Web Development with Apache Struts 2

Web Development with
Apache Struts 2

Fabrizio Giudici

Tidalwave sas, CEO
NetBeans Dream Team

Senior Java Architect, Blogger

www.tidalwave.it
bluemarine.tidalwave.it
weblogs.java.net/blog/fabriziogiudici
stoppingdown.net

Nov 20, 2008 Web Development with Apache Struts 2 1

Agenda
● Java Web Frameworks
● Struts basics
● Struts 2
● A small code example
● Q&A


NetBeans 6.5 is out
● Get it while it's hot! www.netbeans.org
– Faster!
– Compile-on-save, multithreading Java
debugger, visual deadlock indication
– PHP support, JavaScript debugger and
library manager, better Spring /
Hibernate / JSF / JPA support
– RESTful web services, SQL editor
improvements, JavaFX, Groovy and
Grails, Ruby and Rails improvements,
GlassFish v3
●

Java Web Frameworks
● Question: how many Java web
frameworks are available?
– 1?
– 5?
– 10?
– Dozens?


Java Web Frameworks
● Answer: more than 50!
– www.manageability.org/blog/stuff/how-
many-java-web-frameworks
● Of course, those with a significant
spread are not so many
● But choosing is difficult
● NIH, but also radically different
approaches


My (subjective) take
● Wicket
– You really want to be agile
– You routinely live on the leading edge
● Tapestry
– You like agile, but consolidated
● Struts
– You are “conservative” and like it easy
● Java Server Faces
– You love visual designers
– You can survive to high complexity

JEE
● JEE Web components:
– “Foundation”: Servlet, JSP, Filter
– “High level”: JSF
● Foundation elements are enough, but
you're going to write tons of code
– Validation, flow control, etc...


Struts
● Struts 1 appeared in June 2001
– Apache License
– Strictly based on MVC pattern
– Supported declarative validation, flow
control
● Struts 2 is the “merge” of Struts 1 +
WebWork


MVC


Struts 2.x benefits
● Actions are POJOs
● Interceptors (from AOP)
● Classes are now independent of HTTP
● Simplified testing
● Annotations, AJAX, Spring, Portlets,
etc...


Workflow


Components
● web.xml
– Installs a Filter on /*
● struts.xml
– Maps Action names
– Defines the navigation flow
● Actions
– Execute a task
● Views (JSP or others)
– Render the UI

web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app ... >
<filter>
<filter-name>struts2</filter-name>
<filter-class>
org.apache.struts2.dispatcher.FilterDispatcher
</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

...

</web-app>


A simple Action
import com.opensymphony.xwork2.ActionSupport;

public class MyAction extends ActionSupport {
private final List<String> NBDTers = Arrays.asList(...);

private String userName;
private String message;

public String getUserName() { return userName; }

public void setUserName(String userName) {
this.userName = userName;
}

public String getMessage() { return message; }

@Override
public String execute() {
message = userName;
return NBDTers.contains(userName) ? "nbdt" : SUCCESS;
}
}

struts.xml

<struts>

<package name="/" extends="struts-default">
<action name="MyAction" class="myexample.MyAction">
<result name="input">/index.jsp</result>
<result name="success">/good.jsp</result>
<result name="nbdt">/nbdt.jsp</result>
</action>
</package>

</struts>


A simple view JSP
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@taglib prefix="s" uri="/struts-tags" %>

<html>
<body>
<h2>Welcome to JUG Lugano</h2>
Hello, <s:property value="message" default="Guest" />,
welcome to the first meeting of JUG Lugano!
<s:form method="GET" action="MyAction.action">
Would you be so kind to tell me your name?
<s:textfield name="userName" />
<s:submit value="Submit" />
</s:form>

<s:actionerror/>
<s:fielderror/>
</body>
</html>


Interceptors
● Used to implement “common”
behaviours
– Validations
– Multiple submit filters
– Logging
● Pre-defined interceptors


Formal validation
● Declarative, save tons of code

<validators>

<field name="userName">
<field-validator type="requiredstring">
<param name="trim">true</param>
<message>Your name is required.</message>
</field-validator>
</field>

</validators>


Interceptors
● Code that is invoked across Actions
● Many pre-defined interceptors
– Parameter rename, cookie
management, component behaviours
(e.g. Checkboxes), background
actions
– Validation itself is an interceptor


Custom interceptors

public interface Interceptor
extends Serializable
{
public void destroy();

public void init();

public String intercept (ActionInvocation inv)
throws Exception;
}


Interceptors in
struts.xml

<struts>

<package name="/" extends="struts-default">
<interceptors>
<interceptor name="logger" class="..."/>
</interceptors>
<action name="MyAction" class="myexample.MyAction">
<interceptor-ref name="logger"/>
<result name="success">/good.jsp</result>
<result name="nbdt">/nbdt.jsp</result>
<result name="input">/index.jsp</result>
</action>
</package>

</struts>


Conclusion
● Robust, Struts 1 heritage
● Keeps up with the latest standards
(POJOs, AOP, annotations, Spring, ...)
● “Conservative” approach, but easy
● Relevant sites:
– struts.apache.org
– beans.seartipy.com/2008/08/04/struts-
2-plugin-for-netbeans-ide-
nbstruts2support/


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