Spring Cloud 整合Sentinel

Spring Cloud 整合 Alibaba Sentinel 主要涉及以下几个步骤：

1. 引入 Sentinel 依赖
2. 配置 Sentinel 控制台信息
3. 配置 Sentinel 的限流规则
4. 使用注解定义需要保护的资源
5. 使用 Sentinel 提供的 API 进行编程式限流

以下是一个简单的示例，展示如何在 Spring Cloud 应用中整合 Sentinel：

1. 在 pom.xml 中添加 Sentinel 依赖

<dependencies>
    <!-- Sentinel 依赖 -->
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
    </dependency>
</dependencies>

2. application.yml 配置文件中添加 Sentinel 控制台信息

spring:
  cloud:
    sentinel:
      transport:
        dashboard: 127.0.0.1:8080 # Sentinel 控制台地址
        port: 8719 # 默认端口，若冲突需更改

3. 配置限流规则

import com.alibaba.csp.sentinel.annotation.aspectj.SentinelResourceAspect;
import com.alibaba.csp.sentinel.slots.block.RuleConstant;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
import com.alibaba.csp.sentinel.slots.block.flow.FlowRuleManager;
 
import java.util.ArrayList;
import java.util.List;
 
public class SentinelConfiguration {
 
    public SentinelConfiguration() {
        initFlowRules();
    }
 
    private void initFlowRules() {
        List<FlowRule> rules = new ArrayList<>();
        FlowRule rule = new FlowRule();
        rule.setResource("myResource"); // 需要限流的资源名
        rule.setGrade(RuleConstant.FLOW_GRADE_QPS); // 限流规则为每秒的请求量
        rule.setCount(1); // 限制为每秒1次请求
        rules.add(rule);
 
        FlowRuleManager.loadRules(rules);
    }
}

4. 使用注解定义资源

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
public class TestController {
 
    @GetMapping("/test")
    @SentinelResource(value = "myResource", blockHandler = "handleException")
    public String test() {
        return "Hello Sentinel";
    }
 
    public String handleException(BlockException ex) {
        return "Too many requests";
    }
}

5. 编程式限流

import com.alibaba.csp.sentinel.Entry;
import com.alibaba.csp.sentinel.SphU;
import com.alibaba.csp.sentinel.Tracer;
import com.alibaba.csp.sentinel.context.ContextUtil;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.RuleConstant