spring cloud中声明式REST调用Feign
spring cloud中声明式REST调用Feign
文章目录
- spring cloud中声明式REST调用Feign
- 一、简介
- 二、步骤
- 2.1 Feign使用步骤
- 2.2 添加熔断步骤
- 三、示例
- 3.1 注册中心
- 3.1.1 maven依赖
- 3.1.2 application.yaml配置
- 3.1.3 启动类
- 3.2 服务
- 3.2.1 maven依赖
- 3.2.2 application.yaml配置
- 3.2.3 服务相关类
- 3.3 客户端
- 3.3.1 maven依赖
- 3.3.2 application.yaml配置
- 3.3.3 调用相关类
- 4.4 测试
一、简介
Feign是Netflix开发的声明式、模板化http客户端，简化了对http的调用。同时Feign带有负载均衡策略及熔断策略，这里对其使用进行介绍。
二、步骤
2.1 Feign使用步骤
开启Feign步骤如下：
-
添加核心maven依赖：
<dependency> <groupId>org.springframework.cloudgroupId> <artifactId>spring-cloud-starter-openfeignartifactId> dependency> -
启动类添加支持feign的注解@EnableFeignClients；
-
添加调用接口，并用注解@FeignClient修饰，注解内value值指定调用的服务名；
-
在上一步调用接口中，添加调用服务方法，用注解@RequestMapping修饰，注解内指定服务路径。服务方法参数用@RequestParam修饰；
-
在实用中，直接使用调用接口方法即可；
这里就完成了基本的feign使用步骤。
2.2 添加熔断步骤
熔断即当服务不可用时，提供的服务策略，在完成2.1中的所有步骤后，开启熔断还需步骤如下：
-
application.yaml中添加开启熔断配置：
feign: hystrix: enabled: true #feign添加支持熔断处理 -
添加熔断服务，即添加实现类，实现调用接口；
-
调用接口注解@FeignClient中属性fallback指定熔断服务类实例；
三、示例
这里使用注册中心spring_cloud_register_center、服务spring_cloud_provider、客户端spring_cloud_client_feign进行示例。
3.1 注册中心
注册中心为spring_cloud_register_center项目。
3.1.1 maven依赖
<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>4.0.0modelVersion>
<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.3.2.RELEASEversion>
<relativePath/>
parent>
<groupId>com.dragon.studygroupId>
<artifactId>spring_cloud_register_centerartifactId>
<version>0.0.1-SNAPSHOTversion>
<name>spring_cloud_register_centername>
<description>Demo project for Spring Bootdescription>
<properties>
<java.version>1.8java.version>
<spring-cloud.version>Hoxton.SR6spring-cloud.version>
properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-netflix-eureka-serverartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-testartifactId>
<scope>testscope>
dependency>
dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-dependenciesartifactId>
<version>${spring-cloud.version}version>
<type>pomtype>
<scope>importscope>
dependency>
dependencies>
dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-maven-pluginartifactId>
plugin>
plugins>
build>
project>
3.1.2 application.yaml配置
server:
port: 8010
spring:
application:
name: spring-cloud-register-center
eureka:
client:
serviceUrl:
defaultZone: http://localhost:${server.port}/eureka/
fetchRegistry: false #是否拉取注册信息，由于注册中心是单个结点，不需要拉取
registerWithEureka: false #是否注册自己，由于当前就是注册中心，帮不需要注册
3.1.3 启动类
package com.dragon.study.spring_cloud_register_center;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
@SpringBootApplication
@EnableEurekaServer
public class SpringCloudRegisterCenterApplication {
public static void main(String[] args) {
SpringApplication.run(SpringCloudRegisterCenterApplication.class, args);
}
}
3.2 服务
服务为spring_cloud_provider项目。
3.2.1 maven依赖
<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>4.0.0modelVersion>
<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.3.2.RELEASEversion>
<relativePath/>
parent>
<groupId>com.dragon.studygroupId>
<artifactId>spring_cloud_providerartifactId>
<version>0.0.1-SNAPSHOTversion>
<name>spring_cloud_providername>
<description>Demo project for Spring Bootdescription>
<properties>
<java.version>1.8java.version>
<spring-cloud.version>Hoxton.SR6spring-cloud.version>
properties>
<dependencies>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-webartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-testartifactId>
<scope>testscope>
dependency>
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<version>1.18.6version>
<scope>compilescope>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
dependency>
dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-dependenciesartifactId>
<version>${spring-cloud.version}version>
<type>pomtype>
<scope>importscope>
dependency>
dependencies>
dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-maven-pluginartifactId>
plugin>
plugins>
build>
project>
3.2.2 application.yaml配置
server:
port: 8011
spring:
application:
name: spring-cloud-provider
eureka:
instance:
prefer-ip-address: true #true表示使用ip注册，若为false，则表示使用系统hostname注册
client:
service-url:
default-zone: http://localhost:8010/eureka/
management:
endpoints:
web:
exposure:
include: "*"
3.2.3 服务相关类
定义实体bean类Stu.java
package com.dragon.study.spring_cloud_provider.bean;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Stu {
