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Step By Step Guide For Buidling Simple Struts App Speakernoted
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Step by Step Guide
for building a simple
Struts Application
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In this session, we will try to build a very simple Struts application
step by step.
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Sang Shin
sang.shin@sun.com
www.javapassion.com/j2ee
Java™ Technology Evangelist
Sun Microsystems, Inc.
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Sample App We are
going to build
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Sample App
? Keld Hansen's submit application
? Things to do
– Creating ActionForm object
– Creating Action object
– Forwarding at either success or failure through
configuration set in struts-config.xml file
– Input validation
– Internationalizaition
? You can also build it using NetBeans
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The sample application we are going to use and show is Keld Hansen's
submit application. The source files and ant build.xml script can be found
in the handson/homework material you can download from class website.
This is a simple application but it uses most of Struts framework.
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Steps to follow
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Now let's take a look at the steps you will follow.
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Steps
1.Create development directory structure
2.Write web.xml
3.Write struts-config.xml
4.Write ActionForm classes
5.Write Action classes
6.Create ApplicationResource.properties
7.Write JSP pages
8.Build, deploy, and test the application
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So this is the list of steps. Of course, you don't exactly follow
these steps in sequence. In fact, it is expected that some of these
steps will be reiterated.
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Step 1: Create Development
Directory Structure
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The first step is to create development directory structure.
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Development Directory
Structure
? Same development directory structure for
any typical Web application
? Ant build script should be written
accordingly
? If you are using NetBeans, the
development directory structure is
automatically created
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The source directory structure is the same directory structure we
used for other Web application development under Java WSDP.
Of course, the build.xml script should be written accordingly.
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Step 2: Write web.xml
Deployment Descriptor
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Step 2 is to write web.xml file.
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web.xml
? Same structure as any other Web
application
– ActionServlet is like any other servlet
– Servlet definition and mapping of ActionServlet
needs to be specified in the web.xml
? There are several Struts specific
<init-param> elements
– Location of Struts configuration file
? Struts tag libraries could be defined
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Because Struts application is a genuine Web application, it has
to follow the same rules that any Web application has to follow.
And one of them is the presence of web.xml deployment
descriptor file.
The web.xml file should define ActionServlet, which is the
controller piece that is provided by the Struts framework, and its
mapping with URI.
As you will see in the example web.xml file in the following
slide, there are several Struts specific initialization parameters.
Also the Struts tag libraries also need to be declared.
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Example: web.xml
1 <?xml version=quot;1.0quot; encoding=quot;UTF-8quot;?>
2 <web-app version=quot;2.4quot; xmlns=quot;http://java.sun.com/xml/ns/j2eequot;
xmlns:xsi=quot;http://www.w3.org/2001/XMLSchema-instancequot;
xsi:schemaLocation=quot;http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsdquot;>
3 <servlet>
4 <servlet-name>action</servlet-name>
5 <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
6 <init-param>
7 <param-name>config</param-name>
8 <param-value>/WEB-INF/struts-config.xml</param-value>
9 </init-param>
10 ...
11 </servlet>
12 <servlet-mapping>
13 <servlet-name>action</servlet-name>
14 <url-pattern>*.do</url-pattern>
15 </servlet-mapping>
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This is the continuation of the web.xml file. Here you see the declarations of
Struts tag libraries.
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Step 3: Write
struts-config.xml
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The next step is to write struts-config.xml
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struts-config.xml
? Identify required input forms and then define
them as <form-bean> elements
? Identify required Action's and then define them
as <action> elements within <action-mappings>
element
– make sure same value of name attribute of <form-
bean> is used as the value of name attribute of
<action> element
– define if you want input validation
? Decide view selection logic and specify them as
<forward> element within <action> element
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(read theslide)
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struts-config.xml: <form-beans>
1 <?xml version=quot;1.0quot; encoding=quot;UTF-8quot; ?>
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3 <!DOCTYPE struts-config PUBLIC
4 quot;-//Apache Software Foundation//DTD Struts Configuration 1.2//ENquot;
5 quot;http://jakarta.apache.org/struts/dtds/struts-config_1_2.dtdquot;>
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8 <struts-config>
9 <form-beans>
10 <form-bean name=quot;submitFormquot;
11 type=quot;submit.SubmitFormquot;/>
12 </form-beans>
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This is <form-beans> section of the struts-config.xml file. Here we
define one <form-bean> element. The value of the name attribute of
the <form-bean> element is the same as the value of name attribute of
<action> element in the following slide.
