Programming Tutorials

(追記) (追記ここまで)

Writing the first Struts application

By: Norman Chap in Struts Tutorials on 2007年09月22日 [フレーム]

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.xml

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 = "";
lastName = "";
}
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>