Gradle – Spring 4 MVC Hello World Example – Annotation

In this tutorial, we will take the previous Gradle + Spring MVC XML example, rewrite it to support @JavaConfig annotation configuration, no more XML files.

P.S This example will works in Servlet 3.0+ container only, like Tomcat 7 or Jetty 9.

Technologies used :

• Gradle 2.0
• Spring 4.1.6.RELEASE
• Tomcat 7 or Jetty 9
• Eclipse 4.4
• JDK 1.7
• Logback 1.1.3
• Boostrap 3

1. Project Structure

Download the project source code and review the project folder structure :

P.S No more XML files like web.xml or Spring XML configuration files.

2. Gradle

2.1 Review the build.gradle file, this should be self-explanatory.

build.gradle

apply plugin: 'java'
apply plugin: 'war'
apply plugin: 'eclipse-wtp'
//apply plugin: 'jetty' //too old, Jetty 6, use gretty plugin
apply plugin: 'org.akhikhl.gretty'

// JDK 7
sourceCompatibility = 1.7
targetCompatibility = 1.7

repositories {
    mavenLocal()
    mavenCentral()
}

dependencies {
    compile 'ch.qos.logback:logback-classic:1.1.3'
    compile 'org.springframework:spring-webmvc:4.1.6.RELEASE'
    compile 'javax.servlet:jstl:1.2'
	
    //include in compile only, exclude in the war
    providedCompile 'javax.servlet:servlet-api:2.5'
}

//Gretty Embedded Jetty
buildscript {
  repositories {
    jcenter()
  }

  dependencies {
    classpath 'org.akhikhl.gretty:gretty:+'
  }
}

// Don't use Jetty8, even it's a servlet 3.0+ container, 
// but not support non-jar WebApplicationInitializer scanning.
// It will cause "No Spring WebApplicationInitializer types detected on classpath"
gretty {
  port = 8080
  contextPath = 'spring4'
  servletContainer = 'jetty9' //tomcat7 or tomcat8
}

//For Eclipse IDE only
eclipse {

  wtp {
    component {
      
      //define context path, default to project folder name
      contextPath = 'spring4'
      
    }
    
  }
}

2.2 Make this project supports Eclipse IDE. Now, you can import the project into Eclipse IDE.

your-project$ gradle eclipse

3. Spring @Configuration

Spring @Configuration and its XML equivalent.

3.1 Spring annotation configuration to scan the service classes.

SpringRootConfig.java

package com.mkyong.helloworld.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan({ "com.mkyong.helloworld.service" })
public class SpringRootConfig {
}

XML equivalent.

spring-core-config.xml

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context.xsd ">
 
	<context:component-scan base-package="com.mkyong.helloworld.service" />

</beans>

3.2 Extends abstract class WebMvcConfigurerAdapter.

SpringWebConfig.java

package com.mkyong.helloworld.config;
 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import org.springframework.web.servlet.view.JstlView;
 
@EnableWebMvc //<mvc:annotation-driven />
@Configuration
@ComponentScan({ "com.mkyong.helloworld.web" })
public class SpringWebConfig extends WebMvcConfigurerAdapter {
 
	@Override
	public void addResourceHandlers(ResourceHandlerRegistry registry) {
		registry.addResourceHandler("/resources/**")
                        .addResourceLocations("/resources/");
	}
	
	@Bean
	public InternalResourceViewResolver viewResolver() {
		InternalResourceViewResolver viewResolver 
                         = new InternalResourceViewResolver();
		viewResolver.setViewClass(JstlView.class);
		viewResolver.setPrefix("/WEB-INF/views/jsp/");
		viewResolver.setSuffix(".jsp");
		return viewResolver;
	}
 
}

XML equivalent.

spring-web-config.xml

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc 
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context.xsd ">
 
	<context:component-scan base-package="com.mkyong.helloworld.web" />
 
	<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
		<property name="prefix" value="/WEB-INF/views/jsp/" />
		<property name="suffix" value=".jsp" />
	</bean>
 
	<mvc:resources mapping="/resources/**" location="/resources/" />
	 
	<mvc:annotation-driven />
 
</beans>

4. Servlet 3.0+ Container

Create a ServletInitializer class, Servlet 3.0+ container will pick up this class and run it automatically. This is the replacement class for web.xml

package com.mkyong.helloworld.servlet3;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

import com.mkyong.helloworld.config.SpringRootConfig;
import com.mkyong.helloworld.config.SpringWebConfig;

public class MyWebInitializer extends
		AbstractAnnotationConfigDispatcherServletInitializer {

	@Override
	protected Class<?>[] getRootConfigClasses() {
		return new Class[] { SpringRootConfig.class };
	}

	@Override
	protected Class<?>[] getServletConfigClasses() {
		return new Class[] { SpringWebConfig.class };
	}

	@Override
	protected String[] getServletMappings() {
		return new String[] { "/" };
	}

}

XML equivalent.

web.xml

<web-app 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"
	version="2.5">

	<display-name>Gradle + Spring MVC Hello World</display-name>
	<description>Spring MVC web application</description>

	<!-- For web context -->
	<servlet>
		<servlet-name>hello-dispatcher</servlet-name>
		<servlet-class>
			org.springframework.web.servlet.DispatcherServlet
		</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>/WEB-INF/spring-mvc-config.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>

	<servlet-mapping>
		<servlet-name>hello-dispatcher</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>

	<!-- For root context -->
	<listener>
		<listener-class>
			org.springframework.web.context.ContextLoaderListener
		</listener-class>
	</listener>

	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>/WEB-INF/spring-core-config.xml</param-value>
	</context-param>

</web-app>

Note
There is no change in the Spring controller, logback and JSP files, so, the source code will not repeat here, please refer to the previous Gradle + Spring MVC XML example for complete source code.

5. Demo

5.1 To run this project. Issues gradle jettyRun to start the embedded Jetty container.

Terminal

your-project$ gradle jettyRun

21:56:34 INFO  Jetty 9.2.10.v20150310 started and listening on port 8080
21:56:34 INFO  spring4 runs at:
21:56:34 INFO    http://localhost:8080/spring4
Press any key to stop the server.
> Building 87% > :jettyRun

5.2 http://localhost:8080/spring4/

5.3 http://localhost:8080/spring4/hello/mkyong.com