SpringCloud快速入门

Spring Cloud

单一应用架构 ：主要解决ORM 数据库访问层。
垂直应用架构 ： 解决分层问题，实现应用的分层开发，提升开发效率。
分布式应用架构：解决系统间调用问题，引发了SOA（面向服务开发）架构新潮。
SOA治理（Macro Service治理）：对面向服务开发和治理同时提出新的挑战，要求应用能够做到容易部署、智能路由、服务负载均衡、熔断等要求，能够做到对服务的可视化治理等。

伴随着互联网的发展，人们对这种微服务的开发的呼声越来越大，在互联网的萌芽了两款重量级的SOA治理框架阿里巴巴Dubbo和SpringFrameWork提供的SpringCloud由于Spring的广大使用群体也间接的使的Spring Cloud的市场占用率一路飙升。阿里巴巴的Dubbo也开始发力，由于阿里巴巴的优秀的技术团队和国内较高的知名度，也对Dubbo框架的发展起到一定的推广的作用，但是相比较于SpringCloud而言，dubbo由于易用性上和对程序员的要求都比Spring Cloud要高一些，因此目前很多互联网公司在做微服务组件开发的时候一般还是使用SpringCloud居多。

Spring Cloud Ribbon 组件 -负载均衡

Spring Cloud Ribbon 是一个基于Http和TCP的客服端负载均衡工具，它是基于Netflix Ribbon实现的。通过SpringCloud的自动配置使得项目可以自动的给RestTemplate添加拦截器。

基于配置文件

• 在项目中集成ribbon

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Greenwich.SR1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>
<dependencies>
    ....
    <!--ribbon-->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
    </dependency>
</dependencies>

• 配置类中添加@LoadBalanced注解

@SpringBootApplication
public class UserApplciation {
    public static void main(String[] args) {
        SpringApplication.run(UserApplciation.class,args);
    }
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(){
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate;
    }
}

ribbon底层会将RestTemplate进行加强，实质上是对RestTemplate添加拦截器，用于修改URL中的服务名。

• application.properties

server.port=8887
USER-SERVER.ribbon.listOfServers=localhost:8889,localhost:8888
USER-SERVER.ribbon.NFLoadBalancerRuleClassName=com.netflix.loadbalancer.RandomRule

• UserController

@RestController
@RequestMapping(value = "usermanager")
public class UserController {
    @Autowired
    private RestTemplate restTemplate;

    @GetMapping(value = "/queryUserById")
    public User queryUserById(@RequestParam(value = "id") Integer id){
        String url="http://USER-SERVER/formUserManager/queryUserById?id={id}";
        return restTemplate.getForObject(url,User.class,id);
    }
}

这里的缺点是服务器的地址是配置死的，一旦配置的服务节点上线|下线都有可能影响本应用，我们期望该listOfServers可以动态变更，达到服务节点的热部署。

基于注解类

• RibbonConfigure

@Configuration
public class RibbonConfigure {
    @Bean
    public ServerList<Server> ribbonServerList(){
        Server server1 = new Server("localhost", 8888);

        Server server2 = new Server("localhost", 8889);
        return new StaticServerList<Server>(server1,server2);
    }

    @Bean
    public IRule ribbonRule(){
        return new RandomRule();
    }
}

这里的缺点是服务器的地址是配置死的，一旦配置的服务节点上线|下线都有可能影响本应用，我们期望该ribbonServerList可以动态变更，达到服务节点的热部署。

• UserApplciation

@SpringBootApplication
@RibbonClient(name = "USER-SERVICE",configuration = {RibbonConfigure.class})
public class UserApplciation {
    public static void main(String[] args) {
        SpringApplication.run(UserApplciation.class,args);
    }
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(){
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate;
    }
}

• UserController

@RestController
@RequestMapping(value = "usermanager")
public class UserController {
    @Autowired
    private RestTemplate restTemplate;

    @GetMapping(value = "/queryUserById")
    public User queryUserById(@RequestParam(value = "id") Integer id){
        String url="http://USER-SERVER/formUserManager/queryUserById?id={id}";
        return restTemplate.getForObject(url,User.class,id);
    }
}

Spring Cloud Eureka (服务注册中心)

Spring Cloud Eureka 是 Spring Cloud Netflix 微服务套件中的一部分， 它基于 Netflix Eureka 做了二次封装， 主要负责完成微服务架构中的服务治理功能。 Spring Cloud 通过为Eureka 增加了 Spring Boot 风格的自动化配置，我们只需通过简单引入依赖和注解配置就能让 Spring Boot构建的微服务应用轻松地与 Eureka 服务治理体系进行整合。

