save you from creating many empty

Action classes? You don't have to create an Action class

All you have to do is to declaratively configure anAction mapping in your Struts configuration file.

There are probably many cases in your application where you want an Action tojust forward to a JSP. In fact, the previous tip stated that it's good practice toalways front a JSP with an Action. If you have the case where you don't need toperform any logic in the Action but would like to follow the convention ofgoing through an Action to access a JSP, the ForwardAction can save you fromcreating many empty Action classes. The benefit of the ForwardAction is thatyou don't have to create an Action class of your own. All you have to do is to

declaratively configure an Action mapping in your Struts configuration file.

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Example: ForwardAction

? Suppose that you had a JSP page called

index.jsp and instead of calling this pagedirectly, you would rather have the applicationgo through an Action class

? http://hostname/appname/home.do

For example, suppose that you had a JSP called index.jsp and instead of callingthis page directly, you would rather have the application go through an Actionclass. What you can do is set up an Action mapping like this:

When the home action is invoked, the ForwardAction performs a forward to the

index.jsp page.

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Example: ForwardAction

? Another way for forwarding

While we are discussing forwarding without having to provide an Action class,it should also be mentioned that you could also use the forward attribute of the element to achieve the same behavior. The element wouldlook like this:

Both approaches save you time and help to reduce the number of files needed

by an application.

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Why ForwardAction?

? You can also prevent direct access to a

JSP page Move your JSP page under /WEB-INF

Use ForwardAction

Another reason you might want to ue ForwardAction is to prevent direct accessto a JSP page by an end-user mostly due to security reasons. You can move theJSP page under WEB-INF directory and then use ForwardAction. Please notethat anything under WEB-INF directory cannot be directly addressable by anend-user.

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Why ForwardAction?? Aligned with Model 2 MVC design pattern

? If you are using , you are not usingModel 2 MVC (dispatching is done inside JSPpage)Top page

? If you are using ForwardAction, you are using

Model 2 MVC

.

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DispatchAction


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Why DispatchAction?

? To allow multiple related operations to

reside in a single Action class Instead of being spread over multiple Action

classes

? To allow common logic to be shared Related operations typically share some common

business logic

What is the motivation of using DispatchAction class? DispatchAction classallows mutliple related operations to reside in a single Action class instead ofbeing spread over multiple Action classes. It also allows common logic to beshared among these operations since these related operations typically sharesome common business logic.

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How to use DispatchAction?

? Create a class that extends DispatchAction

(instead ofAction)? In a new class, add a method for every

function you need to perform on the service The method has the same signature as the

execute() method of an Action class

? Do not override execute() method Because DispatchAction class itself provides

execute() method

? Add an entry to struts-config.xml

So how do you use DispatchAction? First you create a class that extendsDispatchAction class and then add a method for every function you need toperform on the service. These methods should receive same set of parametersand types as a typical execute() method of an Action class. And because execute()method is provided by the DispatchAction class itself, you should not overridethe execuite() method. Finally you would need an entry to the struts-config.xmlfile.

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Example: ItemAction class extendsDispatchAction

public class ItemActionextends DispatchAction {

public ActionForward addItem(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response) throws Exception {

try {// Code for item add

} catch(Exception ex) {//exception}}

public ActionForward deleteItem(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response) throws

Exception {try {

// Code for item deletion}catch(Exception ex){//exception}

}}

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Example: struts-config.xml

The method can be invoked using a URL, like this:ItemAction.do?actionType=addItem

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Example: How To Use it

? Using URL: Invoke it using a URL

ItemAction.do?actionType=addItem? From JSP page

Save

Remove

.

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DeclarativeException Handling

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Why Declarative Exception Handling?

? Previously (Struts 1.0), Action class has to

deal with all business logic exceptions itself No common exception handling

Rather difficult to implement

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What is Declarative Exception Handling?

? Exception handling policy is declaratively

specified in struts-config.xml Exceptions that may occur

What to do if exceptions occur

? Can be global and per-Action From a particular Exception class or super class

To an application-relative path

? Requires a small change to your Action toleverage this feature ...

/ /

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Example in struts-example

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How Does it Work?

? When an Exception is thrown inside execute()ofActionclass, processException() method ofRequestProcessorclass is called

? processException() method checks if element is configured for thatspecific exception type

? If there is, Default exception handler creates and stores an

ActionErrorinto the specified scope

Control is then forwarded to the resource specifiedin path attribute

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Example in struts-example1

public ActionForwardexecute

(ActionMapping mapping,

ActionForm form,

HttpServletRequest request,

HttpServletResponse response)

throws Exception {

...

throw new PasswordExpiredException(...);

...

