Discover the Top 5 New Features in Spring Boot 4 Preview

When creating a new Spring Boot project, the preview version Spring Boot 4.0.0 is already available.

Spring Boot 4 is built on the brand‑new Spring Framework 7.0.0.

Here are the most important changes in the new version.

1. Elegant version control

The new version introduces graceful API versioning support, allowing developers to specify a version parameter in the @RequestMapping annotation.

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/api")
public class VersionedController {

    @RequestMapping(value = "/user", version = "1")
    public String getUserV1() {
        // version 1 implementation
        System.out.println("Version 1");
        return "Version 1";
    }

    @RequestMapping(value = "/user", version = "2")
    public String getUserV2() {
        // version 2 implementation
        System.out.println("Version 2");
        return "Version 2";
    }
}

Execution result:

2. Convenient bean injection

The new version adds a BeanRegistrar contract that enables flexible registration of multiple beans at once.

import org.springframework.beans.factory.BeanRegistrar;
import org.springframework.beans.factory.BeanRegistry;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.env.Environment;

@Configuration
@Import(MyBeansRegistrar.class)
public class MyConfiguration {
}

class MyBeansRegistrar implements BeanRegistrar {
    @Override
    public void register(BeanRegistry registry, Environment env) {
        registry.registerBean("user", User.class);
        if (env.matchesProfiles("dev")) {
            registry.registerBean(Order.class, spec -> spec.supplier(context -> new Order("order_001")));
        }
    }
}

class User {
    private String name;
}

class Order {
    public Order(String name) { this.name = name; }
    private String name;
}

A unit test proves the registered beans work correctly:

3. Null‑safety improvements

The new version adopts JSpecify annotations to declare API nullability, using @Nullable for optional values and @NonNull for required ones, with IDE warnings.

import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

public class Person {
    private String name;

    public void setName(@NonNull String name) {
        this.name = name;
    }

    @Nullable
    public String getName() {
        return this.name;
    }
}

IDE shows the warning as shown:

Different IDE versions display the warning differently; the author used IntelliJ IDEA 2024.

4. Easy HTTP proxy creation

The new @ImportHttpServices annotation makes creating HTTP service proxies simpler, allowing you to declare, detect, and configure whole groups of HTTP services.

@Configuration(proxyBeanMethods = false)
@ImportHttpServices(group = "weather", types = {FreeWeather.class, CommercialWeather.class})
public class HttpServicesConfiguration extends AbstractHttpServiceRegistrar {
    @Bean
    public RestClientHttpServiceGroupConfigurer groupConfigurer() {
        return groups -> groups.filterByName("weather", "user")
            .configureClient((group, builder) -> builder.defaultHeader("User-Agent", "My-Application"));
    }
}

5. Other seven changes

Additional upgrades include:

SPEL expression upgrade : support for null‑safe and Elvis operators, e.g., @Value("#{systemProperties['pop3.port'] ?: 25}").

GraalVM native application support : compile applications to native images via Spring AOT, drastically reducing startup time.

Jackson 3.x support : drop support for Jackson 2.x and upgrade to Jackson 3.x.

Servlet and WebSocket version upgrade : use Servlet 6.1 and WebSocket 2.2, requiring Tomcat 11+ or Jetty 12.1+.

HttpHeaders optimization : new firstValue method and easier iteration of headers.

Feature removals : deprecated Spring MVC XML namespace, JUnit 4 support in TestContext, Jackson 2.x, and Spring JCL.

Higher minimum environment requirements : Jakarta EE 11, Kotlin 2.x, JSONassert 2.0, GraalVM 23.

For more upgrade details, see the official release notes: https://github.com/spring-projects/spring-framework/wiki/Spring-Framework-7.0-Release-Notes

Conclusion

Framework and tool changes bring more convenient and friendly usage for developers, making it a win for programmers to learn, use, and experiment.