如何通过SpringBoot从Keycloak获取访问令牌？

<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-spring-boot-starter</artifactId>
</dependency>

keycloak.realm=your-realm
keycloak.auth-server-url=https://your-keycloak-server/auth
keycloak.resource=your-client-id
keycloak.credentials.secret=your-client-secret

import org.keycloak.OAuth2Constants;
import org.keycloak.adapters.springsecurity.client.KeycloakRestTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Component;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;

@Component
public class KeycloakTokenProvider {
    
    @Autowired
    private KeycloakRestTemplate keycloakRestTemplate;
    
    @Value("${keycloak.resource}")
    private String clientId;
    
    @Value("${keycloak.credentials.secret}")
    private String clientSecret;
    
    @Value("${keycloak.auth-server-url}")
    private String keycloakUrl;
    
    public String getAccessToken() {
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
        
        MultiValueMap<String, String> body = new LinkedMultiValueMap<>();
        body.add(OAuth2Constants.GRANT_TYPE, "client_credentials");
        body.add(OAuth2Constants.CLIENT_ID, clientId);
        body.add(OAuth2Constants.CLIENT_SECRET, clientSecret);
        
        HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<>(body, headers);
        
        ResponseEntity<AccessTokenResponse> responseEntity = keycloakRestTemplate.postForEntity(
                keycloakUrl + "/realms/{realm}/protocol/openid-connect/token",
                requestEntity,
                AccessTokenResponse.class,
                "your-realm"
        );
        
        AccessTokenResponse response = responseEntity.getBody();
        return response.getAccessToken();
    }
}

@RestController
public class MyController {
    
    @Autowired
    private KeycloakTokenProvider tokenProvider;
    
    @GetMapping("/api/data")
    public String getData() {
        String accessToken = tokenProvider.getAccessToken();
        
        // 使用访问令牌进行后续操作
        // ...
        
        return "Data";
    }
}