Writing the first Struts application

By: Norman Chap

Let's start with developing your first Struts application. Here are the steps involved in creating the Struts application.


  
    Add relevant entries into the web.xml

      

      a. Add ActionServlet Configuration with initialization
parameters

b. Add ActionServlet Mapping

c. Add relevant taglib declaration

    
    Start with a blank template for the struts-config.xml. In the
struts-config.xml, add the following


a. Declare the RequestProcessor

b. Create a properties file and declare it as Message Resource
Bundle

c. Declare the Message Resource Bundle

d. Declare the Form-bean

e. Declare the ActionMapping for the Form-bean

f. Add the forwards in the ActionMapping

    
    Create the Form-bean class
    Create the JSP with Struts tags
    Create the Action class
    For every <bean:message> tag in the JSP, add key value
pairs to the Message Resource Bundle (properties file) created in Step 2b
    Add Validation in the Form-bean
    Define the error messages in the Message Resource Bundle
    Create the rest of the JSPs.

Next, you will find the steps to build the Struts application. You will find more explanation & rationale for the steps in the book Struts Survival Guide.

1. Add relevant entries into the web.xm


  web.xml for the Struts Application
  <?xml version="1.0"
encoding="ISO-8859-1"?>

<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application
2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>

<display-name>Hello World Struts
Application</display-name>

<servlet>

<servlet-name>action</servlet-name>

<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>

<init-param>

<param-name>config</param-name>

<param-value>/WEB-INF/struts-config.xml</param-value>

</init-param>

<init-param>

<param-name>debug</param-name>

<param-value>3</param-value>

</init-param>

<init-param>

<param-name>detail</param-name>

<param-value>3</param-value>

</init-param>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>action</servlet-name>

<url-pattern>*.do</url-pattern>

</servlet-mapping>

<welcome-file-list>

<welcome-file>index.jsp</welcome-file>

</welcome-file-list>

<taglib>

<taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>

<taglib-location>/WEB-INF/struts-html.tld</taglib-location>

</taglib>

<taglib>

<taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>

<taglib-location>/WEB-INF/struts-bean.tld</taglib-location>

</taglib>

</web-app>

2) Create the struts-config.xml


  struts-config.xml for the Struts Application
  <?xml version="1.0" encoding="ISO-8859-1"
?>

<!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration
1.1//EN" "http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd">

<struts-config>

<form-beans>


<form-bean name="CustomerForm" type="struts.example.CustomerForm"/>


</form-beans>

<global-forwards>


<forward name="mainpage" path="index.jsp"
/>


</global-forwards>

<action-mappings>


<action path="/submitCustomerForm"

type="struts.example.CustomerAction"

name="CustomerForm"

scope="request"

validate="true"

input="CustomerForm.jsp">

<forward name="success" path="Success.jsp"
/>

</action>


</action-mappings>


<controller processorClass="org.apache.struts.action.RequestProcessor"/>

<message-resources parameter="struts.example.MessageResources"/>


</struts-config>

3) Create the ActionForm


  CustomerForm
  public class CustomerForm extends ActionForm {

private String firstName;

private String lastName;

public CustomerForm() {

firstName = â€œâ€;

lastName = â€œâ€;

}

public String getFirstName() {

return firstName;

}

public void setFirstName(String s) {

this.firstName = s;

}

public String getLastName() {

return lastName;

}

public void setLastName(String s) {

this.lastName = s;

}

}

4) Create the CustomerForm JSP using Struts Tags


  CustomerForm.jsp
  <%@ page contentType="text/html;charset=UTF-8"
language="java" %>

<%@ taglib uri="/WEB-INF/struts-html.tld"
prefix="html" %>

<%@ taglib uri="/WEB-INF/struts-bean.tld"
prefix="bean" %>

<html:html xhtml="true">

<head>

<title><bean:message
key="exercise01.formpage.title"/></title>

<html:base/>

</head>

<body background="images/blueAndWhiteBackground.gif">

<h2><bean:message
key="exercise01.formpage.title"/></h2>

<html:errors/>

<html:form action="/submitCustomerForm">

<bean:message key="prompt.customer.firstname"/>:

<html:text property="firstName" size="16"
maxlength="16"/>

<BR>

<bean:message key="prompt.customer.lastname"/>:

