Spring Security An error was found in 9.19 --- gezq0714

Describe the bug Hello，SpringSecurity. Today, when I use SpringBoot:2.5.4 and SpringSecurity:5.5.2 to build SpringBootAdmin Server，I found a error!

To Reproduce Just a simple project with SpringBoot Initializr, add spring-security and spring-boot-admin-server in pom.xml, and copy a sample in Spring Boot Admin Reference Guide (codecentric.github.io), a error will occur when you start run the SpringBoot project.

Expected behavior

The error log is as follows：

The bean 'springSecurityFilterChain', defined in class path resource 
[org/springframework/boot/actuate/autoconfigure/security/reactive/ReactiveManagementWebSecurityAutoConfiguration.class], could not be registered.
A bean with that name has already been defined in class path resource 
[org/springframework/security/config/annotation/web/configuration/WebSecurityConfiguration.class] and overriding is disabled.

Sample You can find the sample in gezq0714 repository, The following links： gezq0714/spring-boot-2.5.4-demo: SpringSecurity5.5.2 with SpringBoot2.5.4 occur a error demo (github.com)

Comment From: marcusdacoregio

Hi, @gezq0714.

This error is happening because the spring-boot-admin-server from codecentric is using a reactive approach, while your application is Servlet-based. You can see in the log that the ReactiveManagementWebSecurityAutoConfiguration is trying to create the bean: [org/springframework/boot/actuate/autoconfigure/security/reactive/ReactiveManagementWebSecurityAutoConfiguration.class], could not be registered.

Since you've defined the bean using a Servlet-approach, the beans collide, the reactive auto-configuration looks for a SecurityWebFilterChain instead of a SecurityFilterChain.

What I suggest is that you implement your application using the reactive approach or search for a Servlet-based spring-boot-admin-server.