}

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Customizing Exception Handling

? Create a class that extendsorg.apache.struts.action.ExceptionHandler

Override execute() method

public ActionForward execute( Exception ex,

ExceptionConfig exConfig,

ActionMapping mapping,

ActionForm formInstance,

HttpServletRequest request,

HttpServletResponse response

) throws ServletException;

To install your customized exception handler, the first step is to create a class thatextends org.apache.struts.action.ExceptionHandler. There are two methods that you

can override, execute() and storeException(). In most cases, however, you will justneed to override the execute() method. The signature for the execute() method in theExceptionHandler class is shown here:

public ActionForward execute( Exception ex,

ExceptionConfig exConfig,ActionMapping mapping,ActionForm formInstance,HttpServletRequest request,

HttpServletResponse response) throws ServletException;

The method takes in several arguments, including the original exception, andreturns an ActionForward object, which directs the controller as to where therequest should be forwarded after the exception is dealt with.

You can perform whatever behavior you like, but generally you should inspect theexception that was thrown and do something based on the type of exception. Again,the default behavior is to create an error message and forward to the resourcespecified in the configuration file. An example of why you would want or need tocustomize this functionality is to support nested exceptions. Suppose the exception

contained nested exceptions, and those exceptions also may contain otherexceptions. You would need to override the execute() method to create errormessages for each of these.

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? Configure the Custom Exception Handler(globally or per action basis)

Once you have created your specialized ExceptionHandler class, you will needto inform the Struts framework to use your version instead of the default Strutsexception handler. To do this, you will just need to declare your class in theStruts configuration file; this is the declarative part.

You can configure your ExceptionHandler to be used by certain Actionmappings or by all Actions. For specific Action mappings, you include an

element inside of the element. To utilize theExceptionHandler for all Action mappings, you can specify it inside the element. For example, suppose we want to use a customizedexception handler called CustomizedExceptionHandler for all Action mappings.The element might look like this:

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? Multiple Custom Exception Handlers

You can have different exception handlers for different exceptions. In theexample above, the CustomizedExceptionHandler was configured to processany exceptions that were children of java.lang.Exception. However, you cancreate multiple exception handlers, each one worrying about different exceptiontrees. The following XML fragment shows how this can be configured:

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Application Modules

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What are Application Modules?? Allows a single Struts application to be split

into multiple modules Each module has its own Struts configuration file,

JSP pages, Actions

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Multiple Application ModuleSupport

? Necessary for large scale applications Allows parallel development

? Design goals: Support multiple independent Struts configuration

files in the same application

Modules are identified by an "application prefix"that follows the context path

Existing Struts-based applications should be ableto be installed individually, or as a sub-application,with no changes to the pages, Actions, formbeans, or other code

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Multiple Application Modules Support

? Implications of the design goals:

"Default" sub-application with a zero-length prefix(like the ROOT context in Tomcat)

"Context-relative" paths must now be treated as"sub-application-relative"

ActionServlet initialization parameters migrate tothe Struts configuration file

Controller must identify the relevant sub-application, and make its resources available (asrequest attributes)

APIs must be reviewed for assumptions aboutthere being (for example) only one set ofActionMappings

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Application Modules:How to configure

modules

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How to set up and use multipleApplication Modules?

? Prepare a config file for each module.? Inform the controller of your module.

? Use actions to refer to your pages.

Very little is required in order to start taking advantage of the Struts applicationmodule feature. Just go through the following steps:

1. Prepare a config file for each module.2. Inform the controller of your module.3. Use actions to refer to your pages.

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Informing the Controller

?

In web.xml...

config/WEB-INF/conf/struts-default.xml

config/module1 /WEB-INF/conf/struts-module1.xml

...

In struts 1.0, you listed your configuration file as an initialization parameter to the actionservlet in web.xml. This is still done in 1.1, but it's augmented a little. In order to tell theStruts machinery about your different modules, you specify multiple config initializationparameters, with a slight twist. You'll still use "config" to tell the action servlet about your

"default" module, however, for each additional module, you will list an initializationparameter named "config/module", where module is the name of your module (this gets usedwhen determining which URIs fall under a given module, so choose something meaningful!).For example:

...

config/WEB-INF/conf/struts-default.xml

config/module1/WEB-INF/conf/struts-module1.xml

...

