Hystrix是Netflix的Library。 Hystrix隔离服务之间的访问点,停止服务之间的级联故障,并提供后备选项。
首先,无涯教程需要在构建配置文件中添加Spring Cloud Starter Hystrix依赖项。
Maven用户可以在pom.xml文件中添加以下依赖项-
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-hystrix</artifactId> </dependency>
Gradle用户可以在build.gradle文件中添加以下依赖项-
compile('org.springframework.cloud:spring-cloud-starter-hystrix')
现在,将@EnableHystrix批注添加到主Spring Boot应用程序类文件中。 @EnableHystrix批注用于将Hystrix功能启用到您的Spring Boot应用程序中。
下面给出了主要的Spring Boot应用程序类文件代码-
package com.learnfk.hystrixapp; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.hystrix.EnableHystrix; @SpringBootApplication @EnableHystrix public class HystrixappApplication { public static void main(String[] args) { SpringApplication.run(HystrixappApplication.class, args); } }
现在编写一个简单的Rest Controller,以便它在请求的时间后3秒钟后返回String。
@RequestMapping(value="/") public String hello() throws InterruptedException { Thread.sleep(3000); return "Welcome Hystrix"; }
现在,为Rest API添加@Hystrix命令和@HystrixProperty并定义以毫秒为单位的超时值。
@HystrixCommand(fallbackMethod="fallback_hello", commandProperties={ @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds", value="1000") })
接下来,如果请求需要很长时间才能响应,则定义回退方法fallback_hello()。
private String fallback_hello() { return "Request fails. It takes long time to response"; }
此处显示了包含REST API和Hystrix属性的完整Rest Controller类文件-
@RequestMapping(value="/") @HystrixCommand(fallbackMethod="fallback_hello", commandProperties={ @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds", value="1000") }) public String hello() throws InterruptedException { Thread.sleep(3000); return "Welcome Hystrix"; } private String fallback_hello() { return "Request fails. It takes long time to response"; }
在此示例中,REST API编写在主Spring Boot应用程序类文件本身中。
package com.learnfk.hystrixapp; import org.springframework.boot.SpringApplication; import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.hystrix.EnableHystrix; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand; @SpringBootApplication @EnableHystrix @RestController public class HystrixappApplication { public static void main(String[] args) { SpringApplication.run(HystrixappApplication.class, args); } @RequestMapping(value="/") @HystrixCommand(fallbackMethod="fallback_hello", commandProperties={ @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds", value="1000") }) public String hello() throws InterruptedException { Thread.sleep(3000); return "Welcome Hystrix"; } private String fallback_hello() { return "Request fails. It takes long time to response"; } }
完整的构建配置文件如下所示。
Maven-pom.xml文件
<?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>com.learnfk</groupId> <artifactId>hystrixapp</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>hystrixapp</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.9.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> <spring-cloud.version>Edgware.RELEASE</spring-cloud.version> </properties> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-hystrix</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>${spring-cloud.version}</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
Gradle – build.gradle
buildscript { ext { springBootVersion='1.5.9.RELEASE' } repositories { mavenCentral() } dependencies { classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}") } } apply plugin: 'java' apply plugin: 'eclipse' apply plugin: 'org.springframework.boot' group='com.learnfk' version='0.0.1-SNAPSHOT' sourceCompatibility=1.8 repositories { mavenCentral() } ext { springCloudVersion='Edgware.RELEASE' } dependencies { compile('org.springframework.cloud:spring-cloud-starter-hystrix') compile('org.springframework.boot:spring-boot-starter-web') testCompile('org.springframework.boot:spring-boot-starter-test') } dependencyManagement { imports { mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}" } }
您可以创建一个可执行的JAR文件,并使用以下Maven或Gradle命令运行Spring Boot应用程序-
对于Maven,使用如下所示的命令-
mvn clean install
在" BUILD SUCCESS"之后,您可以在目标目录下找到JAR文件。
对于Gradle,使用如下所示的命令-
gradle clean build
在" BUILD SUCCESSFUL"之后,您可以在build/libs目录下找到JAR文件。
现在,使用下面给出的命令运行JAR文件:
java –jar <JARFILE>
这将在Tomcat端口8080上启动应用程序,如下所示-
现在,从Web浏览器中访问URL http:// localhost:8080/,然后查看Hystrix响应。该API需要3秒钟来响应,但是Hystrix超时是1秒。
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