Understanding the ViewResolver Class in Spring MVC

What is ViewResolver class

In the context of Spring Framework, particularly in Spring MVC, a ViewResolver is an interface that helps in resolving logical view names to actual view implementations. When a controller returns a logical view name (a string), the ViewResolver is responsible for mapping that name to a specific view technology (like JSP, Thymeleaf, etc.) and returning the corresponding view object.

Key Points about ViewResolver:

1. Purpose: The main purpose of a ViewResolver is to decouple the view layer from the controller layer by allowing the controller to return logical view names instead of concrete view implementations.

2. Types of ViewResolvers: There are several implementations of the ViewResolver interface in Spring, including:

   • InternalResourceViewResolver: Resolves view names to JSP files.
   • BeanNameViewResolver: Resolves view names to Spring beans.
   • XmlViewResolver: Resolves view names based on an XML configuration.
   • ThymeleafViewResolver: Resolves view names to Thymeleaf templates.

3. Configuration: You can configure a ViewResolver in your Spring configuration file (XML or Java-based configuration). For example, in Java configuration, you might define an InternalResourceViewResolver like this:

   @Bean
   public InternalResourceViewResolver viewResolver() {
       InternalResourceViewResolver resolver = new InternalResourceViewResolver();
       resolver.setPrefix("/WEB-INF/views/");
       resolver.setSuffix(".jsp");
       return resolver;
   }
   

4. Order of Resolution: If multiple ViewResolver instances are defined, they are checked in the order of their configuration until one of them successfully resolves the view name.

5. Return Type: The resolveViewName method of the ViewResolver interface returns a View object, which is then used by the DispatcherServlet to render the response.

Example Usage:

In a typical Spring MVC application, a controller might return a view name like this:

@Controller
public class MyController {
    @GetMapping("/hello")
    public String hello() {
        return "hello"; // Logical view name
    }
}

The ViewResolver will take the logical view name "hello" and resolve it to a specific view implementation (e.g., hello.jsp if using InternalResourceViewResolver).

Conclusion:

The ViewResolver is a crucial component in the Spring MVC architecture, enabling a clean separation between the controller logic and the view rendering logic, thus promoting a more maintainable and flexible application structure.