<html:text property="lastName" size="16"
maxlength="16"/>

<BR>

<html:submit property="step">

<bean:message key="button.save"/>

</html:submit>

&nbsp;

<html:cancel>

<bean:message key="button.cancel"/>

</html:cancel>

</html:form>

</body>

</html:html>

5) Create the Action class


  CustomerAction class
  public class CustomerAction extends Action

{

public ActionForward execute(ActionMapping mapping, ActionForm
form,

HttpServletRequest request, HttpServletResponse response) throws
Exception

{

ActionForward nextPage = null;

if (isCancelled(request)) {

System.out.println("Cancel Operation Performed");

return mapping.findForward("mainpage");

}

CustomerForm custForm = (CustomerForm) form;

if ("Save".equals(custForm.getStep()))

{

String firstName = custForm.getFirstName();

String lastName = custForm.getLastName();

System.out.println("Customer First name is " +
firstName);

System.out.println("Customer Last name is " + lastName);

nextPage = mapping.findForward("success");

}

return nextPage;

}

}

6) Add properties to MessageResources.properties


  Message Resource Bundle
  ########################################

# Exercise01 index page strings

########################################

exercise01.indexpage.title=Welcome to Exercise01


########################################

# Exercise01 CustomerForm strings

########################################

exercise01.formpage.title=Please enter your details

prompt.customer.firstname=First Name

prompt.customer.lastname=Last Name

button.save=Save

button.cancel=Cancel

7) Add validation to the Form bean


  validate() method for CustomerForm
  public ActionErrors validate(ActionMapping mapping,
HttpServletRequest request) {

ActionErrors errors = new ActionErrors();

// Firstname cannot be empty

if (firstName == null || firstName.trim().equals(""))
{

errors.add("firstName", new
ActionError("error.cust.firstname.empty"));

}

// Lastname cannot be empty

if (lastName == null || lastName.trim().equals("")) {

errors.add("lastName", new
ActionError("error.cust.lastname.empty"));

}

return errors;

}

8) Add ActionError keys to the Message Resources


  ActionError keys to Message Resources
  ########################################

# Common

########################################

errors.header=<h3><font
color="red">Validation Error</font></h3>You must

correct the following error(s) before proceeding:<ul>

errors.footer=</ul><hr>

errors.prefix=<li>

errors.suffix=</li>


########################################

# Exercise01 CustomerForm ActionErrors

########################################

error.cust.firstname.empty=First Name is Required

error.cust.lastname.empty=Last Name is Required

9) Create the rest of the JSPs - index.jsp and Success.jsp. Notice that index.jsp uses the regular html:link tag that just forwards to another JSP. The Success.jsp uses the MVC compliant action mapping as the link. Define entries in MessageResource.properties for each of the bean:message keys in the JSPs.


  index.jsp
  <%@ page contentType="text/html;charset=UTF-8"
language="java" %>

<%@ taglib uri="/WEB-INF/struts-html.tld"
prefix="html" %>

<%@ taglib uri="/WEB-INF/struts-bean.tld"
prefix="bean" %>

<html:html xhtml="true">

<head>

<title><bean:message
key="exercise01.indexpage.title"/></title>

<html:base/>

</head>

<body background="images/blueAndWhiteBackground.gif">

<div align="center">

<html:link page="/CustomerForm.jsp">Go to
Customer Form</html:link>

</div>

</body>

</html:html>

Notice the usage of bean:write tags in Success.jsp. They let you access certain beans in appropriate scope and write their properties to the Servlet/JSP OutputStream


  Success.jsp
  <%@ page contentType="text/html;charset=UTF-8"
language="java" %>

<%@ taglib uri="/WEB-INF/struts-html.tld"
prefix="html" %>

<%@ taglib uri="/WEB-INF/struts-bean.tld"
prefix="bean" %>

<html:html xhtml="true">

<head>

<title><bean:message
key="exercise01.successpage.title"/></title>

<html:base/>

</head>

<body background="images/blueAndWhiteBackground.gif">

<h2><bean:message
key="exercise01.successpage.title" />

<bean:write name="CustomerForm" property="firstName"
/>

<bean:write name="CustomerForm" property="lastName"
/>

</h2>

<h3><bean:message
key="exercise01.successpage.message" /></h3>

<html:img src="images/beerchug.gif"/>

<html:link page="/showCustomerForm.do">Go
Back</html:link>

</body>

</html:html>