SpringCloud 中通過 Feign 呼叫其他服務，當服務使用 Oauth2 授權的時候，Feign 預設並不會將認證的 TOKEN 帶在請求的 Header 中，需要手動實現傳遞 TOKEN 的配置；通過實現feign.RequestInterceptor來實現自定義新增認證資訊

• FeignOauth2RequestInterceptor.java

import feign.RequestInterceptor;
import feign.RequestTemplate;
import lombok.extern.slf4j.Slf4j;
import org.springframework.security.core.Authentication;
import
 
 org.springframework.security.core.context.SecurityContext;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.oauth2.provider.authentication.OAuth2AuthenticationDetails;
import org.springframework.context.annotation.Configuration;

@Configuration
 

public class FeignOauth2RequestInterceptor implements RequestInterceptor {

    private final String AUTHORIZATION_HEADER = "Authorization";
    private final String BEARER_TOKEN_TYPE = "Bearer";

    @Override
    public void apply(RequestTemplate requestTemplate) {
        SecurityContext securityContext = SecurityContextHolder.getContext();
        Authentication authentication = securityContext.getAuthentication();
        if
 
 (authentication != null && authentication.getDetails() instanceof OAuth2AuthenticationDetails) {
            OAuth2AuthenticationDetails details = (OAuth2AuthenticationDetails) authentication.getDetails();
            requestTemplate.header(AUTHORIZATION_HEADER, String.format("%s %s", BEARER_TOKEN_TYPE, details.getTokenValue()));
        }

    }
}

這樣就可以將請求的認證資訊放入到 Header 中，通過認證