Struts tutorial

Struts Tutorial
MVC Architecture

Struts MVC Architecture
The model contains the business logic and interact with the persistance storage to
store, retrive and manipulate data.
The view is responsible for dispalying the results back to the user. In Struts the
view layer is implemented using JSP.
The controller handles all the request from the user and selects the appropriate
view to return. In Sruts the controller's job is done by the ActionServlet.

The following events happen when the Client browser issues an HTTP request.

The ActionServlet receives the request.
The struts-config.xml file contains the details regarding
the Actions, ActionForms,ActionMappings and ActionForwards.
During the startup the ActionServelet reads the struts-config.xml file and creates a
database of configuration objects. Later while processing the request
the ActionServletmakes decision by refering to this object.

When the ActionServlet receives the request it does the following tasks.

Bundles all the request values into a JavaBean class which extends
Struts ActionForm class.
Decides which action class to invoke to process the request.
Validate the data entered by the user.
The action class process the request with the help of the model component. The
model interacts with the database and process the request.
After completing the request processing the Action class returns
an ActionForward to the controller.
Based on the ActionForward the controller will invoke the appropriate view.
The HTTP response is rendered back to the user by the view component.

Hello World Example in Eclipse
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Struts Tutorial

In this tutorial you will learn how to create a Struts hello world application
in eclipse. First create a new project, go to File->New and select
DynamicWebProject.

Enter the project name and click the Finish button.


Add the following jar files to the WEB-INFlib directory.

Right click the src folder and select New->Package.

Enter the package name as com.vaannila.form and click Finish.
Now right click the newly created package and select New->Class.

Enter the class name as HelloWorldForm and the superclass name
asorg.apache.struts.action.ActionForm and click Finish.


In the HelloWorldForm class add the following code.
01.package com.vaannila.form;
02.
03.import org.apache.struts.action.ActionForm;
04.
05.public class HelloWorldForm extends ActionForm {
06.
07.private static final long serialVersionUID = -473562596852452021L;
08.
09.private String message;
10.
11.public String getMessage() {
12.return message;
13.}
14.
15.public void setMessage(String message) {
16.this.message = message;
17.}
18.}
In the same way create a new package com.vaannila.action and create


a HelloWorldActionclass extending org.apache.struts.action.Action. Add the
following code to the action class and save it.
01.package com.vaannila.action;
02.
03.import javax.servlet.http.HttpServletRequest;
04.import javax.servlet.http.HttpServletResponse;
05.
06.import org.apache.struts.action.Action;
07.import org.apache.struts.action.ActionForm;
08.import org.apache.struts.action.ActionForward;
09.import org.apache.struts.action.ActionMapping;
10.
11.import com.vaannila.form.HelloWorldForm;
12.
13.public class HelloWorldAction extends Action {
14.
15.@Override
16.public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) throwsException
{
17.HelloWorldForm hwForm = (HelloWorldForm) form;
18.hwForm.setMessage("Hello World");
19.return mapping.findForward("success");
20.}
21.}
Here we typecast the ActionForm to HelloWorldForm and set the message
value.
Add the following entries in the struts-config.xml file.
01.<?xml version="1.0" encoding="ISO-8859-1" ?>
02.
03.<!DOCTYPE struts-config PUBLIC
04."-//Apache Software Foundation//DTD Struts Configuration 1.3//EN"
05."http://struts.apache.org/dtds/struts-config_1_3.dtd">
06.
07.<struts-config>
08.
09.<form-beans>
10.<form-
bean name="helloWorldForm"type="com.vaannila.form.HelloWorldForm"/>
11.</form-beans>
12.
13.<global-forwards>
14.<forward name="helloWorld" path="/helloWorld.do"/>
15.</global-forwards>
16.
17.<action-mappings>
18.<action path="/helloWorld"type="com.vaannila.action.HelloWorldAction"n
ame="helloWorldForm">
19.<forward name="success" path="/helloWorld.jsp" />
20.</action>
21.</action-mappings>
22.

