Spring Boot WebFlux 3.0.3 results in the hostname "0:0:0:0:0:0:0:1"

[davidmelia]

Describe the bug

After upgrading from Spring Boot WebFlux 3.0.2 to Spring Boot WebFlux 3.0.3 I am getting an odd hostname:

To Reproduce
I have a super simple spring boot 3.0.3 project in https://github.com/davidmelia/open-api-issues-hostname

Navigating to http://localhost:8080/webjars/swagger-ui/index.html#/home-controller/home you can see the odd hostname

Expected behavior

if you downgrade to boot 3.0.2 in the pom you get the usual hostname:

[programista-zacny]

I have the same problem but I reproduce it a little bit different.

My properties:

springdoc.api-docs.path=/api-docs
springdoc.swagger-ui.path=/swagger-ui

When I open url http://127.0.0.1:8080/api-docs everything is working fine.
When I try http://localhost:8080/api-docs I have an error:

java.lang.IllegalArgumentException: URLDecoder: Illegal hex characters in escape (%) pattern - Error at index 1 in: "0]"

Temurin JDK17, URLDecoder.java:235, param String s -> http://[0:0:0:0:0:0:0:1%0]:8080/api-docs
I'm using newest up-to-date Linux Manjaro.

[JohnNiang]

This might be caused by spring-projects/spring-framework@5847454.

[aperusset]

Hi everyone !

I have exactly the same issue with Spring Boot 3.0.3, running on Ubuntu 20.04.5 LTS.

Additionnaly, it causes some issues with actuator/prometheus, as the URLs are shown in my browser with IPV6 localhost resolution :

{
  "_links": {
    "self": {
       "href": "http://[0:0:0:0:0:0:0:1%250]:9321/metrics",
       "templated": false
  },
  ...
}

I was able to quick fix this by adding these properties to my application.yml file :

server.address: 127.0.0.1
management.server.address: 127.0.0.1

Another solution is to add a command line argument to the JVM : -Djava.net.preferIPv4Stack=true

Does anyone openend an issue to Spring Framework repository or find a "real" fix ?

Edit : just found the related issue spring-projects/spring-framework#30033

[JohnNiang]

Just upgrade Spring Boot 3.0.4 to solve this problem.

[bnasslahsen]

It's a spring-boot issue.
spring-boot 3.0.4 resolves this issue!