前期准备：
启动nacos和sentinel
提供者9003/9004 （以9003为样本）
新建cloudalibaba-provider-payment9003/9004
pom文件
mscloud03
com.atguigu.springcloud
1.0-SNAPSHOT
4.0.0
cloudalibaba-provider-payment9003
com.alibaba.cloud
spring-cloud-starter-alibaba-nacos-discovery
com.atguigu.springcloud
cloud-api-commons
${project.version}
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-actuator
org.springframework.boot
spring-boot-devtools
runtime
true
org.projectlombok
lombok
true
org.springframework.boot
spring-boot-starter-test
test
yml文件
server:
port: 9003
spring:
application:
name: nacos-payment-provider
cloud:
nacos:
discovery:
server-addr: localhost:8848 #配置Nacos地址
management:
endpoints:
web:
exposure:
include: '*'配置9004的时候记得修改端口
主启动类
@SpringBootApplication
@EnableDiscoveryClient
public class PaymentMain9003
{
public static void main(String[] args) {
SpringApplication.run(PaymentMain9003.class, args);
}
}业务类
@RestController
public class PaymentController
{
@Value("${server.port}")
private String serverPort;
public static HashMap hashMap = new HashMap<>();
static
{
hashMap.put(1L,new Payment(1L,"28a8c1e3bc2742d8848569891fb42181"));
hashMap.put(2L,new Payment(2L,"bba8c1e3bc2742d8848569891ac32182"));
hashMap.put(3L,new Payment(3L,"6ua8c1e3bc2742d8848569891xt92183"));
}
@GetMapping(value = "/paymentSQL/{id}")
public CommonResult paymentSQL(@PathVariable("id") Long id)
{
Payment payment = hashMap.get(id);
CommonResult result = new CommonResult(200,"from mysql,serverPort: "+serverPort,payment);
return result;
}
} 测试1
启动9003访问
消费者84
新建cloudalibaba-consumer-nacos-order84
pom文件
mscloud03
com.atguigu.springcloud
1.0-SNAPSHOT
4.0.0
cloudalibaba-consumer-nacos-order84
com.alibaba.cloud
spring-cloud-starter-alibaba-nacos-discovery
com.alibaba.cloud
spring-cloud-starter-alibaba-sentinel
com.atguigu.springcloud
cloud-api-commons
${project.version}
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-actuator
org.springframework.boot
spring-boot-devtools
runtime
true
org.projectlombok
lombok
true
org.springframework.boot
spring-boot-starter-test
test
yml文件
server:
port: 84
spring:
application:
name: nacos-order-consumer
cloud:
nacos:
discovery:
server-addr: localhost:8848
sentinel:
transport:
#配置Sentinel dashboard地址
dashboard: localhost:8080
#默认8719端口，假如被占用会自动从8719开始依次+1扫描,直至找到未被占用的端口
port: 8719
#消费者将要去访问的微服务名称(注册成功进nacos的微服务提供者)
service-url:
nacos-user-service: http://nacos-payment-provider主启动
@EnableDiscoveryClient
@SpringBootApplication
public class OrderNacosMain84
{
public static void main(String[] args) {
SpringApplication.run(OrderNacosMain84.class, args);
}
}配置类
@Configuration
public class ApplicationContextConfig
{
@Bean
@LoadBalanced
public RestTemplate getRestTemplate()
{
return new RestTemplate();
}
}业务类1
@RestController
@Slf4j
public class CircleBreakerController
{
public static final String SERVICE_URL = "http://nacos-payment-provider";
@Resource
private RestTemplate restTemplate;
@RequestMapping("/consumer/fallback/{id}")
@SentinelResource(value = "fallback")
public CommonResult fallback(@PathVariable Long id)
{
CommonResult result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
if (id == 4) {
throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
}else if (result.getData() == null) {
throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
}
return result;
}
} 测试2
启动9003 9004 84
访问
再访问
可以发现第一次是9004端口，第二次是9003端口，这里面的话，就可以就知道意见实现了ribbon中的轮训
测试3
给客户error页面，不友好
修改业务类（只配置fallback）
@RestController
@Slf4j
public class CircleBreakerController
{
public static final String SERVICE_URL = "http://nacos-payment-provider";
@Resource
private RestTemplate restTemplate;
@RequestMapping("/consumer/fallback/{id}")
@SentinelResource(value = "fallback",fallback = "handlerFallback") //fallback负责业务异常
public CommonResult fallback(@PathVariable Long id)
{
CommonResult result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
if (id == 4) {
throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