23.</struts-config>
Now configure the deployment descriptor. Add the following configuration
information in theweb.xml file.
01.<?xml version="1.0" encoding="UTF-8"?>
02.<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-
instance"xmlns="http://java.sun.com/xml/ns/javaee"xmlns:web="http://jav
a.sun.com/xml/ns/javaee/web-
app_2_5.xsd"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-
app_2_5.xsd" id="WebApp_ID"version="2.5">
03.<display-name>StrutsExample1</display-name>
04.
05.<servlet>
06.<servlet-name>action</servlet-name>
07.<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
08.<init-param>
09.<param-name>config</param-name>
10.<param-value>/WEB-INF/struts-config.xml</param-value>
11.</init-param>
12.<load-on-startup>2</load-on-startup>
13.</servlet>
14.
15.<servlet-mapping>
16.<servlet-name>action</servlet-name>
17.<url-pattern>*.do</url-pattern>
18.</servlet-mapping>
19.
20.<welcome-file-list>
21.<welcome-file>index.jsp</welcome-file>
22.</welcome-file-list>
23.</web-app>
When we run the application the index.jsp page will be executed first. In
the index.jsp page we redirect the request to the helloWorld.do URI, which
inturn invokes the HelloWorldAction.
1.<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
2.<logic:redirect forward="helloWorld"/>
In the action class we return the ActionForward "success" which is mapped
to thehelloWorld.jsp page. In the helloWorld.jsp page we display the "Hello
World" message.
01.<%@taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
02.<html>
03.<head>
04.<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-
1">
05.<title>Hello World</title>
06.</head>
07.<body>
08.<bean:write name="helloWorldForm" property="message"/>
09.</body>
10.</html>
After creating all the files the directory structure of the application looks
like this.

On executing the application the "Hello World" message gets displayed to the
user.

Hello World Application

Lets say a quick hello to struts. Struts follows MVC 2 pattern. The following
files are needed to create a hello world application.

index.jsp
helloWorld.jsp
web.xml
struts-config.xml
HelloWorldAction.java
HelloWorldActionForm.java


web.xml

web.xml is used to configure the servlet container properties of the hello
world appliation.
2.<welcome-file>index.jsp</welcome-file>
The gateway for our hello world application is index.jsp file. The index.jsp file
should be mentioned in web.xml as shown above.
index.jsp

In the hello world example the index.jsp page simply forwards the request to
the hello world action.
1.<jsp:forward page="HelloWorld.do"/>
struts-config.xml

struts-config.xml file is used to configure the struts framework for the hello
world application. This file contains the details regarding the form bean and
the action mapping.
01.<struts-config>
02.

03.<form-beans>
04.<form-bean name="HelloWorldActionForm"
05.type="com.vaannila.HelloWorldActionForm"/>
06.</form-beans>
07.
09.<action input="/index.jsp" name="HelloWorldActionForm"path="/HelloWo
rld" scope="session"type="com.vaannila.HelloWorldAction">
11.</action>
13.
14.</struts-config>
HelloWorldActionForm.java

HelloWorldActionForm extends org.apache.struts.action.ActionForm.
HelloWorldActionForm class has one String variable message and the
corresponding getter and setter methods.
01.public class HelloWorldActionForm extends
02.org.apache.struts.action.ActionForm {
03.
04.private String message;
05.
06.public HelloWorldActionForm() {
07.super();
08.}
09.
10.public String getMessage() {
11.return message;
12.}
13.
14.public void setMessage(String message) {
15.this.message = message;
16.}
17.
18.}
HelloWorldAction.java

HelloWorldAction class extends org.apache.struts.action.Action. The action
class contains an execute method which contains the business logic of the
application. To access the HelloWorldActionForm variables in the Action we
need to type caste the form object to HelloWorldActionForm. Then we can
access the variables using the getter and setter methods. The execute
method returns a value of type ActionForward, based on its value the
corresponding view will be called. This configuration is done in struts-
config.xml file.
01.public class HelloWorldAction extends org.apache.struts.action.Action {
02.
03.private final static String SUCCESS = "success";
04.
05.public ActionForward execute(ActionMapping mapping,ActionForm form,

06.HttpServletRequest request,HttpServletResponse
response)throws Exception {
07.
08.HelloWorldActionForm helloWorldForm = (HelloWorldActionForm) form;
09.helloWorldForm.setMessage("Hello World!");
10.return mapping.findForward(SUCCESS);
11.
12.}
13.}
1.<action-mappings>
2.<action input="/index.jsp" name="HelloWorldActionForm"path="/HelloWorl
d"
3.scope="session" type="com.vaannila.HelloWorldAction">
5.</action>
The name "success" is mapped to the view helloWorld.jsp. So when the
execute method in the action returns "success" the request will be forwarded
to the helloWold.jsp page.
helloWorld.jsp