Eureka注册中心集群构建

• pom.xml

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.5.RELEASE</version>
</parent>
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Greenwich.SR1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>
<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

• 启动配置类

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class,args);
    }
}

• application-eureka-1.properties

server.port=1111

# 指定当前注册中心的服务名称
spring.application.name=eurekaregistry

## 启用注册中心主动失效，并且每次主动失效检测间隔为5s 默认值60s
eureka.server.eviction-interval-timer-in-ms= 5000
## 设置eureka注册中心的响应更新时间
eureka.server.responseCacheUpdateIntervalMs=3000
eureka.server.responseCacheAutoExpirationInSeconds=60

## 配置注册中心的主机名
eureka.instance.instance-id = eureka-1
eureka.instance.hostname = CentOSA
## 服务刷新时间配置，每隔这个时间会主动心跳一次
eureka.instance.lease-renewal-interval-in-seconds= 5
## 服务提供者被认定为丢失心跳超时，失效多久后被删除
eureka.instance.lease-expiration-duration-in-seconds=15

## 配置定时获取|抓取注册中心的数据时间
eureka.client.registry-fetch-interval-seconds= 5
eureka.client.instance-info-replication-interval-seconds= 5
## 配置集群中其他eureka实例，用于本eureka实例的注册方。
eureka.client.region=beijing
eureka.client.availability-zones.beijing=zone-2,zone-3
eureka.client.service-url.zone-2=http://CentOSB:1111/eureka/
eureka.client.service-url.zone-3=http://CentOSC:1111/eureka/

• application-eureka-2.properties

server.port=1111

# 指定当前注册中心的服务名称
spring.application.name=eurekaregistry

## 启用注册中心主动失效，并且每次主动失效检测间隔为5s 默认值60s
eureka.server.eviction-interval-timer-in-ms= 5000
## 设置eureka注册中心的响应更新时间
eureka.server.responseCacheUpdateIntervalMs=3000
eureka.server.responseCacheAutoExpirationInSeconds=60

## 配置注册中心的主机名
eureka.instance.instance-id = eureka-2
eureka.instance.hostname = CentOSB
## 服务刷新时间配置，每隔这个时间会主动心跳一次
eureka.instance.lease-renewal-interval-in-seconds= 5
## 服务提供者被认定为丢失心跳超时，失效多久后被删除
eureka.instance.lease-expiration-duration-in-seconds=15

## 配置定时获取|抓取注册中心的数据时间
eureka.client.registry-fetch-interval-seconds= 5
eureka.client.instance-info-replication-interval-seconds= 5
## 配置集群中其他eureka实例，用于本eureka实例的注册方。
eureka.client.region=beijing
eureka.client.availability-zones.beijing=zone-1,zone-3
eureka.client.service-url.zone-1=http://CentOSA:1111/eureka/
eureka.client.service-url.zone-3=http://CentOSC:1111/eureka/

• application-eureka-3.properties

server.port=1111

# 指定当前注册中心的服务名称
spring.application.name=eurekaregistry

## 启用注册中心主动失效，并且每次主动失效检测间隔为5s 默认值60s
eureka.server.eviction-interval-timer-in-ms= 5000
## 设置eureka注册中心的响应更新时间
eureka.server.responseCacheUpdateIntervalMs=3000
eureka.server.responseCacheAutoExpirationInSeconds=60

## 配置注册中心的主机名
eureka.instance.instance-id = eureka-3
eureka.instance.hostname = CentOSC
## 服务刷新时间配置，每隔这个时间会主动心跳一次
eureka.instance.lease-renewal-interval-in-seconds= 5
## 服务提供者被认定为丢失心跳超时，失效多久后被删除
eureka.instance.lease-expiration-duration-in-seconds=15

## 配置定时获取|抓取注册中心的数据时间
eureka.client.registry-fetch-interval-seconds= 5
eureka.client.instance-info-replication-interval-seconds= 5
## 配置集群中其他eureka实例，用于本eureka实例的注册方。
eureka.client.region=beijing
eureka.client.availability-zones.beijing=zone-1,zone-2
eureka.client.service-url.zone-1=http://CentOSA:1111/eureka/
eureka.client.service-url.zone-2=http://CentOSB:1111/eureka/

