Spring MVC Hello World Example(转)
In Spring MVC web application, it consist of 3 standard MVC (Model, Views, Controllers) components :
- Models – Domain objects that are processed by service layer (business logic) or persistent layer (database operation).
- Views – Usually JSP page written with Java Standard Tag Library (JSTL).
- Controllers – Interact with service layer for business processing and return a Model.
See following figures 1.1, 1.2 to demonstrate how Spring MVC web application handle a web request.
Figure 1.1 – Image copied from Spring MVC reference with slightly modification.
Figure 1.2 – P.S Image copied from book : Spring Recipes
Spring MVC Tutorial
In this tutorial, you will create a simple Spring MVC hello world web application in order to understand the basic concepts and configurations of this framework.
Technologies used in this tutorial.
- Spring 2.5.6
- JDK 1.6
- Eclipse 3.6
- Maven 3
1. Directory Structure
Final directory structure of this tutorial.
2. Dependency library
Spring MVC required two core dependency libraries, spring-version.jar and spring-mvc-version.jar. If you are using JSP page with jstl, include the jstl.jar and standard.jar as well.
File : pom.xml
<!-- Spring framework --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring</artifactId> <version>2.5.6</version> </dependency> <!-- Spring MVC framework --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>2.5.6</version> </dependency> <!-- JSTL --> <dependency> <groupId>javax.servlet</groupId> <artifactId>jstl</artifactId> <version>1.1.2</version> </dependency> <dependency> <groupId>taglibs</groupId> <artifactId>standard</artifactId> <version>1.1.2</version> </dependency> <!-- for compile only, your container should have this --> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>2.5</version> <scope>provided</scope> </dependency>
3. Spring Controller
Spring comes with many Controllers, normally, you just need to extend the AbstractController
, if you do not have other special requirement, and override the handleRequestInternal()
method and return a ModelAndView object.
File : HelloWorldController.java
package com.mkyong.common.controller;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;
public class HelloWorldController extends AbstractController{
@Override
protected ModelAndView handleRequestInternal(HttpServletRequest request,
HttpServletResponse response) throws Exception {
ModelAndView model = new ModelAndView("HelloWorldPage");
model.addObject("msg", "hello world");
return model;
}
}
- ModelAndView(“HelloWorldPage”) – The “HelloWorldPage” will pass to Spring’s viewResolver later, to indentify which view should return back to the user. (see step 6)
- model.addObject(“msg”, “hello world”) – Add a “hello world” string into a model named “msg”, later you can use JSP EL ${msg} to display the “hello world” string.
4. View (JSP page)
In this case, “view” is a jSP page, you can display the value “hello world” that is store in the model “msg” via expression language (EL) ${msg}.
File : HelloWorldPage.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<body>
<h1>Spring MVC Hello World Example</h1>
<h2>${msg}</h2>
</body>
</html>
5. Spring Configuration
In web.xml
, declared a DispatcherServlet servlet, named “mvc-dispatcher“, and act as the front-controller to handle all the entire web request which end with “htm” extension.
File : web.xml
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>Spring Web MVC Application</display-name> <servlet> <servlet-name>mvc-dispatcher</servlet-name> <servlet-class> org.springframework.web.servlet.DispatcherServlet </servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>mvc-dispatcher</servlet-name> <url-pattern>*.htm</url-pattern> </servlet-mapping> </web-app>
Alternatively, you can explicitly specify the Spring configuration file in the “contextConfigLocation” servlet parameter, to ask Spring to load your configurations besides the default “mvc-dispatcher-servlet.xml“.
File : web.xml
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>Spring Web MVC Application</display-name> <servlet> <servlet-name>mvc-dispatcher</servlet-name> <servlet-class> org.springframework.web.servlet.DispatcherServlet </servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>mvc-dispatcher</servlet-name> <url-pattern>*.htm</url-pattern> </servlet-mapping> <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/SpringMVCBeans.xml</param-value> </context-param> <listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener> </web-app>
6. Spring Beans Configuration
Declared the Spring Controller and viewResolver.
File : mvc-dispatcher-servlet.xml
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> <bean name="/welcome.htm" class="com.mkyong.common.controller.HelloWorldController" /> <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver" > <property name="prefix"> <value>/WEB-INF/pages/</value> </property> <property name="suffix"> <value>.jsp</value> </property> </bean> </beans>
- Controller – Declared a bean name “/welcome.htm” and map it to HelloWorldController class. It means, if an URL with “/welcome.htm” pattern is requested, it will send to the HelloWorldController controller to handle the request.
- viewResolver – Define how Spring will looking for the view template. In this case, the controller “HelloWorldController” will return a ModelAndView object named “HelloWorldPage”, and the viewResolver will find the file with following mechanism : “prefix + ModelAndView name + suffix“, which is “/WEB-INF/pages/HelloWorldPage.jsp“.
7. Demo
Run it and access via URL : http://localhost:8080/SpringMVC/welcome.htm , the “SpringMVC” is your project context name.
How it works?
- http://localhost:8080/SpringMVC/welcome.htm is requested.
- URL is end with “.htm” extension, so it will redirect to “DispatcherServlet” and send request to the default BeanNameUrlHandlerMapping.
- BeanNameUrlHandlerMapping return HelloWorldController to the DispatcherServlet.
- DispatcherServlet forward request to the HelloWorldController.
- HelloWorldController process it and return a ModelAndView object named “HelloWorldPage”.
- DispatcherServlet received the ModelAndView and call the viewResolver to process it.
- viewResolver return the “/WEB-INF/pages/HelloWorldPage.jsp” back to the DispatcherServlet.
- DispatcherServlet return the “HelloWorldPage.jsp” back to user.