Tuesday, October 29, 2013

Spring 3 MVC: Create Hello World Application In Spring 3.0 MVC

Welcome to the Part 2 of Spring 3.0 MVC Series. In previous article we went through the Introduction of Spring MVC 3.0 framework, its request processing lifecycle and architecture diagram. In this article, let us create a simple Hello World application in Spring MVC 3.0.
For creating the hello world demo application, we will use Eclipse IDE.

Things We Need

Before we starts with our first Hello World Spring MVC Example, we will need few tools.
  1. JDK 1.5 above (download)
  2. Tomcat 5.x above or any other container (Glassfish, JBoss, Websphere, Weblogic etc) (download)
  3. Eclipse 3.2.x above (download)
  4. Spring 3.0 MVC JAR files:(download). Following are the list of JAR files required for this application.
    • commons-logging-1.0.4.jar
    • jstl-1.2.jar
    • org.springframework.asm-3.0.1.RELEASE-A.jar
    • org.springframework.beans-3.0.1.RELEASE-A.jar
    • org.springframework.context-3.0.1.RELEASE-A.jar
    • org.springframework.core-3.0.1.RELEASE-A.jar
    • org.springframework.expression-3.0.1.RELEASE-A.jar
    • org.springframework.web.servlet-3.0.1.RELEASE-A.jar
    • org.springframework.web-3.0.1.RELEASE-A.jar
Note that depending on the current version of Spring MVC, the version number of above jar files may change.

Our Goal

Our goal is to create a basic Spring MVC application using latest 3.0 version. There will be an index page which will display a link “Say Hello” to user. On clicking this link, user will be redirected to another page hello which will display a message “Hello World, Spring 3.0!”.
spring-mvc-hello-world-screen

Getting Started

Let us start with our first Spring 3.0 MVC based application.
Open Eclipse and goto File -> New -> Project and select Dynamic Web Project in the New Project wizard screen.
Dynamic Web Project in Eclipse
After selecting Dynamic Web Project, press Next.
eclipse-dynamic-web-project
Write the name of the project. For example Spring3MVC. Once this is done, select the target runtime environment (e.g. Apache Tomcat v6.0). This is to run the project inside Eclipse environment. After this press Finish.
Once the project is created, you can see its structure in Project Explorer.
spring-mvc-3-eclipse-project
Now copy all the required JAR files in WebContent > WEB-INF > lib folder. Create this folder if it does not exists.
spring-3-mvc-jar-files

The Spring Controller Class

We will need a spring mvc controller class that will process the request and display a “Hello World” message. For this we will create a package net.viralpatel.spring3.controller in the source folder. This package will contain the Controller file.
spring-3-package
Create a class called HelloWorldController in net.viralpatel.spring3.controller package and copy following content into it.
File: net.viralpatel.spring3.controller.HelloWorldController
package net.viralpatel.spring3.controller;
 
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
 
@Controller
public class HelloWorldController {
 
    @RequestMapping("/hello")
    public ModelAndView helloWorld() {
 
        String message = "Hello World, Spring 3.0!";
        return new ModelAndView("hello", "message", message);
    }
}
Note that we have annotated the HelloWorldController class with @Controller and@RequestMapping("/hello") on line 7 and 10. When Spring scans our package, it will recognize this bean as being a Controller bean for processing requests. The @RequestMapping annotation tells Spring that this Controller should process all requests beginning with /hello in the URL path. That includes/hello/* and /hello.html.
The helloWorld() method returns ModelAndView object. The ModelAndView object tries to resolve to a view named “hello” and the data model is being passed back to the browser so we can access the data within the JSP. The logical view name will resolve to "/WEB-INF/jsp/hello.jsp". We will discuss this shortly how the logical name “hello” which is return in ModelAndView object is mapped to path /WEB-INF/jsp/hello.jsp.
The ModelAndView object also contains a message with key “message” and value “Hello World, Spring 3.0!”. This is the data that we are passing to our view. Normally this will be a value object in form of java bean that will contain the data to be displayed on our view. Here we are simply passing a string.

