要实现一个OAuth2授权服务器，可以使用以下步骤：

1. 添加相关依赖

   
       org.springframework.boot
       spring-boot-starter-security
   
   
       org.springframework.boot
       spring-boot-starter-oauth2-authorization-server
   
   

2. 创建一个配置类来配置授权服务器

   import org.springframework.context.annotation.Configuration;
   import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
   import org.springframework.security.config.annotation.web.builders.HttpSecurity;
   import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
   import org.springframework.security.oauth2.config.annotation.builders.InMemoryClientDetailsServiceBuilder;
   import org.springframework.security.oauth2.config.annotation.configurers.ClientDetailsServiceConfigurer;
   import org.springframework.security.oauth2.config.annotation.web.configuration.EnableAuthorizationServer;
   import org.springframework.security.oauth2.config.annotation.web.configurers.AuthorizationServerEndpointsConfigurer;
   
   @Configuration
   @EnableAuthorizationServer
   public class AuthorizationServerConfig extends WebSecurityConfigurerAdapter {
   
       @Override
       protected void configure(HttpSecurity http) throws Exception {
           http
               .authorizeRequests()
               .antMatchers("/oauth/token").permitAll()
               .anyRequest().authenticated()
               .and()
               .csrf().disable();
       }
   
       @Override
       protected void configure(AuthenticationManagerBuilder auth) throws Exception {
           auth.inMemoryAuthentication()
               .withUser("user")
               .password("{noop}password")
               .roles("USER");
       }
   
       @Override
       public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
           InMemoryClientDetailsServiceBuilder builder = clients.inMemory();
           builder
               .withClient("client")
               .secret("{noop}secret")
               .authorizedGrantTypes("password", "authorization_code", "refresh_token")
               .scopes("read", "write")
               .accessTokenValiditySeconds(3600)
               .refreshTokenValiditySeconds(86400);
       }
   
       @Override
       public void configure(AuthorizationServerEndpointsConfigurer endpoints) throws Exception {
           endpoints.authenticationManager(authenticationManager());
       }
   }
   

3. 创建一个启动类

   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   
   @SpringBootApplication
   public class OAuth2AuthorizationServerApplication {
   
       public static void main(String[] args) {
           SpringApplication.run(OAuth2AuthorizationServerApplication.class, args);
       }
   }
   

以上代码示例了如何创建一个基本的OAuth2授权服务器，使用了Spring Security和Spring Boot的相关功能。配置类AuthorizationServerConfig负责配置授权服务器的行为，包括设置访问规则、用户认证和客户端信息等。启动类OAuth2AuthorizationServerApplication用于启动应用程序。

请注意，这只是一个简单的示例，实际使用中可能需要根据具体需求进行更详细的配置和自定义。