Upgrading from Spring Boot 3 to Spring Boot 4 - Minor issues

With the new release of Spring AI 2.0 I have no more excuse to migrate one of my biggest pet projects from Spring Boot 3.5.0 + AI 1.0 to Spring Boot 4.1.0 + AI 2.0.

The base framework changes from Spring 6.2 to Spring framework 7.0.

Every major update brings some benefits and potential issues, with this migration from SB 3.5 to 4 I encountered some minor issues. My pet project is not an enterprise application, the security level is not complex like a Spring Security + SSO with MS Entra + external access that usually creates a lot of headaches, but the application is quite big and comparable to some enterprise applications.

The official migration guide can be found here:

Spring Boot 4.0 Migration Guide

Spring Boot helps you to create Spring-powered, production-grade applications and services with absolute minimum fuss. - spring-projects/spring-boot

GitHubspring-projects

List of the issues and remediations

Swagger dependency

I use a lot of Swagger annotations to document the API, these are not automatically imported anymore. To avoid a build error like io.swagger.v3.oas.annotations.media.Schema not found you need to import the library manually in your pom.xml

<!-- OpenAPI / Swagger annotations used by ActivityRunDto -->
  <dependency>
    <groupId>org.springdoc</groupId>
    <artifactId>springdoc-openapi-starter-webmvc-ui</artifactId>
    <version>3.0.3</version>
  </dependency>

AI tool import

The package org.springframework.ai.tool.annotation does not exist the dependency needs to be imported explicitly

<dependency>
    <groupId>org.springframework.ai</groupId>
    <artifactId>spring-ai-model</artifactId>
</dependency>

Ai Client

Another dependency has been moved out: package org.springframework.ai.chat.client does not exist, it can be easily fixed:

<dependency>
    <groupId>org.springframework.ai</groupId>
    <artifactId>spring-ai-client-chat</artifactId>
</dependency>

Security Auto Configuration:

The build had failed with this error: package org.springframework.boot.autoconfigure.security.servlet does not exist this is not a major issue, in fact I was excluding this Spring feature : @SpringBootApplication(exclude = {UserDetailsServiceAutoConfiguration.class}) . With the new version is enough to remove the exclusion.

UriComponentsBuilder

Cannot find symbol fromHttpUrl

This problem is self-explanatory and a quick refactoring solved the problem. Spring simply changed the method name from fromHttpUrl to fromUriString

RestResponseException

Cannot find symbol getRawStatusCode

Another minor issue, a quick refactoring to getStatusCode fixed the issue.

@WebMvcTest

Yes I have tests in pet projects too, usually is the best method to learn the intricacies of the Spring framework.
Errors: package org.springframework.boot.test.autoconfigure.web.servlet does not exist. @WebMvcTestand @AutoConfigureMockMvcare gone, but luckily not too distant. The annotations moved from

org.springframework.boot.test.autoconfigure.web.servlet

to

org.springframework.boot.webmvc.test.autoconfigure

this requires to import into the pom:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webmvc-test</artifactId>
    <scope>test</scope>
</dependency>

This required an 'Invalidate Caches ...' in my IntelliJ instance to work correctly ... ☹️ ... still nothing compared with a project using Gradle.

WebMvcTest ... part 2

Spring Boot 4 is more strict in some checks and many tests failed, requiring some code rewrite.StructuredAuthenticationEntryPoint needs a real Jackson bean to render the 401 JSON body, @EnableCaching means a CacheManager must exist in the test context.

Cache

A component required a bean of type 'org.springframework.cache.CacheManager' that could not be found.
My project is using a backend cache to improve the performance of the recurring requests. Spring Boot 4 is more modular and moved the CacheManagerin a dedicated starter:

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

Jackson 2 to Jackson 3 upgrade

Spring upgraded the Jackson dependency, this created some issues because I had a direct import of jackson-databindin the pom. Spring was expecting Jackson 3 objects but was receiving still objects with the old version.

I had to remove the explicit dependency:

<!-- Jackson -->
  <dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
</dependency>

... and replace import com.fasterxml.jackson.databind.ObjectMapper;with import tools.jackson.databind.ObjectMapper;

Next step, code upgrade

The upgrade adds more features to the AI library and allows to introduce @JSpecify for the null management. I'll write a dedicated post with the changes.