Creating a Web Application with Spring

1. Overview

The tutorial illustrates how to create a Web Application with Spring.

We’ll look into the Spring Boot solution for building the application and also see a non-Spring Boot approach.

We’ll primarily use Java configuration, but also have a look at their equivalent XML configuration.

2. Setting Up Using Spring Boot

2.1. Maven Dependency

First, we’ll need the spring-boot-starter-web dependency:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

This starter includes:

• spring-web and the spring-webmvc module that we need for our Spring web application
• a Tomcat starter so that we can run our web application directly without explicitly installing any server

2.2. Creating a Spring Boot Application

The most straightforward way to get started using Spring Boot is to create a main class and annotate it with @SpringBootApplication:

@SpringBootApplication
public class SpringBootRestApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootRestApplication.class, args);
    }
}

This single annotation is equivalent to using @Configuration, @EnableAutoConfiguration, and @ComponentScan.

By default, it will scan all the components in the same package or below.

Next, for Java-based configuration of Spring beans, we need to create a config class and annotate it with @Configuration annotation:

@Configuration
public class WebConfig {

}

This annotation is the main artifact used by the Java-based Spring configuration; it is itself meta-annotated with @Component, which makes the annotated classes standard beans and as such, also candidates for component-scanning.

The main purpose of @Configuration classes is to be sources of bean definitions for the Spring IoC Container. For a more detailed description, see the official docs.

Let’s also have a look at a solution using the core spring-webmvc library.

3. Setting Up Using spring-webmvc

3.1. Maven Dependencies

First, we need the spring-webmvc dependency:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>5.3.3</version>
</dependency>

3.2. The Java-based Web Configuration

Next, we’ll add the configuration class that has the @Configuration annotation:

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = "com.baeldung.controller")
public class WebConfig {
   
}

Here, unlike the Spring Boot solution, we’ll have to explicitly define @EnableWebMvc for setting up default Spring MVC Configurations and @ComponentScan to specify packages to scan for components.

The @EnableWebMvc annotation provides the Spring Web MVC configuration such as setting up the dispatcher servlet, enabling the @Controller and the @RequestMapping  annotations and setting up other defaults.

@ComponentScan configures the component scanning directive, specifying the packages to scan.

3.3. The Initializer Class

Next, we need to add a class that implements the WebApplicationInitializer interface:

public class AppInitializer implements WebApplicationInitializer {

    @Override
    public void onStartup(ServletContext container) throws ServletException {
        AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
        context.scan("com.baeldung");
        container.addListener(new ContextLoaderListener(context));

        ServletRegistration.Dynamic dispatcher = 
          container.addServlet("mvc", new DispatcherServlet(context));
        dispatcher.setLoadOnStartup(1);
        dispatcher.addMapping("/");   
    }
}

Here, we’re creating a Spring context using the AnnotationConfigWebApplicationContext class, which means we’re using only annotation-based configuration. Then, we’re specifying the packages to scan for components and configuration classes.

Finally, we’re defining the entry point for the web application – the DispatcherServlet.

This class can entirely replace the web.xml file from <3.0 Servlet versions.

4. XML Configuration

Let’s also have a quick look at the equivalent XML web configuration:

<context:component-scan base-package="com.baeldung.controller" />
<mvc:annotation-driven />

We can replace this XML file with the WebConfig class above.

To start the application, we can use an Initializer class that loads the XML configuration or a web.xml file. For more details on these two approaches, check out our previous article.

5. Conclusion

In this article, we looked into two popular solutions for bootstrapping a Spring web application, one using the Spring Boot web starter and other using the core spring-webmvc library.

In the next article on REST with Spring, I cover setting up MVC in the project, configuration of the HTTP status codes, payload marshalling, and content negotiation.