Introduction:
- The chapter will explain the interceptor “chain” in Struts 2 with an example program.
chain Interceptor:
- As the name suggests, chain interceptor is used for chaining the actions in Struts 2.
- A sequence of action classes can be executed by chain interceptor. That is, more than one action class can be executed by the implemented chain interceptor.
- In our example, the web application gets the details like name, model no, price and the number of units to purchase of a car from user and displays the total amount to pay on the next page to the user. So the first.jsp can be coded as:
// first.jsp
<%--
Document : first
Created on : Nov 20, 2014, 12:34:17 PM
Author : Wideskills.com
--%>
<%@page contentType = "text/html" pageEncoding = "UTF-8"%>
<%@taglib prefix = "s" uri = "/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv = "Content-Type" content = "text/html; charset = UTF-8">
<title> Get your Car Application - Main Page </title>
</head>
<body>
<s:form action = "click" method = "POST">
<h1> Car details </h1>
<hr/>
<s:label value = "Enter name"/> <s:textfield name = "name"/>
<s:label value = "Enter model no."/> <s:textfield name = "id"/>
<s:label value = "Enter price"/> <s:textfield name = "price"/>
<s:label value = "Enter the number of units to purchase"/>
<s:textfield name = "units"/>
<s:submit name = "SUBMIT"/>
<s:reset name = "RESET"/>
</s:form>
</body>
</html>
- The next.jsp will gather the information from first.jsp, and will calculate the total amount to pay.
- So, next.jsp can be written as follows:
//next.jsp
<%--
Document : next
Created on : Nov 20, 2014, 12:50:20 PM
Author : Admin
--%>
<%@page contentType = "text/html" pageEncoding = "UTF-8"%>
<%@taglib prefix = "s" uri = "/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv = "Content-Type" content = "text/html; charset = UTF-8">
<title> Get your Car Application - Invoice Page </title>
</head>
<body>
<h1> Purchase Invoice of Car </h1>
<hr/>
<h4>
<s:label value = "Car Model Number : "/> <s:property value = "id"/>
</h4>
<h4>
<s:label value = "Car Name : "/> <s:property value = "name"/>
</h4>
<h4>
<s:label value = "Price of 1 unit : "/> <s:property value = "price"/>
</h4>
<h4>
<s:label value = "Total Price : "/> <s:property value = "answer"/>
</h4>
</body>
</html>
- The first.jsp will run as follows:
Figure-1
- Now, as we have to use chain interceptor (chaining of action classes), we will create two action classes here.
- Myaction_1.java – only responsible for details of Model ID and car name.
- Myaction_2.java – responsible for calculating final payable amount from the price entered and number of units of be purchased.
- So Myaciton1.java will be coded as:
// Myaction_1.java
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package action_class;
import com.opensymphony.xwork2.ActionSupport;
import java.io.*;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.io.FileUtils;
import org.apache.struts2.interceptor.ServletRequestAware;
/**
*
* @author Admin
*/
public class Myaction_1 extends ActionSupport
{
private String id;
private String name;
public String getId()
{
return id;
}
public String getName()
{
return name;
}
public void setId(String id)
{
this.id = id;
}
public void setName(String name)
{
this.name = name;
}
public String execute()
{
return SUCCESS;
}
}
- And Myaction_2.java will be as follows:
// Myaction_2.java
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package action_class;
import com.opensymphony.xwork2.ActionSupport;
/**
*
* @author Admin
*/
public class Myaction_2 extends ActionSupport
{
private int price,units,answer;
public int getUnits()
{
return units;
}
public void setUnits(int units)
{
this.units = units;
}
public int getAnswer()
{
return answer;
}
public void setAnswer(int answer)
{
this.answer = answer;
}
public int getPrice()
{
return price;
}
public void setPrice(int price)
{
this.price = price;
}
public String execute()
{
answer = units * price;
return "success";
}
}
- Now to combine our JSP’s with action class, we need to configure our struts.xml.
//struts.xml
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<package name = "default" namespace = "/" extends = "struts-default">
<action name = "click" class = "action_class.Myaction_1">
<result name = "success" type = "chain"> Myaction_2 </result>
</action>
<action name = "Myaction_2" class = "action_class.Myaction_2">
<result name = "success"> jsp/next.jsp </result>
</action>
</package>
</struts>
- The chain interceptor element is given in result element with following syntax:
<result name = “Name of result” type = “chain” > JSP page name </result>
- In our example, on click of submit button, Myaction_1.java should be executed followed by another action class (chain) – Myaction_2.java. So the action element can be written as:
<action name = "click" class = "action_class.Myaction_1">
<result name = "success" type = "chain"> Myaction_2 </result>
</action>
- And again, on the success of Myaction_2.java, next.jsp is to be displayed. That is,
<action name = "Myaction_2" class = "action_class.Myaction_2">
<result name = "success"> jsp/next.jsp </result>
</action>
- And at last, web.xml can be given as:
//web.xml
<?xml version = "1.0" encoding = "UTF-8"?>
<web-app version = "3.1" xmlns = "http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation = "http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
<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>
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file> jsp/first.jsp </welcome-file>
</welcome-file-list>
</web-app>
- So the application will run as follows:
Figure: First run of application