}else if (result.getData() == null) {
throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
}
return result;
}
public CommonResult handlerFallback(@PathVariable Long id,Throwable e) {
Payment payment = new Payment(id,"null");
return new CommonResult<>(444,"兜底异常handlerFallback,exception内容 "+e.getMessage(),payment);
}
} 
本例sentinel无配置
测试4
这里可以发现没有出现error界面，而是我们自己配置的兜底的处理方案
修改业务类（只配置blockHandler ）
@RestController
@Slf4j
public class CircleBreakerController
{
public static final String SERVICE_URL = "http://nacos-payment-provider";
@Resource
private RestTemplate restTemplate;
@RequestMapping("/consumer/fallback/{id}")
@SentinelResource(value = "fallback",blockHandler = "blockHandler") //blockHandler负责在sentinel里面配置的降级限流
public CommonResult fallback(@PathVariable Long id)
{
CommonResult result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
if (id == 4) {
throw new IllegalArgumentException ("非法参数异常....");
}else if (result.getData() == null) {
throw new NullPointerException ("NullPointerException,该ID没有对应记录");
}
return result;
}
public CommonResult handlerFallback(@PathVariable Long id,Throwable e) {
Payment payment = new Payment(id,"null");
return new CommonResult<>(444,"fallback,无此流水,exception "+e.getMessage(),payment);
}
public CommonResult blockHandler(@PathVariable Long id,BlockException blockException) {
Payment payment = new Payment(id,"null");
return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException "+blockException.getMessage(),payment);
}
} 
配置sentinel 
测试5
修改业务类（fallback和blockHandler都配置）
@RestController
@Slf4j
public class CircleBreakerController
{
public static final String SERVICE_URL = "http://nacos-payment-provider";
@Resource
private RestTemplate restTemplate;
@RequestMapping("/consumer/fallback/{id}")
@SentinelResource(value = "fallback",fallback = "handlerFallback",blockHandler = "blockHandler")
public CommonResult fallback(@PathVariable Long id)
{
CommonResult result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
if (id == 4) {
throw new IllegalArgumentException ("非法参数异常....");
}else if (result.getData() == null) {
throw new NullPointerException ("NullPointerException,该ID没有对应记录");
}
return result;
}
public CommonResult handlerFallback(@PathVariable Long id,Throwable e) {
Payment payment = new Payment(id,"null");
return new CommonResult<>(444,"fallback,无此流水,exception "+e.getMessage(),payment);
}
public CommonResult blockHandler(@PathVariable Long id,BlockException blockException) {
Payment payment = new Payment(id,"null");
return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException "+blockException.getMessage(),payment);
}
} 
测试 6
再访问的时候，那就意味着这个时候会被限流处理
若 blockHandler 和 fallback 都进行了配置，则被限流降级而抛出 BlockException 时只会进入 blockHandler 处理逻辑。
修改业务类（忽略属性.......）
@RestController
@Slf4j
public class CircleBreakerController
{
public static final String SERVICE_URL = "http://nacos-payment-provider";
@Resource
private RestTemplate restTemplate;
@RequestMapping("/consumer/fallback/{id}")
@SentinelResource(value = "fallback", fallback = "handlerFallback", blockHandler = "blockHandler",
exceptionsToIgnore = {IllegalArgumentException.class})
public CommonResult fallback(@PathVariable Long id)
{
CommonResult result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id,CommonResult.class,id);
if (id == 4) {
throw new IllegalArgumentException ("非法参数异常....");
}else if (result.getData() == null) {
throw new NullPointerException ("NullPointerException,该ID没有对应记录");
}
return result;
}
public CommonResult handlerFallback(@PathVariable Long id,Throwable e) {
Payment payment = new Payment(id,"null");
return new CommonResult<>(444,"fallback,无此流水,exception "+e.getMessage(),payment);
}
public CommonResult blockHandler(@PathVariable Long id,BlockException blockException) {
Payment payment = new Payment(id,"null");
return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException "+blockException.getMessage(),payment);
}
} 
测试7
