1. Introduction
In this quick tutorial, we’ll have a look at one of the warnings we may see when working with a Spring 5.x.x version, namely the one referring to the deprecated WebMvcConfigurerAdapter class.
We’ll see why this warning happens and how to handle it.
2. Why the Warning Is Present
This warning will appear if we’re using Spring version 5 (or Spring Boot 2), either when upgrading an existing application or building a new application with the old API.
Let’s briefly go through the history behind it.
In earlier versions of Spring, up to and including version 4, if we wanted to configure a web application, we could make use of the WebMvcConfigurerAdapter class:
@Configuration
public WebConfig extends WebMvcConfigurerAdapter {
// ...
}
This is an abstract class that implements the WebMvcConfigurer interface and contains empty implementations for all the methods inherited.
By subclassing it, we can override its methods, which provide hooks into various MVC configuration elements such as view resolvers, interceptors and more.
However, Java 8 added the concept of default methods in interfaces. Naturally, the Spring team updated the framework to make full use of the new Java language features.
3. Solution
As mentioned, the WebMvcConfigurer interface, starting with Spring 5, contains default implementations for all its methods. As a result, the abstract adapter class was marked as deprecated.
Let’s see how we can start using the interface directly and get rid of the warning:
@Configuration
public WebConfig implements WebMvcConfigurer {
// ...
}
And that’s all! The change should be fairly easy to make.
If there are any super() calls to overridden methods, we should remove those as well. Otherwise, we can override any of the configuration callbacks as usual.
While removing the warning is not mandatory, it’s recommended to do so, as the new API is more convenient, and the deprecated class may be removed in future versions.
4. Conclusion
In this short article, we saw how to fix the warning referring to the deprecation of the WebMvcConfigurerAdapter class.