In helloWorld.jsp we get the value of the form variable message and display
it. We use struts bean tag to do this. The name attribute of the bean tag hold
the value of the action form and the property attribute holds the value of the
variable to be displayed.
01.<%@taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
02.<html>
03.<head>
04.<title>Hello World</title>
05.</head>
06.<body>
07.<h1>
08.<bean:write name="HelloWorldActionForm" property="message" />
09.</h1>
10.</body>
11.</html>
Extract the downloaded files into the webapps folder of the Tomcat server.
Start the Tomcat server. Type the following url in the browser
"http://localhost:8080/Example1/index.jsp". There you go, you have your
first struts program up and running.


Login Application Using Action Form
Login Application Using Action Form

In this example we will see how to create a login application using
ActionForm. The following files are required for the login application.

login.jsp
success.jsp
failure.jsp
web.xml
struts-config.xml
LoginAction.java
LoginForm.java
ApplicationResource.properties

web.xml

The first page that will be called in the login application is the login.jsp page.
This configuration should be done in web.xml as shown below.
2.<welcome-file>login.jsp</welcome-file>
login.jsp

We use Struts HTML Tags to create login page. The form has one text field to
get the user name and one password field to get the password. The form also
has one submit button, which when clicked calls the login
action. <html:errors /> tag is used to display the error messages to the user.
01.<%@taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
02.<html>
03.<head>
04.<title>Login Page</title>
05.</head>


06.<body>
07.<div style="color:red">
08.<html:errors />
09.</div>
10.<html:form action="/Login" >
11.User Name :<html:text name="LoginForm" property="userName" />
12.Password :<html:password name="LoginForm" property="password" />
13.<html:submit value="Login" />
14.</html:form>
15.</body>
16.</html>
The user enters the user name and password and clicks the login button. The
login action is invoked.
struts-config.xml

The validate method in the LoginForm class is called when the Form is
submitted. If any errors are found then the control is returned back to the
input page where the errors are displayed to the user. The input page is
configured in the action tag of strut-config file. <html:errors /> tag is used to
display the errors in the jsp page.
01.<struts-config>
02.<form-beans>
03.<form-bean name="LoginForm" type="com.vaannila.LoginForm"/>
04.</form-beans>
05.
07.<action input="/login.jsp" name="LoginForm" path="/Login"scope="sessio
n" type="com.vaannila.LoginAction">
08.<forward name="success" path="/success.jsp" />
09.<forward name="failure" path="/failure.jsp" />
10.</action>
12.</struts-config>
Here the action is "/Login" , the input page is "login.jsp" and the
corresponding action class is LoginAction.java. Now the validate method in
the LoginForm class will be invoked.

LoginForm.java

Inside the validate method, we check whether the user name and password is
entered. If not the corresponding error message is displayed to the user. The
error messages are configured in the ApplicationResource.properties file.
01.public ActionErrors validate(ActionMapping mapping, HttpServletRequest
request) {
02.ActionErrors errors = new ActionErrors();
03.if (userName == null || userName.length() < 1) {
04.errors.add("userName", newActionMessage("error.userName.required"));
05.}
06.if (password == null || password.length() < 1) {
07.errors.add("password", newActionMessage("error.password.required"));
08.}

09.return errors;
10.}
ApplicationResource.properties

The ApplicationResource.properties file contains the error messages. The key
"error.userName.required" is used in the validate function to add a new error.
Since the error messages are configured in a seperate properties file they can
be changed anytime without making any changes to the java files or the jsp
pages.

1.error.userName.required = User Name is required.
2.error.password.required = Password is required.
If either user name or password is not entered then the corresponding error
message will be added to the ActionErrors. If any errors are found then the
control is returned back to the input jsp page, where the error messages are
displayed using the <html:errors /> tag. The validate method is used to
perform the client-side validations. Once when the input data is valid the
execute method in the LoginAction class is called.
LoginAction.java

The execute method contains the business logic of the application. Here first
we typecast the ActionForm object to LoginForm, so that we can access the
form variables using the getter and setter methods. If the user name and
password is same then we forward the user to the success page else we
forward to the failure page.
01.public class LoginAction extends org.apache.struts.action.Action {
02.
04.private final static String FAILURE = "failure";
05.
06.public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) throwsException
{
07.LoginForm loginForm = (LoginForm) form;
08.if (loginForm.getUserName().equals(loginForm.getPassword())) {
10.} else {
11.return mapping.findForward(FAILURE);
12.}
13.}
14.}
Lets enter the user names and password as "Eswar". Since the user name and
password is same the execute method will return an ActionForward
"success". The corresponding result associated with the name "success" will
be shown to the user. This configuration is done in struts-config.xml file.

