Bug Report: `spring.cloud.gcp.storage.host` Drops Port Number

[sejoung]

Bug Report: spring.cloud.gcp.storage.host Drops Port Number

Describe the bug

When configuring spring.cloud.gcp.storage.host with a custom port
(e.g. for a local emulator), the port number is silently removed by
GcpStorageAutoConfiguration.

Specifically, the verifyAndFetchHost() method reconstructs the host
using URL.getHost(), which strips the port portion of the URL.

This makes it impossible to connect to a GCS emulator running on a
non-default port.

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Affected Code

File: GcpStorageAutoConfiguration.java
Module: spring-cloud-gcp-autoconfigure
Relevant lines: 94, 103--118

// line 94
storageOptionsBuilder.setHost(verifyAndFetchHost(this.host));

// line 103-118
private String verifyAndFetchHost(String host) {
    URL url;
    try {
        url = new URL(host);
    } catch (MalformedURLException e) {
        throw new IllegalArgumentException(
            "Invalid host format: " + host
            + ". Please verify that the specified host follows the "
            + "'https://${service}.${universeDomain}/' format");
    }
    return url.getProtocol() + "://" + url.getHost() + "/";  // <-- BUG: port is lost
}

---

Problem

URL.getHost() returns only the hostname without the port.

As a result:

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Input Expected Actual

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http://localhost:54321 http://localhost:54321/ http://localhost/

---

The port is removed, leading to connection failures when using a local
emulator.

---

Impact

This directly affects integration testing scenarios using
fake-gcs-server + Testcontainers, where the container port is
dynamically mapped.

Example:

val endpoint = "http://${gcsContainer.host}:${gcsContainer.getMappedPort(4443)}"
// e.g. "http://localhost:54321"

After passing through verifyAndFetchHost(), the endpoint becomes:

http://localhost/

This results in:

Connection refused

---

Proposed Fix

Replace url.getHost() with url.getAuthority() to preserve the port:

Before (current behavior -- buggy)

return url.getProtocol() + "://" + url.getHost() + "/";

After (proposed fix)

return url.getProtocol() + "://" + url.getAuthority() + "/";

URL.getAuthority() correctly returns:

• host:port when a port is present
• host when no port is specified

This preserves compatibility in both cases.

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How to Reproduce

A minimal reproducible example is available here:

👉 https://github.com/sejoung/GCSTestContainter.git

Steps:

1. Clone the repository
2. Run:

<!-- -->

./gradlew test

What happens:

1. TestGcsContainterConfiguration starts a fake-gcs-server
   container on a random mapped port.

2. The application sets:

   spring.cloud.gcp.storage.host=http://localhost:<random-port>
   

3. GcpStorageAutoConfiguration processes the host and removes the
   port.

4. The Storage client attempts to connect to:

   http://localhost/
   

5. The test fails with Connection refused.

---

Environment

• Spring Cloud GCP: 7.4.5
• Spring Boot: 3.5.6
• Testcontainers: 1.21.3
• fake-gcs-server: latest
• Java: 24

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Please let me know if you would like me to submit a PR once this issue
is reviewed and labeled as Accepting Contributions.