Spring Cloud Hystrix服務降級

搭建三個工程eureka-server，hello-service，hystrix-service。

eureka-server搭建，pom.xml文件如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.2.8.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.hangzhou.springcloud</groupId>
	<artifactId>eureka-server</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>eureka-server</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
		<spring-cloud.version>Hoxton.SR6</spring-cloud.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
	</dependencies>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>${spring-cloud.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

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

</project>

application.properties文件如下：

# 指定運行端口號
server.port=1111
 
# 指定服務名稱
spring.applcation.name=eureka-server
# 指定本機地址
eureka.instance.hostname=localhost
# 指定是否將服務註冊到註冊中心（註冊中心不需要開啓）
eureka.client.register-with-eureka=false
# 指定是否從註冊中心獲取服務(註冊中心不需要開啓)
eureka.client.fetch-registry=false

程序啓動類，編寫如下：

@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApplication {

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

}

自此註冊中心搭建完畢。

hello-service搭建開始，pom.xml文件如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.2.8.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.hangzhou.springcloud</groupId>
	<artifactId>hello-service</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>hello-service</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
		<spring-cloud.version>Hoxton.SR6</spring-cloud.version>
	</properties>

	<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-eureka-client</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
	</dependencies>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>${spring-cloud.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

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

</project>

application.properties文件如下：

# 指定運行端口號
server.port=1112
 
# 指定服務名稱
spring.application.name=hello-service
# 指定本機地址
eureka.instance.hostname=localhost
# 指定是否將服務註冊到註冊中心（註冊中心不需要開啓）
eureka.client.register-with-eureka=true
# 指定是否從註冊中心獲取服務(註冊中心不需要開啓)
eureka.client.fetch-registry=true
# 配置註冊中心地址
eureka.client.service-url.defaultZone=http://localhost:1111/eureka

程序啓動類，如下所示：

@EnableDiscoveryClient
@SpringBootApplication
public class HelloServiceApplication {

	public static void main(String[] args) {
		SpringApplication.run(HelloServiceApplication.class, args);
	}

}

controller類中，加入睡眠方便實現服務降級效果。

@RequestMapping("/test")
@RestController
public class HelloController {
	@GetMapping(value="/hello")
	public String hello() throws InterruptedException {
		System.out.println("進入helloword");
		new Thread().sleep(5000);
		return "hello word";
	}
}

自此服務提供者搭建完畢，下面我們來搭建hystrix.service，pom.xml文件如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.2.8.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.hangzhou.springcloud</groupId>
	<artifactId>hystrix-service</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>hystrix-service</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
		<spring-cloud.version>Hoxton.SR6</spring-cloud.version>
	</properties>

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

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
	</dependencies>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>${spring-cloud.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

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

</project>

application.properties文件如下：

# 指定運行端口號
server.port=1116
# 服務名稱
spring.application.name=hystrix-service

eureka.client.fetch-registry=true
eureka.client.register-with-eureka=true
eureka.client.service-url.defaultZone=http://localhost:1111/eureka/

程序啓動類代碼如下：

@EnableCircuitBreaker
@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class HystrixServiceApplication {

	public static void main(String[] args) {
		SpringApplication.run(HystrixServiceApplication.class, args);
	}

}

feign客戶端調用工具如下：

//此value值與服務提供者的spring.application.name的值是一致的
@FeignClient(value = "hello-service")
public interface HelloService {
	//服務提供者的全路徑訪問(不包括http://localhost:1112)
	@GetMapping(value="/test/hello")
	public String hello();
		
	
}

controller類如下所示：

@RestController
@RequestMapping("/hystrix")
public class HystrixController {
	
	@Autowired
	private HelloService helloService;
	
	@RequestMapping("/hello")
	@HystrixCommand(fallbackMethod = "testHello")
	public String hello() {
		return helloService.hello();
	}
	
	public String testHello() {
		return "服務調用不通過,服務降級";
	}
}

搭建完畢，依次啓動項目eureka-server，hello-servic，hystrix-service目錄，遊覽器輸入http://localhost:1116/hystrix/hello,效果如下圖所示：