This says I have two modules. One happens to be the "default" module, which has no"/module" in it's name, and one named "module1" (config/module1). I've told the controllerit can find their respective configurations under /WEB-INF/conf (which is where I put all myconfiguration files). Pretty simple!

(My struts-default.xml would be equivalent to what most folks call struts-config.xml. I justlike the symmetry of having all my Struts module files being named struts-.xml)

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Application Modules:How to switch modules

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Methods for Switching Modules

? Two basic methods to switching from onemodule to another Use a forward (global or local) and specify the

contextRelativeattribute with a value oftrue

Use the built-inorg.apache.struts.actions.SwitchAction

There are two basic methods to switching from one module to another. You caneither use a forward (global or local) and specify the contextRelative attribute with avalue of true, or you can use the built-in org.apache.struts.actions.SwitchAction .

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Global Forward...

...

......

Here's an example of a global forward:

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Local Forward...

......

......

You could do the same thing with a local forward declared in an ActionMapping:

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org.apache.struts.actions.SwitchAction

...

......

Finally, you could use org.apache.struts.actions.SwitchAction .

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How to change module? To change module, use URI

http://localhost:8080/toModule.do?prefix=/moduleB&page=/index.do

? If you are using the "default" module as wellas "named" modules (like "/moduleB"), youcan switch back to the "default" modulewith a URI http://localhost:8080/toModule.do?prefix=&page=/i

ndex.do

There are two basic methods to switching from one module to another. You caneither use a forward (global or local) and specify the contextRelative attribute with avalue of true, or you can use the built-in org.apache.struts.actions.SwitchAction .

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Struts &Security

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Security

? Struts 1.1 and later offers direct support forthe standard Java Authentication andAuthorization Service (JAAS)

? You can now specify security roles on anaction-by-action basis

While Struts can work with any approach to user authentication andauthorization, Struts 1.1 and later offers direct support for the standard JavaAuthentication and Authorization Service (JAAS). You can now specify securityroles on an action-by-action basis.

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SSL Extension (sslext)

? Extension to Struts 1.1

http://sslext.sourceforge.net

? Extends theActionConfig class,RequestProcessor, and Plugin classes todefine a framework where developers mayspecify the transmission protocol behavior forStruts applications

? Within the Struts configuration file, developersspecify which action requests require HTTPStransmission and which should use HTTP

An extension to Struts 1.1, named sslext, helps solve many of these issues forStruts developers. It extends the ActionConfig class, RequestProcessor, andPlugin classes to define a framework where developers may specify thetransmission protocol behavior for Struts applications. Within the Struts

configuration file, developers specify which action requests require HTTPStransmission and which should use HTTP. Developers can also specify whether toredirect "improperly-protocoled" requests to the correct protocol.

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SSL Extension (sslext)

? Can also specify whether to redirect"improperly-protocoled" requests to the correct

protocol? and tag extension

Struts actions specified in either of these tags areanalyzed to determine the protocol that should beused in requesting that action

The HTML generated by these tags will specify theproper protocol

Developers can also specify whether to redirect "improperly-protocoled" requeststo the correct protocol.

In addition to these extensions, the and the tags have

been extended. In these extensions, the Struts actions specified in either of thesetags are analyzed to determine the protocol that should be used in requesting thataction. The HTML generated by these tags will specify the proper protocol. Anadditional custom tag is defined for allowing users to specify the transmissionprotocol for an individual JSP. This is most often used for form-basedauthentication pages.

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Commons:DynaBeans

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COMMONS-BEANUTILS

? Pluggable type converters

? Mapped properties contact.phone(Work)

? DynaBeans Transparently supported by BeanUtils and

PropertyUtils

The Bean Introspection Utilities component of the Jakarta Commons subprojectoffers low-level utility classes that assist in getting and setting property values

on Java classes that follow the naming design patterns outlined in the JavaBeansSpecification, as well as mechanisms for dynamically defining and accessingbean properties.

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Commons-Beanutils --DynaBeans

public interface DynaBean {

public Object get(String name);

public Object get(String name, int index);

public Object get(String name, String key);

public void set(String name, Object value);

public void set(String name, int index, Objectvalue);

public void set(String name, String key,Object value);

}

DynaBeans combine the extensibility of JavaBeans with the flexibility of aMap. Defining even the simplest JavaBean requires defining a new class andcoding a field and two methods for each property. The properties of a DynaBeancan be configured via an XML descriptor. The virtual properties of a DynaBean

can't be called by standard Java methods, but work well with components thatrely on reflection and introspection.

