一、下载sentinel-dashboard控制台应用并在8080端口启动
二、项目添加springboot 和dubbo相关依赖（降级规则并未持久化，如果需要持久化，如果需要持久化降级规则，只需增加nacos相关依赖并在nacos中进行配置，然后配置application.properties或application.yml)
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>dubbo-service-provider2</artifactId>
<version>1.0-SNAPSHOT</version>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>8</source>
<target>8</target>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<dubbo.version>3.1.8</dubbo.version>
<spring-boot.version>2.7.10</spring-boot.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.7.10</version>
</dependency>
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo</artifactId>
<version>${dubbo.version}</version>
</dependency>
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-dependencies-zookeeper</artifactId>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-registry-nacos</artifactId>
</dependency>
<dependency>
<groupId>com.alibaba.csp</groupId>
<artifactId>sentinel-apache-dubbo-adapter</artifactId>
<version>1.8.7</version>
</dependency>
<dependency>
<groupId>com.alibaba.csp</groupId>
<artifactId>sentinel-transport-simple-http</artifactId>
<version>1.8.7</version>
</dependency>
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>${spring-boot.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-bom</artifactId>
<version>${dubbo.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-dependencies-zookeeper</artifactId>
<version>${dubbo.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>2021.0.1</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-alibaba-dependencies</artifactId>
<version>2021.0.1.0</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
</project>
三、配置文件
server:
port: 9811
dubbo:
application:
name: dubbo-springboot-demo-provider
protocol:
name: dubbo
port: 28095
registry:
address: zookeeper://xx.xx.xx.xx:2181
四、配置jvm参数
-Djava.net.perferIPv4Stack=true
-Dcsp.sentinel.api.port=8720
-Dcsp.sentinel.dashboard.server=localhost:8080
-Dproject.name=spring-cloud-sentinel-dubbo-provider
五、定义服务接口、服务实现（其中服务实现中故意制造出了除零异常用来测试降级，handleException方法是降级时被调用的方法）
package cn.edu.tju.service;
public interface DemoService {
String sayHello(String name);
}
package cn.edu.tju.service;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.degrade.DegradeException;
import com.google.gson.JsonObject;
import org.apache.dubbo.config.annotation.DubboService;
import java.util.Date;
@DubboService(loadbalance = "")
public class DemoServiceImpl implements DemoService {
@SentinelResource(value = "sayHello", fallback = "handleException")
public String sayHello(String name) {
int t = 1/0;
return "Hay " + name;
}
public String handleException(String name,Throwable ex) {
String className = ex.getClass().getName();
if(className.equals("com.alibaba.csp.sentinel.slots.block.degrade.DegradeException")){
JsonObject jsonObject=new JsonObject();
jsonObject.addProperty("code",500);
jsonObject.addProperty("message","降级原因:"+ex.getMessage()+" "+ex.getClass().getName());
return jsonObject.toString();
}
else {
JsonObject jsonObject=new JsonObject();
jsonObject.addProperty("code",500);
jsonObject.addProperty("message","异常原因:"+ex.getMessage()+" "+ex.getClass().getName());
return jsonObject.toString();
}
}
}
六、在sentinel-dashboard控制台配置降级规则
其中资源名要和接口实现中方法上@SentinelResource注解上的value值相同
七、客户端调用dubbo服务sayHello接口，满足降级的条件后，将从接口获取到类似如下的响应（其中getDubbo这个接口调用了上面的sayHello接口）
可见降级规则起作用了
