Spring 7 Deep Dive: Architecture Upgrade, New HTTP Client, and Migration Guide

Positioning of Spring 7

Spring Framework 7.0 is an architecture‑level stable upgrade that serves as the core of Spring Boot 4.x, fully embraces the Java 17+ ecosystem, supports GraalVM native images, and targets enterprise Java development for the next three to five years.

Core upgrades – three dimensions

Dependency and module refactoring

JDK baseline remains JDK 17‑27; JDK 25+ is recommended to unlock new features such as the Class File API.

The spring‑jcl module is removed; Apache Commons Logging 1.3.0 is used transparently. javax.annotation packages are deprecated and must be replaced with jakarta.annotation.

Undertow container support is removed; focus shifts to Tomcat 11+ and Jetty 12+.

XML‑based configuration (vc:*) is deprecated in favor of pure Java Config.

RestTemplate is eliminated; developers should adopt WebClient or the new declarative HTTP client.

Declarative HTTP client (@HttpExchange)

Define an interface and let Spring generate the implementation, removing boilerplate request handling.

// 1. Define the client interface
public interface UserClient {
    @GetExchange("/users/{id}")
    Mono<User> getUserById(@PathVariable Long id);

    @PostExchange("/users")
    Mono<User> createUser(@RequestBody User user);
}

// 2. Configure the proxy (auto‑configured in Spring Boot 4)
@Configuration
public class HttpClientConfig {
    @Bean
    public WebClient webClient() {
        return WebClient.builder()
            .baseUrl("https://api.example.com")
            .defaultHeader("Authorization", "Bearer " + TOKEN)
            .build();
    }

    @Bean
    public UserClient userClient(WebClient webClient) {
        return HttpServiceProxyFactory
            .builderFor(WebClientAdapter.create(webClient))
            .build()
            .createClient(UserClient.class);
    }
}

// 3. Inject and use
@Service
public class UserService {
    @Autowired
    private UserClient userClient;

    public Mono<User> getUser(Long id) {
        return userClient.getUserById(id);
    }
}

Compared with Spring 6, RestTemplate requires manual request/response conversion and WebClient requires chain‑style calls; @HttpExchange provides concise syntax with reactive support.

Native API versioning support

Spring 7 offers first‑class support for multiple API versions without custom routing logic.

// Path‑based versioning
@RestController
@RequestMapping("/{version}/users")
public class UserControllerV1 {
    @GetMapping
    public Flux<User> getUsers(@PathVariable @ApiVersion("1") String version) {
        return userRepository.findAllV1();
    }
}

// Header‑based versioning
@RestController
@RequestMapping("/users")
public class UserControllerV2 {
    @GetMapping
    public Flux<User> listUsers(@RequestHeader @ApiVersion("2") String version) {
        return userRepository.findAllV2();
    }
}

// Global version‑resolution configuration
@Configuration
public class ApiVersionConfig implements WebMvcConfigurer {
    @Override
    public void configurePathMatch(PathMatchConfigurer config) {
        config.addPathPrefix("/v{version}",
            c -> c.isAnnotationPresent(ApiVersion.class));
    }
}

The framework supports path, header, and parameter versioning and can mark deprecated versions to prompt client upgrades.

Performance improvements

Startup time reduced by 30‑50 %; class‑path scanning algorithm is optimized, yielding an average context‑load time reduction of 22 % for large projects.

Method‑parameter annotation caching cuts reflection overhead in AOP scenarios.

Combined with GraalVM 24+, native image build speed improves by 40 %.

WebFlux throughput increases by roughly 25 %: event‑loop optimization, Java 21+ virtual‑thread support, and benchmark results showing Spring 6 at ~8,500 req/s versus Spring 7 at ~10,600 req/s.

Retry mechanism is moved into spring‑core, replacing the separate Spring Retry project.

Full JSpecify null‑safety support enables IDE warnings for potential NPEs when used with Java 17+ nullable annotations.

Migration checklist – five key steps

1. Dependency upgrade

Containers: Tomcat 11+ / Jetty 12+

Data layer: Hibernate 7+, Jackson 3+ (Jackson 2.x deprecated)

Testing: JUnit 6+ (Spring 6’s JUnit 5 remains compatible but migration is recommended)

2. Code changes – three mandatory modifications

Replace all javax. imports with jakarta. equivalents (e.g., jakarta.servlet.http.HttpServletRequest).

Remove RestTemplate usage; adopt WebClient or @HttpExchange.

Delete XML configuration files and migrate to Java Config (e.g., replace applicationContext.xml with @Configuration classes).

3. Critical test scenarios

Concurrent asynchronous logic (virtual threads may alter the existing thread model).

Transaction boundaries (Spring 7 refines transaction propagation).

AOP aspects (annotation caching may affect execution order).

4. Special‑case adaptations

Cache: ConcurrentReferenceHashMap lock‑contention issue is fixed; no extra tuning needed for high concurrency.

Reactive: Netty header adapter returns an empty list instead of null, so null checks must be removed.

Interceptors: Exception logs now clearly identify the failing interceptor, improving debugging efficiency.

Upgrade decision

Upgrade recommended when:

Running Spring Boot 4 (which mandates Spring 7).

Needing native‑image deployment with GraalVM.

Building high‑concurrency reactive applications (WebFlux performance boost).

Requiring built‑in API version management or a declarative HTTP client.

Consider staying on the current version when:

The project runs stably on Spring 5/6 with no new feature requirements.

Dependencies have not moved to Jakarta EE 11 (e.g., older MyBatis not compatible with JPA 3.2).