将Spring Boot版本从1.5.4更新到2.1.1后，为什么在交换授权代码后却得到空访问令牌？

Question

在将Spring Boot版本从1.5.4更新到2.1.1之后，交换授权代码后，我得到了空访问令牌

   Spring security class:
    @Configuration
    @EnableWebSecurity
    public class SpringSecurityConfiguration extends WebSecurityConfigurerAdapter {       

        @Bean
        @Override
        public AuthenticationManager authenticationManagerBean() throws Exception {
            return super.authenticationManagerBean();
        }

        @Override
        public void configure(WebSecurity web) throws Exception {
            web.ignoring().antMatchers("/users/signup");
            web.ignoring().antMatchers("/voice/test");
        }   

        @Override
        protected void configure(HttpSecurity http) throws Exception {
            http.authorizeRequests().antMatchers("/").permitAll().antMatchers(Constants.PROTECTED_RESOURCES)
                .hasAnyRole("ADMIN").anyRequest().authenticated().and().formLogin()
                .permitAll().and().logout().permitAll();        

            http.csrf().disable();       
        }   
    }

Athorization server class:    
@Configuration
    @EnableAuthorizationServer
    public class AuthorizationServerConfiguration extends AuthorizationServerConfigurerAdapter {        

        @Autowired
        private AuthenticationManager authenticationManager; 
        @Autowired
        private RedisConnectionFactory connectionFactory; 
        @Autowired
        private TokenStore tokenStore;
        @Autowired
        private UserDetailsServiceImpl userDetailsServiceImpl;
        @Autowired
        private AuthenticationProviderImpl authenticationProviderImpl;
        @Autowired
        private DataSource dataSource;  

        @Bean
        public TokenStore tokenStore() {
            return new RedisTokenStore(connectionFactory);
        }   

        @Bean
        public TokenStore tokenStore1() {
            return new JdbcTokenStore(dataSource);
        } 

        @Override
        public void configure(ClientDetailsServiceConfigurer configurer) throws Exception {
            configurer.jdbc(dataSource);
        }   

        @Override
        public void configure(AuthorizationServerSecurityConfigurer oauthServer) throws Exception {
            oauthServer.tokenKeyAccess("permitAll()")
            .checkTokenAccess("isAuthenticated()");
        }    

        protected void configure(AuthenticationManagerBuilder auth) throws Exception {
            auth.authenticationProvider(authenticationProviderImpl);        
        }

        @Override
        public void configure(AuthorizationServerEndpointsConfigurer endpoints) throws Exception {

            endpoints.authenticationManager(authenticationManager);
            endpoints.userDetailsService(userDetailsServiceImpl);
            endpoints.tokenStore(tokenStore);
        }
    }

controller of client end:   
 @GetMapping("/welcome")
        public String welcome(@RequestParam("code") String code) throws JsonProcessingException, IOException {      

            ResponseEntity<String> response = null;     
            System.out.println("Authorization Code------" + code);
            RestTemplate restTemplate = new RestTemplate();

            String credentials = "phynart-client:phynart-secret";
            String encodedCredentials = new String(Base64.encodeBase64(credentials.getBytes()));

            HttpHeaders headers = new HttpHeaders();
            headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
            headers.add("Authorization", "Basic " + encodedCredentials);

            HttpEntity<String> request = new HttpEntity<String>(headers);

            String access_token_url = "http://localhost:8080/oauth/token";
            access_token_url += "?code=" + code;
            access_token_url += "&grant_type=authorization_code";
            access_token_url += "&redirect_uri=http://localhost:8888/welcome";

            response = restTemplate.exchange(access_token_url, HttpMethod.POST, request, String.class);              
            System.out.println("Access Token Response ---------" + response.getBody());     
            return "welcome";
        }
    }


client JSP page:   
 <%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <title>Home</title>
    </head>
    <body>
        <h3>Home Page</h3>

        <div id="home">
            <form:form action="http://localhost:8080/oauth/authorize"
                method="post" modelAttribute="user">
                <p>               
                     <input type="text" name="response_type" value="code" /> 
                     <input type="text" name="client_id" value="phynart-client" />
                     <input type="text" name="redirect_uri" value="http://localhost:8888/welcome" />
                     <input type="text" name="scope" value="read" />                 
                     <input type="SUBMIT" value="Login" /> <br> 
            </form:form>
          </div>      
    </body>
    </html>

我得到的响应为空访问令牌响应，有人可以帮助我吗？在更新Spring Boot之前，它可以正常工作，并且在交换授权代码后，我正在获取访问令牌，但是现在它返回null作为响应，请让我知道是否需要添加任何其他东西来使其正常工作。是安全性Config类，授权服务器，重定向身份验证代码的控制器和具有所有客户端详细信息的jsp页面...