从java访问Spring OAuth2授权服务器端点时出现问题

<dependency>
    <groupId>org.springframework.security.oauth.boot</groupId>
    <artifactId>spring-security-oauth2-autoconfigure</artifactId>
    <version>2.5.0</version>
</dependency>

spring.security.oauth2.client.registration.<clientId>.client-id=<client_id>
spring.security.oauth2.client.registration.<clientId>.client-secret=<client_secret>
spring.security.oauth2.client.registration.<clientId>.redirect-uri=<redirect_uri>
spring.security.oauth2.client.registration.<clientId>.authorization-grant-type=authorization_code
spring.security.oauth2.client.registration.<clientId>.scope=<scope>
spring.security.oauth2.client.provider.<provider>.issuer-uri=<issuer_uri>

RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);

MultiValueMap<String, String> body = new LinkedMultiValueMap<>();
body.add("grant_type", "authorization_code");
body.add("code", "<authorization_code>");
body.add("redirect_uri", "<redirect_uri>");
body.add("client_id", "<client_id>");
body.add("client_secret", "<client_secret>");

HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(body, headers);
ResponseEntity<String> response = restTemplate.postForEntity("<authorization_server_url>", request, String.class);

String accessToken = response.getBody();