The View: Create JSP

To display the hello world message we will create a JSP. Note that this JSP is created in folder /WEB-INF/jsp. Create hello.jsp under WEB-INF/jsp directory and copy following content into it.
File: WEB-INF/jsp/hello.jsp
<html>
<head>
    <title>Spring 3.0 MVC Series: Hello World - ViralPatel.net</title>
</head>
<body>
    ${message}
</body>
</html>
The above JSP simply display a message using expression ${message}. Note that the name “message” is the one which we have set in ModelAndView object with the message string.
Also we will need an index.jsp file which will be the entry point of our application. Create a file index.jsp under WebContent folder in your project and copy following content into it.
File: WebContent/index.jsp
<html>
<head>
    <title>Spring 3.0 MVC Series: Index - ViralPatel.net</title>
</head>
<body>
    <a href="hello.html">Say Hello</a>
</body>
</html>

Mapping Spring MVC in WEB.xml

As discussed in the previous article (Introduction to Spring 3.0 MVC), the entry point of Spring MVC application will be the Servlet define in deployment descriptor (web.xml). Hence we will define an entry oforg.springframework.web.servlet.DispatcherServlet class in web.xml.
Open web.xml file which is under WEB-INF folder and copy paste following code.
File: WEB-INF/web.xml
xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:web="http://java.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">
    <display-name>Spring3MVC</display-name>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
 
    <servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>spring</servlet-name>
        <url-pattern>*.html</url-pattern>
    </servlet-mapping>
</web-app>
The above code in web.xml will map DispatcherServlet with url pattern *.html. Also note that we have define index.jsp as welcome file.
One thing to note here is the name of servlet in tag in web.xml. Once the DispatcherServlet is initialized, it will looks for a file name [servlet-name]-servlet.xml in WEB-INF folder of web application. In this example, the framework will look for file called spring-servlet.xml.

Spring configuration file

Create a file spring-servlet.xml in WEB-INF folder and copy following content into it.
File: WEB-INF/spring-servlet.xml
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"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
 
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
 
 
http://www.springframework.org/schema/context
 
 
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
 
    <context:component-scan
        base-package="net.viralpatel.spring3.controller" />
         
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>
</beans>
In the above xml configuration file, we have defined a tag . This will allow Spring to load all the components from package net.viralpatel.spring3.controller and all its child packages. This will load our HelloWorldController class. Also we have defined a bean viewResolver. This bean will resolve the view and add prefix string /WEB-INF/jsp/ and suffix .jsp to the view in ModelAndView. Note that in our HelloWorldController class, we have return a ModelAndView object with view name “hello”. This will be resolved to path /WEB-INF/jsp/hello.jsp.

That’s All Folks

You may want to run the application now and see the result. I assume you have already configured Tomcat in eclipse. All you need to do:
Open Server view from Windows > Show View > Server. Right click in this view and select New > Server and add your server details.
To run the project, right click on Project name from Project Explorer and select Run as > Run on Server (Shortcut: Alt+Shift+X, R)
spring-mvc-hello-world-screen

Download Source Code

Moving On

In this tutorial we created a small Hello World application using Spring 3.0 MVC framework. Also we learned about the spring configuration and different annotations like @Controller and@RequestMapping. In next article we will see how easy it is to handle form data using Spring 3.0 MVC.

Related Posts

  1. Spring 3 MVC Interceptor tutorial with example
  2. Change spring-servlet.xml Filename (Spring Web Contenxt Configuration Filename)
  3. Spring 3 MVC – Introduction to Spring 3 MVC Framework
  4. Spring 3 MVC: Handling Forms in Spring 3.0 MVC
  5. Spring 3 MVC: Themes in Spring-Tutorial with Example
  6. Spring MVC HashMap Form Integration example
  7. Spring 3 MVC: Internationalization & Localization Tutorial with Example
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