• Maven package指令打包

mvn package 

• 上传eurekacloud-1.0-SNAPSHOT.jar到CentOSA、CentOSB、CentOSC

[root@CentOSA ~]# java -jar eurekacloud-1.0-SNAPSHOT.jar --spring.profiles.active=eureka-1
[root@CentOSB ~]# java -jar eurekacloud-1.0-SNAPSHOT.jar --spring.profiles.active=eureka-2
[root@CentOSC ~]# java -jar eurekacloud-1.0-SNAPSHOT.jar --spring.profiles.active=eureka-3

• 访问浏览器查看Eureka是否启动成功

Eureka自我保护机制

由于Eureka再设计上遵循AP原则，一旦Eureka服务节点检测到异常Renews < Renews threshold(心跳阈值< 接收心跳)Eureka会进入自我保护机制。一旦进入自我保护机制，Eureka就会失去剔除失效节点功能（失去检测功能）。

• Renews threshold: eureka.server.renewal-percent-threshold= 0.85
  集群: (2 x n) x eureka.server.renewal-percent-threshold = (2 * 3) *0.85 = 5.1 = 取 5
  单机: 2 × (n+1) × eureka.server.renewal-percent-threshold = 4 * 0.85 = 3.4 取 3

• 默认自我保护机制是开启的（推荐选项）

• eureka.server.enable-self-preservation=true
  如果是单机模式很容易触发自我保护，因为
  Renews threshold= 2 （1+1） 0.85 = 3
  Renews (last min) =（ 60 / eureka.instance.lease-renewal-interval-in-seconds=30)* 1 = 2

• 所以如果构建的是单机版本的Eureka，建议大家关闭自我保护机制。

服务提供方注册服务

• 发布服务

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Greenwich.SR1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

• 配置服务发布信息

# 发布服务
spring.application.name=USER-SERVICE
# 发布服务实例id
eureka.instance.instance-id=001 
eureka.instance.prefer-ip-address=true
eureka.instance.lease-renewal-interval-in-seconds=10
eureka.instance.lease-expiration-duration-in-seconds=20

# 只单纯的注册服务，并不获取服务注册列表信息
eureka.client.register-with-eureka=true
eureka.client.healthcheck.enabled=true
eureka.client.fetch-registry=false
eureka.client.service-url.defaultZone=http://CentOSA:1111/eureka/,http://CentOSB:1111/eureka/,http://CentOSC:1111/eureka/

服务引用方引用服务

• pom.xml

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Greenwich.SR1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>
<!--引入 eureka后，无需再次引入Ribbon-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

• application.peroperties

# 只是单纯的获取注册中心的注册信息，并不注册自己
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=true
eureka.client.service-url.defaultZone=http://CentOSA:1111/eureka/,http://CentOSB:1111/eureka/,http://CentOSC:1111/eureka/

Spring Cloud Hystrix (熔断器)

Hystrix是一个延迟和容错库，旨在隔离对远程系统，服务和第三方库的访问点，停止级联故障，并在复杂的分布式系统中实现弹性，在这些系统中，故障是不可避免的。

熔断器集成

• pom.xml

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.5.RELEASE</version>
</parent>
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Greenwich.SR1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    </dependency>
</dependencies>

• 在需要熔断的方法是添加@HystrixComand注解

@HystrixCommand
@Override
public Integer sum(Integer x, Integer y) {
    System.out.println("thread:"+Thread.currentThread().getId());
    int b=10/0;
    return (x+y)*2;
}

• 在启动类上添加@EnableCircuitBreaker

@SpringBootApplication
@EnableCircuitBreaker
public class HystrixSpringBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(HystrixSpringBootApplication.class,args);
    }
}

线程隔离

默认该方法的执行会启动新的线程执行和主程序不在一个线程中，因此如果上下文中存在ThreadLocal变量，在该方法中就失效了。因此一般可以通过设置commandProperties注解属性，设置线程就可以了。

@HystrixCommand(commandProperties = {
            @HystrixProperty(name = "execution.isolation.strategy",value = "SEMAPHORE")
    })
@Override
public User queryUserById(Integer id) {
    System.out.println(Thread.currentThread().getId());
    return userDAO.queryById(id);
}

execution.isolation.strategy该属性的可选值有两个THREAD和SEMAPHORE默认值是THREAD.①一般如果一个实例一秒钟有100个并发，此时因为频繁启动线程的开销过大此时一般考虑使用SEMAPHORE，②非网络调用。

