Update credential erasure examples

Closes gh-15683

Author: sjohnr

docs/modules/ROOT/pages/servlet/authentication/passwords/index.adoc

@@ -326,10 +326,74 @@ Normally, Spring Security builds an `AuthenticationManager` internally composed
 In certain cases, it may still be desired to customize the instance of `AuthenticationManager` used by Spring Security.
 For example, you may need to simply disable xref:servlet/authentication/architecture.adoc#servlet-authentication-providermanager-erasing-credentials[credential erasure] for cached users.
 
-The recommended way to do this is to simply publish your own `AuthenticationManager` bean, and Spring Security will use it.
-You can publish an `AuthenticationManager` using the following configuration:
+To do this, you can take advantage of the fact that the `AuthenticationManagerBuilder` used to build Spring Security's global `AuthenticationManager` is published as a bean.
+You can configure the builder as follows:
+
+.Configure global `AuthenticationManagerBuilder`
+[tabs]
+=====
+Java::
++
+[source,java,role="primary"]
+----
+@Configuration
+@EnableWebSecurity
+public class SecurityConfig {
+
+	@Bean
+	public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
+		// ...
+		return http.build();
+	}
+
+	@Bean
+	public UserDetailsService userDetailsService() {
+		// Return a UserDetailsService that caches users
+		// ...
+	}
+
+	@Autowired
+	public void configure(AuthenticationManagerBuilder builder) {
+		builder.eraseCredentials(false);
+	}
+
+}
+----
+
+Kotlin::
++
+[source,kotlin,role="secondary"]
+----
+import org.springframework.security.config.annotation.web.invoke
 
-.Publish `AuthenticationManager` bean for Spring Security
+@Configuration
+@EnableWebSecurity
+class SecurityConfig {
+
+	@Bean
+	fun securityFilterChain(http: HttpSecurity): SecurityFilterChain {
+		// ...
+		return http.build()
+	}
+
+	@Bean
+	fun userDetailsService(): UserDetailsService {
+		// Return a UserDetailsService that caches users
+		// ...
+	}
+
+	@Autowired
+	fun configure(builder: AuthenticationManagerBuilder) {
+		builder.eraseCredentials(false)
+	}
+
+}
+----
+=====
+
+Alternatively, you may configure a local `AuthenticationManager` to override the global one.
+
+.Configure local `AuthenticationManager` for Spring Security
 [tabs]
 =====
 Java::
@@ -344,31 +408,27 @@ public class SecurityConfig {
 	public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
 		http
 			.authorizeHttpRequests((authorize) -> authorize
-				.requestMatchers("/login").permitAll()
 				.anyRequest().authenticated()
 			)
 			.httpBasic(Customizer.withDefaults())
-			.formLogin(Customizer.withDefaults());
+			.formLogin(Customizer.withDefaults())
+			.authenticationManager(authenticationManager());
 
 		return http.build();
 	}
 
-	@Bean
-	public AuthenticationManager authenticationManager(
-			UserDetailsService userDetailsService,
-			PasswordEncoder passwordEncoder) {
+	private AuthenticationManager authenticationManager() {
 		DaoAuthenticationProvider authenticationProvider = new DaoAuthenticationProvider();
-		authenticationProvider.setUserDetailsService(userDetailsService);
-		authenticationProvider.setPasswordEncoder(passwordEncoder);
+		authenticationProvider.setUserDetailsService(userDetailsService());
+		authenticationProvider.setPasswordEncoder(passwordEncoder());
 
 		ProviderManager providerManager = new ProviderManager(authenticationProvider);
 		providerManager.setEraseCredentialsAfterAuthentication(false);
 
 		return providerManager;
 	}
 
-	@Bean
-	public UserDetailsService userDetailsService() {
+	private UserDetailsService userDetailsService() {
 		UserDetails userDetails = User.withDefaultPasswordEncoder()
 			.username("user")
 			.password("password")
@@ -378,8 +438,7 @@ public class SecurityConfig {
 		return new InMemoryUserDetailsManager(userDetails);
 	}
 