In a Struts application, you can use DynaBeans to describe your HTML forms.This strategy can avoid creating a formal JavaBean subclass to store a fewsimple properties.

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Struts Utilities

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Utilities?

org.apache.struts.util package? Families of classes that solve common

web app problems.? Suitable for general Java programming

and are worth checking out? Utilities classes include:

Beans & Properties Collection Classes JDBC connection pool Message Resources

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Utility Classes

? common-*.jar Now required for Struts Might require some package renaming for 1.0.2 Struts

apps? Many utilities are now located in the Jakarta

Commons project http://jakarta.apache.org/commons/

BeanUtils Package org.apache.commons.beanutils

Collections Package org.apache.commons.collections

Digester Package org.apache.commons.digester

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BeanUtil & PropertyUtil

? Relies on using Java Reflection tomanipulate Java Beans

? Used throughout Struts (IteratorTag,WriteTag)

? Need to make sure you have a valid bean! Null constructor

Public class declaration

Mutator/Accessor methods

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XML Parsing

? Digester package provides for rules-basedprocessing of arbitrary XML documents.

? Higher level, more developer-friendlyinterface to SAX events

? Digester automatically navigates the elementhierarchy of the XML document Element Matching Patterns Processing Rule

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Struts andJ2EE Patterns

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Struts and Core J2EE Patterns

Client

Action

ServletAction

Action

Forward

Action

FormJSP View

Request

Response

uses

ControllerModel

View Helper

View

ActionMapping

(xml)

Service

Interface

Business

Service

Business

Delegate

Service

Locator

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Struts and Core J2EE Patterns

Composite View

Front Controller Business Delegate

Compsite Entity

DataTransfer Object

Session Facade

DataTransfer Object

Presen tation Re qu estCon troll er Create Accou ntDispatch e r UserA ccoun tManage rDe le gate

EJBSessionBean

UserAccountManagerEJB

EJBEntityBeanUserAccountEJB

EJBEntityBean

CreditCardEJB

CreditCardValuesUserAccountValues

ServerPagetemplate.jsp

ServerPagemenu.jsp

JSPInclude

+ themenu.jsp

ServerPagenew_account.jsp

ServerPagenew_account_confirm.jsp

ActionActionServlet

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Nested Tag Library

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The "Nested" Tag Library

? Brings a nested context to the functionality of

the Struts custom tag library? Written in a layer that extends the current

Struts tags, building on their logic andfunctionality The layer enables the tags to be aware of the tags

which surround them so they can correctly providethe nesting property reference to the Struts system

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The "Nested" Tag Library? Nested tags allow you to establish a default

bean for nested property references

? 1:1 correspondence, and identicalfunctionality, of other Struts tags Except the "name" property gets set for you

automatically ...

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Example: Scenario? Company has many departments

Company bean has a collection of Departmentbeans

? Each department has many employees Department bean has a collection of Employee

beans

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Example: Suppose You WantTo Display the following...

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Example: Using JSTL forIterating Nested Beans

COMPANY:

Department:

Employee:

E-mail:

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Example: Using Nested Tag forDoing the Same ThingCOMPANY:

Department:

Employee:

E-mail:

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Example 2:

? Before using the nested tags:

? After using the nested tags:

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Changes BetweenStruts 1.0 & 1.1

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Struts 1.1 ActionServlet

? Introduction of request processor Via RequestProcessorclass

Handles much of the functionality of ActionServletin Struts1.0

? ActionServlet in 1.1 is a thin layer

Allows developers to customize the requesthandling behavior more easily

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Struts 1.1 Actions

? Method perform() replaced by execute() Backwards compatible

Change necessary to support declarativeexception handling

? Addition ofDispatchAction class Supports multiple business methods instead of a

single execute() method

Allows easy group of related business methods

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Changes to web.xml andstruts-config.xml? web.xml

Serveral initialization parameters removed? Uses elements in struts-config.xml

Supports a few new parameters

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New Features in Struts 1.1

? Plug-ins

? Dynamic ActionForms? Multiple application modules? Declative exception handling? Validator framework? Nested tags? Dependency to Commons projects? Action-based authorization

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Roadmap

I

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New Features in Struts 1.2

? Some deprecations

? Validator enhancements? DigestingPlugin added? MappingDispatchAction added

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Passion!

Documents

24-StrutsAdvanced_93