Fallback

过在@HystrixCommand中声明fallbackMethod的名称可以实现优雅降级，如下所示：

@HystrixCommand(
    fallbackMethod = "failback4Sum",
    // ignoreExceptions = {ArithmeticException.class},
    commandProperties = {
        @HystrixProperty(name="execution.isolation.strategy",value="SEMAPHORE")
    }
)
@Override
public Integer sum(Integer x, Integer y) {
    System.out.println("thread:"+Thread.currentThread().getId());
    int b=10/0;
    return (x+y)*2;
}
public Integer failback4Sum(Integer x, Integer y,Throwable  e) {
    System.out.println(e.getMessage());
    return x+y;
}

注意要求fallbackMethod方法和目标方法必须在同一个类中，具有相同的参数（异常参数可选）

请求超时熔断

用户可以通过设置execution.isolation.thread.timeoutInMilliseconds属性设置一个方法最大请求延迟，系统会抛出HystrixTimeoutException

@HystrixCommand(
    fallbackMethod = "failback4Sum",
    commandProperties = {
        @HystrixProperty(name="execution.isolation.strategy",value="THREAD"),
        @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value = "100")
    }
)
@Override
public Integer sum(Integer x, Integer y) {
    try {
        int ms=new Random().nextInt(200);
        System.out.println("sleep:"+ms);
        Thread.sleep(ms);
    } catch (Exception e) {
        System.err.println(e.getMessage());
    }
    return (x+y)*2;
}
public Integer failback4Sum(Integer x, Integer y,Throwable  e) {
    return x+y;
}

熔断器限流

• 阅读：https://blog.csdn.net/tongtong_use/article/details/78611225

hystrix dashbord(监测)

• pom.ml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
</dependency>

• application.properties

# 开启健康检查的所有访问接口
management.endpoints.web.exposure.include=*

• HystrixSpringBootApplication

@SpringBootApplication
@EnableCircuitBreaker
@EnableHystrixDashboard
public class HystrixSpringBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(HystrixSpringBootApplication.class,args);
    }
}

• 访问 http://localhost:9999/hystrix

• 完整熔断器配置

@Service
public class UserService implements IUserService {

    public User failback4QueryUserById(Integer id) {
        return new User(-1,"服务降级！");
    }
    @HystrixCommand(
            fallbackMethod = "failback4QueryUserById",
            commandProperties = {
                    @HystrixProperty(name="execution.isolation.strategy",value="THREAD"),
                    @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value = "1000"),
                    // 时间窗口 必须是 numBuckets的整数倍数
                    @HystrixProperty(name="metrics.rollingStats.timeInMilliseconds",value = "10000"),//设置窗口长度10秒
                    @HystrixProperty(name="metrics.rollingStats.numBuckets",value = "10"),//设置窗口滑动间隔1s

                    //闸刀开启的条件 请求数> 2 && 错误率> 50%
                    @HystrixProperty(name="circuitBreaker.requestVolumeThreshold",value = "20"),//设置最小请求次数
                    @HystrixProperty(name="circuitBreaker.errorThresholdPercentage",value = "50"),//设置错误率50%
                    @HystrixProperty(name="circuitBreaker.sleepWindowInMilliseconds",value = "5000"),// 当全开到半开的时间间隔
            },
            threadPoolProperties = {
                    @HystrixProperty(name="coreSize",value="10"),//设置线程池大小
                    @HystrixProperty(name="queueSizeRejectionThreshold",value = "10")//设置队列最大等待请求数
            }

    )
    @Override
    public User queryUserById(Integer id) {
        int random = new Random().nextInt(3000);
        try {
            System.out.println("sleep:"+random);
            Thread.sleep(random);
        } catch (InterruptedException e) {

        }
        return new User(id,"user"+id);
    }
}

Spring Cloud OpenFeign(Rest客户端)

Feign是一个声明性的Web服务客户端。它使编写Web服务客户端变得更容易。Feign 增加了对Spring MVC注解的支持，并使用了Spring MVC中相同HttpMessageConverters。 Feign集成了Ribbon、Eureka、Hystrix，在使用Feign时提供负载均衡以及容错的的http客户端。

快速入门

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>1.8</java.version>
</properties>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.5.RELEASE</version>
</parent>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Greenwich.SR1</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
    </dependency>

</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

• application.properties

server.port=9999
# 配置Eureka 拦截参数
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=true
eureka.client.healthcheck.enabled=true
eureka.client.service-url.defaultZone=http://CentOSA:1111/eureka/,http://CentOSB:1111/eureka/,http://CentOSC:1111/eureka/