1.<action-mappings>
2.<action input="/login.jsp" name="LoginForm" path="/Login"scope="session"
type="com.vaannila.LoginAction">
3.<forward name="success" path="/success.jsp" />


4.<forward name="failure" path="/failure.jsp" />
5.</action>
So according to the configuration in struts-config.xml the user will be
forwarded to success.jsp page.

If the user name and password did not match the user will be forwarded to
the failure page. Lets try entering "Joe" as the user name and "Eswar" as the
password, the following page will be displayed to the user.


DispatchAction Class
DispatchAction Class
DispatchAction provides a mechanism for grouping a set of related functions
into a single action, thus eliminating the need to create seperate actions for
each functions. In this example we will see how to group a set of user related
actions like add user, update user and delete user into a single action called
UserAction.
The class UserAction extends org.apache.struts.actions.DispatchAction. This
class does not provide an implementation of the execute() method as the
normal Action class does. The DispatchAction uses the execute method to
manage delegating the request to the individual methods based on the
incoming request parameter. For example if the incoming parameter is
"method=add", then the add method will be invoked. These methods should
have similar signature as the execute method.
01.public class UserAction extends DispatchAction {
02.
04.
05.public ActionForward add(ActionMapping mapping, ActionForm form,
06.HttpServletRequest request, HttpServletResponse response)
07.throws Exception {
08.UserForm userForm = (UserForm) form;
09.userForm.setMessage("Inside add user method.");
11.}
12.
13.public ActionForward update(ActionMapping mapping, ActionForm form,
17.userForm.setMessage("Inside update user method.");
19.}
20.
21.public ActionForward delete(ActionMapping mapping, ActionForm form,

25.userForm.setMessage("Inside delete user method.");
27.}
28.}
If you notice the signature of the add, update and delete methods are similar
to the execute method except the name. The next step is to create an action
mapping for this action handler. The request parameter name is specified
using the parameter attribute. Here the request parameter name is method.
1.<action-mappings>
2.<action input="/index.jsp" parameter="method" name="UserForm"path="/U
serAction" scope="session" type="com.vaannila.UserAction">
3.<forward name="success" path="/index.jsp" />
4.</action>
Now lets see how to invoke a DispatchAction from jsp. We have a simple form
with three buttons to add, update and delete a user. When each button is
clicked a different method in UserAction class is invoked.
01.<html>
02.<head>
03.<script type="text/javascript">
04.function submitForm()
05.{
06.document.forms[0].action = "UserAction.do?method=add"
07.document.forms[0].submit();
08.}
09.</script>
10.</head>
11.<body>
12.<html:form action="UserAction" >
13.<table>
14.<tr>
15.<td>
16.<bean:write name="UserForm" property="message" />
17.</td>
18.</tr>
19.<tr>
20.<td>
21.<html:submit value="Add" onclick="submitForm()" />
22.</td>
23.</tr>
24.<tr>
25.<td>
26.<html:submit property="method" value="update" />
27.</td>
28.</tr>
29.<tr>
30.<td>
31.<html:submit property="method" >delete</html:submit>
32.</td>

33.</tr>
34.</table>
35.</html:form>
36.</body>
37.</html>
Now consider the update and the delete button. The request parameter name
specified in the action handler is "method". So this should be specified as the
property name for the submit button. The name of the method to be invoked
and the value of the button should be the same. So when the button is
clicked the corresponding method in the UserAction will be called. The
delete button shows an alternate way to specify the value of the button.
Here the main constraint is the method name and the button name should be
same. So we can't have an update button like this "Update". Inorder to avoid
this you can call a javascript function on click of the button. Specify the
action and submit the form from javascript. In this way we can have a
different button name and method name. On click of the Add button the
action value is set to "UserAction.do?method=add" and the form is submitted
from javascript.
On executing the sample example the following page is displayed to the user.

After clicking the add button the following page is displayed.


Struts tutorial

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