[[kotlin-config]]
= Kotlin Configuration
Spring Security Kotlin configuration has been available since Spring Security 5.3.
It lets users configure Spring Security by using a native Kotlin DSL.

[NOTE]
====
Spring Security provides https://github.com/spring-projects/spring-security-samples/tree/main/servlet/spring-boot/kotlin/hello-security[a sample application] to demonstrate the use of Spring Security Kotlin Configuration.
====

[[kotlin-config-httpsecurity]]
== HttpSecurity

How does Spring Security know that we want to require all users to be authenticated?
How does Spring Security know we want to support form-based authentication?
There is a configuration class (called `SecurityFilterChain`) that is being invoked behind the scenes.
It is configured with the following default implementation:

====
[source,kotlin]
----
@Bean
open fun filterChain(http: HttpSecurity): SecurityFilterChain {
   http {
        authorizeRequests {
            authorize(anyRequest, authenticated)
        }
       formLogin { }
       httpBasic { }
    }
    return http.build()
}
----
====

The default configuration (shown in the preceding listing):

* Ensures that any request to our application requires the user to be authenticated
* Lets users authenticate with form-based login
* Lets users authenticate with HTTP Basic authentication

Note that this configuration is parallels the XML namespace configuration:

====
[source,xml]
----
<http>
	<intercept-url pattern="/**" access="authenticated"/>
	<form-login />
	<http-basic />
</http>
----
====

== Multiple HttpSecurity Instances

We can configure multiple HttpSecurity instances, just as we can have multiple `<http>` blocks.
The key is to register multiple `SecurityFilterChain` `@Bean`s.
The following example has a different configuration for URL's that start with `/api/`:

====
[source,kotlin]
----
@EnableWebSecurity
class MultiHttpSecurityConfig {
    @Bean                                                            <1>
    public fun userDetailsService(): UserDetailsService {
        val users: User.UserBuilder = User.withDefaultPasswordEncoder()
        val manager = InMemoryUserDetailsManager()
        manager.createUser(users.username("user").password("password").roles("USER").build())
        manager.createUser(users.username("admin").password("password").roles("USER","ADMIN").build())
        return manager
    }

    @Order(1)                                                        <2>
    @Bean
    open fun apiFilterChain(http: HttpSecurity): SecurityFilterChain {
        http {
            securityMatcher("/api/**")                               <3>
            authorizeRequests {
                authorize(anyRequest, hasRole("ADMIN"))
            }
            httpBasic { }
        }
        return http.build()
    }

    @Bean                                                            <4>
    open fun formLoginFilterChain(http: HttpSecurity): SecurityFilterChain {
        http {
            authorizeRequests {
                authorize(anyRequest, authenticated)
            }
            formLogin { }
        }
        return http.build()
    }
}
----

<1> Configure Authentication as usual.
<2> Create an instance of `SecurityFilterChain` that contains `@Order` to specify which `SecurityFilterChain` should be considered first.
<3> The `http.antMatcher` states that this `HttpSecurity` is applicable only to URLs that start with `/api/`
<4> Create another instance of `SecurityFilterChain`.
If the URL does not start with `/api/`, this configuration is used.
This configuration is considered after `apiFilterChain`, since it has an `@Order` value after `1` (no `@Order` defaults to last).
====