Fix invalid security example in doc

Closes gh-8580

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -2685,26 +2685,12 @@ annotation will cause it to be decorated and enhanced with the necessary pieces
 the `/login` path working. For example, here we simply allow unauthenticated access
 to the home page at "/" and keep the default for everything else:
 
+
 [source,java,indent=0]
 ----
-	@Configuration
-	public class WebSecurityConfiguration extends WebSecurityConfigurerAdapter {
-
-		@Override
-		public void init(WebSecurity web) {
-			web.ignore("/");
-		}
-
-		@Override
-		protected void configure(HttpSecurity http) throws Exception {
-			http.antMatcher("/**").authorizeRequests().anyRequest().authenticated();
-		}
-
-	}
+include::{code-examples}/web/security/UnAuthenticatedAccessExample.java[tag=configuration]
 ----
 
-
-
 [[boot-features-security-actuator]]
 === Actuator Security
 If the Actuator is also in use, you will find:

spring-boot-docs/src/main/java/org/springframework/boot/web/security/UnAuthenticatedAccessExample.java

+/*
+ * Copyright 2012-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.web.security;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.builders.WebSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+
+/**
+ * Example configuration for using a {@link WebSecurityConfigurerAdapter} to configure unauthenticated access
+ * to the home page at "/"
+ *
+ * @author Robert Stern
+ */
+public class UnAuthenticatedAccessExample {
+
+    // tag::configuration[]
+    /**
+     * {@link WebSecurityConfigurerAdapter} that provides init to configure
+     * {@link WebSecurity} argument to customize access rules
+     */
+    @Configuration
+    static class WebSecurityConfiguration extends WebSecurityConfigurerAdapter {
+
+        @Override
+        public void init(WebSecurity web) {
+            web.ignoring().antMatchers("/");
+        }
+
+        @Override
+        protected void configure(HttpSecurity http) throws Exception {
+            http.antMatcher("/**").authorizeRequests().anyRequest().authenticated();
+        }
+    }
+}