-	@Bean
-	public PasswordEncoder passwordEncoder() {
+	private PasswordEncoder passwordEncoder() {
 		return PasswordEncoderFactories.createDelegatingPasswordEncoder();
 	}
 
@@ -390,8 +449,7 @@ XML::
 +
 [source,xml,role="secondary"]
 ----
-<http>
-	<intercept-url pattern="/login" access="permitAll"/>
+<http authentication-manager-ref="authenticationManager">
 	<intercept-url pattern="/**" access="authenticated"/>
 	<form-login />
 	<http-basic />
@@ -431,32 +489,29 @@ class SecurityConfig {
 	fun securityFilterChain(http: HttpSecurity): SecurityFilterChain {
 		http {
 			authorizeHttpRequests {
-				authorize("/login", permitAll)
 				authorize(anyRequest, authenticated)
 			}
 			formLogin { }
 			httpBasic { }
+			authenticationManager = authenticationManager()
 		}
 
 		return http.build()
 	}
 
 	@Bean
-	fun authenticationManager(
-			userDetailsService: UserDetailsService,
-			passwordEncoder: PasswordEncoder): AuthenticationManager {
+	fun authenticationManager(): AuthenticationManager {
 		val authenticationProvider = DaoAuthenticationProvider()
-		authenticationProvider.setUserDetailsService(userDetailsService)
-		authenticationProvider.setPasswordEncoder(passwordEncoder)
+		authenticationProvider.setUserDetailsService(userDetailsService())
+		authenticationProvider.setPasswordEncoder(passwordEncoder())
 
 		val providerManager = ProviderManager(authenticationProvider)
 		providerManager.eraseCredentialsAfterAuthentication = false
 
 		return providerManager
 	}
 
-	@Bean
-	fun userDetailsService(): UserDetailsService {
+	private fun userDetailsService(): UserDetailsService {
 		val user = User.withDefaultPasswordEncoder()
 			.username("user")
 			.password("password")
@@ -466,76 +521,11 @@ class SecurityConfig {
 		return InMemoryUserDetailsManager(user)
 	}
 
-	@Bean
-	fun passwordEncoder(): PasswordEncoder {
+	private fun passwordEncoder(): PasswordEncoder {
 		return PasswordEncoderFactories.createDelegatingPasswordEncoder()
 	}
 
 }
 ----
 =====
 
-Alternatively, you can take advantage of the fact that the `AuthenticationManagerBuilder` used to build Spring Security's global `AuthenticationManager` is published as a bean.
-You can configure the builder as follows:
-
-.Configure global `AuthenticationManagerBuilder`
-[tabs]
-=====
-Java::
-+
-[source,java,role="primary"]
-----
-@Configuration
-@EnableWebSecurity
-public class SecurityConfig {
-
-	@Bean
-	public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
-		// ...
-		return http.build();
-	}
-
-	@Bean
-	public UserDetailsService userDetailsService() {
-		// Return a UserDetailsService that caches users
-		// ...
-	}
-
-	@Autowired
-	public void configure(AuthenticationManagerBuilder builder) {
-		builder.eraseCredentials(false);
-	}
-
-}
-----
-
-Kotlin::
-+
-[source,kotlin,role="secondary"]
-----
-import org.springframework.security.config.annotation.web.invoke
-
-@Configuration
-@EnableWebSecurity
-class SecurityConfig {
-
-	@Bean
-	fun securityFilterChain(http: HttpSecurity): SecurityFilterChain {
-		// ...
-		return http.build()
-	}
-
-	@Bean
-	fun userDetailsService(): UserDetailsService {
-		// Return a UserDetailsService that caches users
-		// ...
-	}
-
-	@Autowired
-	fun configure(builder: AuthenticationManagerBuilder) {
-		builder.eraseCredentials(false)
-	}
-
-}
-----
-=====