An introduction and web application example
Typically, each team work on a single level of a classic three-tiers architecture:
- Presentation layer
- Business Logic layer
- Physical layer
I tried out almost all the most published solutions to take this task and I found this one, that I’m going to explain in this article, the more efficient and easy to implement.
Wait wait!! ..marginal note: I switched to MyEclipse IDE since two months, I never loved Eclipse as IDE, too many configuration settings, not intuitive user interaction, very mnemonic use required, everywhere you click-right, a big menu will be open.. But MyEclipse rocks! Explosed deployment and plugins (dependency) management are features useful enough to motivate my emphasis on this tool.
On other IDEs, I suppose there are other ways to add these supports to main project, the result, however, will be exactly this:
Fig. 1 Libraries included
and at the end of the file, first of tag closing, write:
This snippet of code sets a listener to use Spring as Struts action manager.
<listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener>
so web.xml file will look like this:
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <filter> <filter-name>struts2</filter-name> <filter-class> org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter </filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener> </web-app>
Tutorials on these missing features will be submitted in the near future (I am writing several articles on Hibernate and JQuery).
Our application uses a Struts Action to call an interface of a concrete implementation of a service and then, through action, it whows results to a JSP.
Here the UML code:
Struts Action code:
package it.nickg.webapp.web.actions;
import it.nickg.webapp.services.HelloService;
import java.util.List;
import com.opensymphony.xwork2.ActionSupport;
public class HelloAction extends ActionSupport {
private HelloService helloService;
private List words;
public List getWords() {
return words;
}
public void setWords(List words) {
this.words = words;
}
public HelloService getHelloService() {
return helloService;
}
public void setHelloService(HelloService helloService) {
this.helloService = helloService;
}
public String execute() throws Exception {
words = helloService.getWords();
return SUCCESS;
}
}
Struts2 apply dependency injection through setters, so every variable that you need to use in jsp, must have a setter (and I add getter too).
HelloService Interface code:
package it.nickg.webapp.services;
import java.util.List;
public interface HelloService {
public abstract List getWords();
// mandatory setter method for Spring's dependency injection
public abstract void setWords(List words);
}
HelloServiceImpl, real service implementation:
package it.nickg.webapp.services.impl;
import it.nickg.webapp.services.HelloService;
import java.io.Serializable;
import java.util.List;
public class HelloServiceImpl implements Serializable, HelloService {
private List words;
public List getWords() {
return words;
}
public void setWords(List words) {
this.words = words;
}
}
Now edit struts.xml file to map the action created:
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd"> <struts> <package name="default" extends="struts-default"> <action name="hello" class="helloAction"> <result type="success">/result.jsp</result> </action> </package> </struts>
<h3><span style=”font-size: small;”><strong>Crucial note: what allows to estabilish the link between Struts and Spring is here, <em>class </em>parameter of action must be set as <em>id </em>of spring’s bean calling that action<span style=”font-size: x-small;”>.</span></strong></span></h3>
Add this code to applicationContext.xml file
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="helloService" class="it.nickg.webapp.services.impl.HelloServiceImpl"> <property name="words"> <list> <value>Hello </value> <value>World! </value> <value>This is </value> <value>a Struts - Spring </value> <value>integration example</value> </list> </property> </bean> <bean id="helloAction" class="it.nickg.webapp.web.actions.HelloAction"> <property name="helloService" ref="helloService"/> </bean> </beans>
Now we write JSPs. Let’s give to index.jsp the role to redirect to our action:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <c:redirect url="hellopage.action"/>
and write the “success.jsp” in order to display data returned from action:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; %> <%@ taglib prefix="s" uri="/struts-tags"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'success.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <h3>This is only a sample</h3> <s:iterator value="words"> <s:property/> </s:iterator> </body> </html>
When you run the application, it goes to index.jsp, redirected to hellopage.action and from here to success.jsp that displays an output like this:
In the next article, I will start from this application and I will extend it to physical layer, adding a database and an ORM implementation.
Nick's place 