Spring Cloud Starter Gateway and SpringBoot 4.0.0

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Summary

A senior engineer encountered a cryptic dependency resolution failure when attempting to upgrade an API Gateway project to Spring Boot 4.0.1. The build failed with the error Could not find org.springframework.cloud:spring-cloud-starter-gateway:. The root cause was a combination of mismatched Spring Cloud and Spring Boot versions and a missing explicit version declaration for the gateway artifact in the build.gradle.kts file. Although the spring-cloud-dependencies BOM (Bill of Materials) was imported, the version used (2025.1.0) was not compatible with the requested Spring Boot version, and the specific gateway starter artifact was not correctly resolved by Gradle.

Root Cause

The specific error Could not find org.springframework.cloud:spring-cloud-starter-gateway: (notice the trailing colon) indicates that Gradle resolved the group and artifact name but failed to resolve the version.

There were two specific configuration issues in the build.gradle.kts file:

  • Incompatible BOM Version: The dependencyManagement block imported spring-cloud-dependencies:2025.1.0. Spring Boot 4.0.0 (and the specific 4.0.1 used) is extremely new. The 2025.1.0 release train of Spring Cloud is likely not compatible with Spring Boot 4.x yet and was likely targeting a different Boot version (likely 3.x).
  • Missing Explicit Version: Because the imported BOM was likely incompatible, Gradle could not find a version for spring-cloud-starter-gateway within that BOM. Since the dependency declaration implementation("org.springframework.cloud:spring-cloud-starter-gateway") lacked an explicit version, the build failed.

Why This Happens in Real Systems

Dependency management in large microservices often becomes fragile during major upgrades.

  • BOM Lag: Spring Cloud release trains (2024.0.0, 2025.1.0) are tightly coupled to Spring Boot versions. Spring Boot 4 represents a significant jump (Jakarta EE 17), and Spring Cloud needs time to adapt.
  • Gradle Resolution Strategy: If a BOM is applied but fails to provide a version for a specific artifact (due to incompatibility or exclusion), Gradle falls back to the configuration, finds no version, and fails the build.
  • Toolchain Misdirection: The developer configured Java 25 (toolchain { languageVersion = JavaLanguageVersion.of(25) }). While valid, this adds a variable if the local environment or CI pipeline does not support Java 25, potentially triggering secondary resolution errors.

Real-World Impact

  • Blocked Deployment: The CI/CD pipeline halts immediately, preventing the release of the API Gateway.
  • Developer Velocity Loss: Time is wasted debugging dependency trees rather than working on business logic.
  • Version Hell: Manually bumping versions without verifying compatibility can lead to runtime errors (e.g., NoSuchMethodError) if incompatible libraries are forced to link.

Example or Code

The dependencyManagement block and the implementation line are the culprits.

plugins {
    application
    java
    id("org.springframework.boot") version "4.0.1"
    id("io.spring.dependency-management") version "1.1.7"
    kotlin("jvm") version "2.1.10"
    kotlin("plugin.spring") version "2.1.10"
}

dependencies {
    // The problematic line causing the build error
    implementation("org.springframework.cloud:spring-cloud-starter-gateway")

    // Other dependencies...
    implementation("org.springframework.boot:spring-boot-starter-oauth2-client")
    implementation("org.springframework.cloud:spring-cloud-starter-netflix-eureka-client:5.0.0")
    implementation("org.springframework.cloud:spring-cloud-starter-kubernetes-client-all")

    testImplementation("org.springframework.boot:spring-boot-starter-test")
    testImplementation("io.projectreactor:reactor-test")
    testImplementation("junit:junit:4.13.2")
}

dependencyManagement {
    imports {
        // The BOM version causing the incompatibility
        val springCloudVersion = "2025.1.0"
        mavenBom("org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}")
    }
}

How Senior Engineers Fix It

To resolve this, a senior engineer performs the following steps:

  1. Consult the Compatibility Matrix: Check the official Spring Cloud project page to find the version of Spring Cloud that supports Spring Boot 4.0.x.
  2. Align the BOM: Update the spring-cloud-dependencies version in the dependencyManagement block to a version known to support Spring Boot 4.0.x (e.g., 2025.0.0 or 2024.0.x if available, or a milestone release specifically targeting Boot 4).
  3. Remove Hardcoded Versions: Remove any explicit versions from the dependencies block that are managed by the BOM (like spring-cloud-starter-gateway) to let the BOM manage them.
  4. Verify Java Version: Ensure the Java toolchain matches what is supported by the specific Spring Boot 4 release (likely Java 17 or 21 minimum, though 25 is cutting edge).

Corrected Configuration Strategy:

dependencyManagement {
    imports {
        // Verify this version actually supports Boot 4.0.1
        val springCloudVersion = "2025.0.0" // Example fix
        mavenBom("org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}")
    }
}

dependencies {
    // Now resolved by the BOM
    implementation("org.springframework.cloud:spring-cloud-starter-gateway")
}

Why Juniors Miss It

  • Over-reliance on Auto-Completion: Juniors often copy dependency snippets from tutorials or StackOverflow without verifying the versions against their specific spring-boot-starter-parent version.
  • Lack of BOM Understanding: They may not understand that a BOM (Bill of Materials) acts as a central version controller. They assume adding the BOM guarantees all children will work, failing to realize the BOM itself must be compatible with the parent framework.
  • Ignoring the Trailing Colon: The error message Could not find ...gateway:. ends with a colon. A senior engineer recognizes this pattern instantly as a version resolution failure. A junior might just think the dependency is “missing” and try to find a different artifact name.