SpringCloud Alibaba Sentinel 降级（支持RestTemplate）

# 开启或关闭 @SentinelRestTemplate 注解
resttemplate:
  sentinel:
    enabled: true

/**
 * <h1>开启服务间的调用保护, 需要给 RestTemplate 做一些包装</h1>
 * */
@Slf4j
@Configuration
public class SentinelConfig {

    /**
     * <h2>包装 RestTemplate</h2>
     * */
    @Bean
//    @SentinelRestTemplate(
//            fallback = "handleFallback", fallbackClass = RestTemplateExceptionUtil.class,
//            blockHandler = "handleBlock", blockHandlerClass = RestTemplateExceptionUtil.class
//    )
    public RestTemplate restTemplate() {
        return new RestTemplate();  // 可以对其做一些业务相关的配置
    }
}

import com.alibaba.cloud.sentinel.rest.SentinelClientHttpResponse;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.fastjson.JSON;
import com.imooc.ecommerce.vo.JwtToken;
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.HttpRequest;
import org.springframework.http.client.ClientHttpRequestExecution;

/**
 * <h1>RestTemplate 在限流或异常时的兜底方法</h1>
 * */
@Slf4j
public class RestTemplateExceptionUtil {

    /**
     * <h2>限流后的处理方法</h2>
     * */
    public static SentinelClientHttpResponse handleBlock(HttpRequest request,
                                                         byte[] body,
                                                         ClientHttpRequestExecution execution,
                                                         BlockException ex) {
        log.error("Handle RestTemplate Block Exception: [{}], [{}]",
                request.getURI().getPath(), ex.getClass().getCanonicalName());
        return new SentinelClientHttpResponse(
                JSON.toJSONString(new JwtToken("qinyi-imooc-block"))
        );
    }

    /**
     * <h2>异常降级之后的处理方法</h2>
     * */
    public static SentinelClientHttpResponse handleFallback(HttpRequest request,
                                                            byte[] body,
                                                            ClientHttpRequestExecution execution,
                                                            BlockException ex) {
        log.error("Handle RestTemplate Fallback Exception: [{}], [{}]",
                request.getURI().getPath(), ex.getClass().getCanonicalName());
        return new SentinelClientHttpResponse(
                JSON.toJSONString(new JwtToken("qinyi-imooc-block"))
        );
    }
}

import com.alibaba.fastjson.JSON;
import com.imooc.ecommerce.vo.JwtToken;
import com.imooc.ecommerce.vo.UsernameAndPassword;
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * <h1>使用 Sentinel 保护 RestTemplate 服务间调用</h1>
 * */
@Slf4j
@RestController
@RequestMapping("/sentinel-rest-template")
public class SentinelRestTemplateController {

    private final RestTemplate restTemplate;

    public SentinelRestTemplateController(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    /**
     * <h2>从授权服务中获取 JwtToken</h2>
     * 1. 流控降级:
     * 是针对于簇点链路中的 http://127.0.0.1:7000/ecommerce-authority-center/authority/token
     * 2. 容错降级: 对于服务不可用时不能生效
     * */
    @PostMapping("/get-token")
    public JwtToken getTokenFromAuthorityService(
            @RequestBody UsernameAndPassword usernameAndPassword) {

        String requestUrl =
                "http://127.0.0.1:7000/ecommerce-authority-center/authority/token";
        log.info("RestTemplate request url and body: [{}], [{}]",
                requestUrl, JSON.toJSONString(usernameAndPassword));

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        return restTemplate.postForObject(
                requestUrl,
                new HttpEntity<>(JSON.toJSONString(usernameAndPassword), headers),
                JwtToken.class
        );
    }
}