In this tutorial, we will show you a Spring MVC hello world web application.
Technologies used :
- Spring 2.5.6
- JDK 1.6
- Eclipse 3.6
- Maven 3
1. MVC Basic
In Spring MVC web application, it consists of 3 standard MVC (Model, Views, Controller) components :
- Models – Domain objects that are processed by the service layer (business logic) or persistent layer (database operation).
- Views – Display data, normally it’s a JSP page written with the Java Standard Tag Library (JSTL).
- Controllers – URL mapping and interact with service layer for business processing and return a Model.
The following figures demonstrates how the Spring MVC web application handles a web request.
spring-mvc-concepts.jpg spring-mvc-concepts-2.jpg
Note
In Spring MVC , the core dispatcher component is theDispatcherServlet
, which act as the front-controller (design pattern). Every web request has to go through thisDispatcherServlet
, and theDispatcherServlet
will dispatch the web request to suitable handlers.
2. Directory Structure
A standard Maven project directory structure.
spring2-mvc-hello-world.png
3. Maven
Declares the spring-webmvc dependency, Maven will help you manage the transitive dependencies automatically (download other dependencies that are required by spring-webmvc, like spring-context or spring-beans).
If you are using the JSP page with JSTL technology, include the jstl dependency also.
pom.xml
<?xml version="1.0"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mkyong.common</groupId>
<artifactId>spring2-mvc-xml-hello-world</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>Spring 2 MVC</name>
<properties>
<jdk.version>1.6</jdk.version>
<spring.version>2.5.6</spring.version>
<jstl.version>1.2</jstl.version>
<servletapi.version>2.5</servletapi.version>
</properties>
<dependencies>
<!-- Spring MVC framework -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<!-- JSTL -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>${jstl.version}</version>
</dependency>
<!-- for compile only, your container should have this -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>${servletapi.version}</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>${jdk.version}</source>
<target>${jdk.version}</target>
</configuration>
</plugin>
<!-- embedded jetty, good for testing -->
<plugin>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>9.2.11.v20150529</version>
<configuration>
<scanIntervalSeconds>10</scanIntervalSeconds>
<webApp>
<contextPath>/spring2</contextPath>
</webApp>
</configuration>
</plugin>
<!-- configure Eclipse workspace -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-eclipse-plugin</artifactId>
<version>2.9</version>
<configuration>
<downloadSources>true</downloadSources>
<downloadJavadocs>true</downloadJavadocs>
<wtpversion>2.0</wtpversion>
<wtpContextName>spring2</wtpContextName>
</configuration>
</plugin>
</plugins>
</build>
</project>
4. Spring Controller
Spring comes with many Controllers, normally, you just need to extend the AbstractController
, and override the handleRequestInternal()
method.
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;
}
}
4.1 ModelAndView(“HelloWorldPage”)
– To identify which view should return back to the user, in this example HelloWorldPage.jsp
will be returned.
4.2 model.addObject(“msg”, “hello world”)
– Add a “hello world
” string into a model named “msg
”, later you can use EL ${msg}
to display the “hello world
” string.
5. View (JSP page)
In this case, “view” is a JSP page, you can display the value “hello world
” that is stored in the model “msg
” via expression language (EL) ${msg}
.
HelloWorldPage.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<body>
<h1>Spring MVC Hello World Example</h1>
<h2>${msg}</h2>
</body>
</html>
6. Spring XML Configuration
6.1 Declared the Spring Controller and viewResolver.
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 toHelloWorldController
. It means, if an URL with/welcome.htm
pattern is requested, theHelloWorldController
controller will handle the request. -
viewResolver – Define how Spring will look for the view template. In this case, the controller
HelloWorldController
will return a view namedHelloWorldPage
, the viewResolver will find the file with following mechanism :prefix + view name + suffix
, which is/WEB-INF/pages/HelloWorldPage.jsp
.
Note
Actually, you don’t need to define theBeanNameUrlHandlerMapping
in theweb.xml
, by default, if no handler mapping can be found, theDispatcherServlet
will create aBeanNameUrlHandlerMapping
automatically.
6.2 In web.xml , declared a DispatcherServlet
servlet to act as the front-controller to handle all the entire web request which end with htm
extension.
web.xml
<?xml version="1.0"?>
<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>
**Note **
The mvc-dispatcher is used to define which file to load the Spring XML configurations. By default, it will look for Spring XML configuration file by joining the servlet namemvc-dispatcher
with-servlet.xml
.
In this example, Spring will look for this file –mvc-dispatcher-servlet.xml
.
7. Demo
7.1 To run this project with Maven :
$ mvn jetty:run
7.2 To run this project in Eclipse IDE, create Eclipse project settings with the following Maven command :
$ mvn eclipse:eclipse
Imports the project manually and start with the server plugin.
URL : http://localhost:8080/spring2/welcome.htm
How it works?
http://localhost:8080/spring2/welcome.htm is requested.
URL is end with “.htm
” extension, so it will redirect to “DispatcherServlet
” and send requests to the default BeanNameUrlHandlerMapping
.
BeanNameUrlHandlerMapping
return HelloWorldController
to the DispatcherServlet
.
DispatcherServlet
forward request to the HelloWorldController
.
HelloWorldController
process it and return a ModelAndView
object, with view name “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 the user.
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