/*
 * Copyright 2012-2018 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.autoconfigure.security.oauth2.resource.servlet;

import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.oauth2.jwt.JwtDecoder;

/**
 * {@link WebSecurityConfigurerAdapter} for OAuth2 resource server support.
 *
 * @author Madhura Bhave
 */
@Configuration
@ConditionalOnMissingBean(WebSecurityConfigurerAdapter.class)
class OAuth2ResourceServerWebSecurityConfiguration {

	@Configuration
	@ConditionalOnBean(JwtDecoder.class)
	static class OAuth2WebSecurityConfigurerAdapter extends WebSecurityConfigurerAdapter {

		protected void configure(HttpSecurity http) throws Exception {
			http.authorizeRequests().anyRequest().authenticated().and().oauth2()
					.resourceServer().jwt();
		}

	}

}

/*
 * Copyright 2012-2018 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.autoconfigure.security.oauth2.resource.servlet;

import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.oauth2.jwt.JwtDecoder;

/**
 * {@link WebSecurityConfigurerAdapter} for OAuth2 resource server support.
 *
 * @author Madhura Bhave
 */
@Configuration
@ConditionalOnMissingBean(WebSecurityConfigurerAdapter.class)
class OAuth2ResourceServerWebSecurityConfiguration {

	@Configuration
	@ConditionalOnBean(JwtDecoder.class)
	static class OAuth2WebSecurityConfigurerAdapter extends WebSecurityConfigurerAdapter {

		@Override
		protected void configure(HttpSecurity http) throws Exception {
			http.authorizeRequests().anyRequest().authenticated().and().oauth2()
					.resourceServer().jwt();
		}

	}

}

Add missing @Override