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struts-config.xml:
<action-mappings>
1
2 <!-- ==== Action Mapping Definitions ===============-->
3 <action-mappings>
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5 <action path=quot;/submitquot;
6 type=quot;submit.SubmitActionquot;
7 name=quot;submitFormquot;
8 input=quot;/submit.jspquot;
9 scope=quot;requestquot;
10 validate=quot;truequot;>
11 <forward name=quot;successquot; path=quot;/submit.jspquot;/>
12 <forward name=quot;failurequot; path=quot;/submit.jspquot;/>
13 </action>
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15 </action-mappings>
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This is an example of <action-mappings> element.
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ActionForm Class
? Extend org.apache.struts.action.ActionForm
class
? Decide set of properties that reflect the input
form
? Write getter and setter methods for each
property
? Write validate() method if input validation is
desired
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Write ActionForm class
1 package submit;
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3 import javax.servlet.http.HttpServletRequest;
4 import org.apache.struts.action.*;
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6 public final class SubmitForm extends ActionForm {
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8 /* Last Name */
9 private String lastName = quot;Hansenquot;; // default value
10 public String getLastName() {
11 return (this.lastName);
12 }
13 public void setLastName(String lastName) {
14 this.lastName = lastName;
15 }
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17 /* Address */
18 private String address = null;
19 public String getAddress() {
20 return (this.address);
21 }
22 public void setAddress(String address) {
23 this.address = address;
24 } 18
25 ...
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Write validate() method
1 public final class SubmitForm extends ActionForm {
2
3 ...
4 public ActionErrors validate(ActionMapping mapping,
5 HttpServletRequest request) {
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7 ...
8
9 // Check for mandatory data
10 ActionErrors errors = new ActionErrors();
11 if (lastName == null || lastName.equals(quot;quot;)) {
12 errors.add(quot;Last Namequot;, new ActionError(quot;error.lastNamequot;));
13 }
14 if (address == null || address.equals(quot;quot;)) {
15 errors.add(quot;Addressquot;, new ActionError(quot;error.addressquot;));
16 }
17 if (sex == null || sex.equals(quot;quot;)) {
18 errors.add(quot;Sexquot;, new ActionError(quot;error.sexquot;));
19 }
20 if (age == null || age.equals(quot;quot;)) {
21 errors.add(quot;Agequot;, new ActionError(quot;error.agequot;));
22 }
23 return errors;
When this “LogonForm” is associated with a
24 } 19
25 ..
controller, it will be passed to the controller
whenever it’s service is requested by the
user.
JSP pages acting as the view for this
LogonForm are automatically updated by
Struts with the current values of the
UserName and Password properties.
If the user changes the properties via the JSP
page, the LogonForm will automatically be
updated by Struts
But what if the user screws up and enters
invalid data? ActionForms provide
validation…
Before an ActionForm object is passed to a
controller for processing, a “validate”
method can be implemented on the form
which allows the form to belay processing
until the user fixes invalid input as we will
see on the next slide... 19
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Action Classes
? Extend org.apache.struts.action.Action class
? Handle the request
– Decide what kind of server-side Model objects
(EJB, JDO, etc.) can be invoked
? Based on the outcome, select the next view
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Example: Action Class
1 package submit;
2
3 import javax.servlet.http.*;
4 import org.apache.struts.action.*;
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6 public final class SubmitAction extends Action {
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8 public ActionForward execute(ActionMapping mapping,
9 ActionForm form,
10 HttpServletRequest request,
11 HttpServletResponse response) {
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13 SubmitForm f = (SubmitForm) form; // get the form bean
14 // and take the last name value
15 String lastName = f.getLastName();
16 // Translate the name to upper case
17 //and save it in the request object
18 request.setAttribute(quot;lastNamequot;, lastName.toUpperCase());
19
20 // Forward control to the specified success target
21 return (mapping.findForward(quot;successquot;));
22 }
23 } 22
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Resource file
? Create resource file for default locale
? Create resource files for other locales
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Example:
ApplicationResource.properties
1 errors.header=<h4>Validation Error(s)</h4><ul>
2 errors.footer=</ul><hr>
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4 error.lastName=<li>Enter your last name
5 error.address=<li>Enter your address
6 error.sex=<li>Enter your sex
7 error.age=<li>Enter your age
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