• UserFeignControllerClient

@FeignClient(name = "USER-SERVICE")
public interface UserFeignControllerClient {
    @PostMapping(value = "/formUserManager/addUser")
    @ResponseBody
    public void addUser(User user) throws IOException;

    @GetMapping(value = "/formUserManager/queryUserById")
    @ResponseBody
    public User queryUserById(@RequestParam(value = "id") Integer id);

    @GetMapping(value = "/formUserManager/queryUserByPage")
    @ResponseBody
    public Map<String, Object> queryUserByPage(@RequestParam(value = "page", defaultValue = "1") Integer pageNow,
                                               @RequestParam(value = "rows", defaultValue = "10") Integer pageSize,
                                               @RequestParam(value = "column", required = false) String column,
                                               @RequestParam(value = "value", required = false) String value);

    @DeleteMapping(value = "/formUserManager/delteUserByIds")
    @ResponseBody
    public void delteUserByIds(@RequestParam(value = "ids") Integer[] ids);

    @PutMapping(value = "/formUserManager/updateUser")
    @ResponseBody
    public void updateUser(User user) throws IOException;
}

• FeignSpringBootApplication

@SpringBootApplication
@EnableFeignClients
public class FeignSpringBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(FeignSpringBootApplication.class,args);
    }
}

配置熔断

默认Feign没有开启熔断策略，需要用户在配置文件中指定

• application.properties

server.port=9999

eureka.client.register-with-eureka=false
eureka.client.fetch-registry=true
eureka.client.healthcheck.enabled=true
eureka.client.service-url.defaultZone=http://CentOSA:1111/eureka/,http://CentOSB:1111/eureka/,http://CentOSC:1111/eureka/

# 开启hystrix
feign.hystrix.enabled=true
#　配置服务访问超时
feign.client.config.USER-SERVICE.connect-timeout=100
feign.client.config.USER-SERVICE.read-timeout=100

• 修改UserFeignControllerClient，添加failback属性

@FeignClient(name = "USER-SERVICE",fallback = UserFeignControllerFailBack.class)
public interface UserFeignControllerClient {
    @PostMapping(value = "/formUserManager/addUser")
    @ResponseBody
    public void addUser(User user) throws IOException;

    @GetMapping(value = "/formUserManager/queryUserById")
    @ResponseBody
    public User queryUserById(@RequestParam(value = "id") Integer id);

    @GetMapping(value = "/formUserManager/queryUserByPage")
    @ResponseBody
    public Map<String, Object> queryUserByPage(@RequestParam(value = "page", defaultValue = "1") Integer pageNow,
                                               @RequestParam(value = "rows", defaultValue = "10") Integer pageSize,
                                               @RequestParam(value = "column", required = false) String column,
                                               @RequestParam(value = "value", required = false) String value);

    @DeleteMapping(value = "/formUserManager/delteUserByIds")
    @ResponseBody
    public void delteUserByIds(@RequestParam(value = "ids") Integer[] ids);

    @PutMapping(value = "/formUserManager/updateUser")
    @ResponseBody
    public void updateUser(User user) throws IOException;
}

• UserFeignControllerFailBack

@Component
public class UserFeignControllerFailBack implements UserFeignControllerClient {
    @Override
    public void addUser(User user) throws IOException {

    }

    @Override
    public User queryUserById(Integer id) {
        User user = new User("故障", false, "***", new Date(), "xxxx");
        user.setId(id);
        return user;
    }

    @Override
    public Map<String, Object> queryUserByPage(Integer pageNow, Integer pageSize, String column, String value) {
        return null;
    }

    @Override
    public void delteUserByIds(Integer[] ids) {

    }

    @Override
    public void updateUser(User user) throws IOException {

    }
}

Hystrix Dashboard

updateUser")
    @ResponseBody
    public void updateUser(User user) throws IOException;
}

• UserFeignControllerFailBack

@Component
public class UserFeignControllerFailBack implements UserFeignControllerClient {
    @Override
    public void addUser(User user) throws IOException {

    }

    @Override
    public User queryUserById(Integer id) {
        User user = new User("故障", false, "***", new Date(), "xxxx");
        user.setId(id);
        return user;
    }

    @Override
    public Map<String, Object> queryUserByPage(Integer pageNow, Integer pageSize, String column, String value) {
        return null;
    }

    @Override
    public void delteUserByIds(Integer[] ids) {

    }

    @Override
    public void updateUser(User user) throws IOException {

    }
}