private String stuId;
private Integer age;
}
定义服务controller类StuController.java
package com.dragon.study.spring_cloud_provider.controller;
import com.dragon.study.spring_cloud_provider.bean.Stu;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("stu")
public class StuController {
@RequestMapping("getStu")
private Object getStu(Stu stu) {
System.out.println(stu);
return stu;
}
}
定义启动类SpringCloudProviderApplication.java
package com.dragon.study.spring_cloud_provider;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@SpringBootApplication
@EnableDiscoveryClient
public class SpringCloudProviderApplication {
public static void main(String[] args) {
SpringApplication.run(SpringCloudProviderApplication.class, args);
}
}
3.3 客户端
3.3.1 maven依赖
<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>4.0.0modelVersion>
<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.3.2.RELEASEversion>
<relativePath/>
parent>
<groupId>com.dragon.studygroupId>
<artifactId>spring_cloud_client_feignartifactId>
<version>0.0.1-SNAPSHOTversion>
<name>spring_cloud_client_feignname>
<description>Demo project for Spring Bootdescription>
<properties>
<java.version>1.8java.version>
<spring-cloud.version>Hoxton.SR6spring-cloud.version>
properties>
<dependencies>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-webartifactId>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-openfeignartifactId>
dependency>
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<optional>trueoptional>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-testartifactId>
<scope>testscope>
dependency>
dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-dependenciesartifactId>
<version>${spring-cloud.version}version>
<type>pomtype>
<scope>importscope>
dependency>
dependencies>
dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-maven-pluginartifactId>
plugin>
plugins>
build>
project>
3.3.2 application.yaml配置
server:
port: 8052
spring:
application:
name: spring-cloud-feign-client
eureka:
instance:
preferIpAddress: true #true表示使用ip注册，若为false，则表示使用系统hostname注册
client:
serviceUrl:
defaultZone: http://localhost:8010/eureka/
feign:
hystrix:
enabled: true #feign添加支持熔断处理
3.3.3 调用相关类
- 定义实体类：
package com.dragon.study.spring_cloud_feign_client.bean;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Stu {
private String stuId;
private Integer age;
}
- 定义启动类：
package com.dragon.study.spring_cloud_feign_client;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class SpringCloudFeignClientApplication {
public static void main(String[] args) {
SpringApplication.run(SpringCloudFeignClientApplication.class, args);
}
}
- 定义调用接口：
package com.dragon.study.spring_cloud_feign_client.service;
import com.dragon.study.spring_cloud_feign_client.bean.Stu;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
@FeignClient(value = "spring-cloud-provider", fallback = StuServiceHystrix.class)
public interface StuServiceFeign {
@RequestMapping("/stu/getStu")
Stu getStu(@RequestParam String stuId, @RequestParam Integer age);
}
- 定义熔断服务实现类：
package com.dragon.study.spring_cloud_feign_client.service;
import com.dragon.study.spring_cloud_feign_client.bean.Stu;
import org.springframework.stereotype.Service;
@Service
public class StuServiceHystrix implements StuServiceFeign {
//远程服务不可用时调用此实现
@Override
public Stu getStu(String stuId, Integer age) {
return new Stu("000",18);
}
}
- 定义controller:
package com.dragon.study.spring_cloud_feign_client.controller;
import com.dragon.study.spring_cloud_feign_client.bean.Stu;
import com.dragon.study.spring_cloud_feign_client.service.StuServiceFeign;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.annotation.Resource;
@RestController
@RequestMapping("stu")
public class StuController {
@Resource
private StuServiceFeign stuServiceFeign;
@RequestMapping("getStu")
public Object getStu(Stu stu) {
return stuServiceFeign.getStu(stu.getStuId(), stu.getAge());
}
}
4.4 测试
依次启动注册中心spring_cloud_register_center、服务spring_cloud_provider(启动多个实例，端口不同，服务名一样)、客户端spring_cloud_client_feign。
常规测试：
#在客户端多次调用服务，可获取正常结果，且服务端多个实例均有调用
GET http://localhost:8052/stu/getStu?stuId=001&age=17
Accept: application/json
上面正常输出如下：
{
"stuId": "001",
"age": 17
}
熔断测试，停掉所有服务，再次调次，输出为：
{
"stuId": "000",
"age": 18
}