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[转][SpringCloud学习] 第三篇: 服务消费者(Fe

[转][SpringCloud学习] 第三篇: 服务消费者(Fe

作者: H_Man | 来源:发表于2017-07-27 17:33 被阅读17次

    转载自
    http://blog.csdn.net/forezp/article/details/69808079

    上一篇文章,讲述了通过restTemplate+ribbon去消费服务,这篇文章主要讲述通过feign去消费服务。

    一、Feign简介

    Feign是一个声明式的web服务客户端,它使得写web服务变得更简单。使用Feign,只需要创建一个接口并注解。它具有可插拔的注解特性,包括Feign 注解和JAX-RS注解。Feign同时支持可插拔的编码器和解码器。spring cloud对Spring mvc添加了支持,同时在spring web中次用相同的HttpMessageConverter。当我们使用feign的时候,spring cloud 整和了Ribbon和eureka去提供负载均衡。

    简而言之:

    • feign采用的是接口加注解
    • feign 整合了ribbon

    二、准备工作

    继续用上一节的工程: 启动eureka-server,端口为8761; 启动service-hi 两次,端口分别为8762 、8773.

    三、创建一个feign的服务

    创建一个spring-boot工程,取名为:serice-feign,它的pom文件为:

    <?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.forezp</groupId>
        <artifactId>service-feign</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <name>service-feign</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.2.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>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-eureka</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-feign</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>Dalston.RC1</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>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>
    
    
    </project>
    

    向服务注册中心注册它自己,这时service-feign既是服务提供者,也是服务消费者,配置文件application.yml

    eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:8761/eureka/
    server:
      port: 8765
    spring:
      application:
        name: service-feign
    

    在程序的入口类,需要通过注解@EnableFeignClients来开启feign:

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

    定义一个feign接口类,通过@ FeignClient(“服务名”),来指定调用哪个服务:

    @FeignClient(value = "service-hi")
    public interface SchedualServiceHi {
        @RequestMapping(value = "/hi",method = RequestMethod.GET)
        String sayHiFromClientOne(@RequestParam(value = "name") String name);
    }
    

    在web层的controllrt:

    @RestController
    public class HiController {
    
        @Autowired
        SchedualServiceHi schedualServiceHi;
        @RequestMapping(value = "/hi",method = RequestMethod.GET)
        public String sayHi(@RequestParam String name){
            return schedualServiceHi.sayHiFromClientOne(name);
        }
    }
    
    

    访问http://localhost:8765/hi?name=forezp,浏览器交替显示:

    hi forezp,i am from port:8762
    
    hi forezp,i am from port:8763
    

    四、更改feign的配置

    在声明feignclient的时候,不仅要指定服务名,同时需要制定服务配置类:

    @FeignClient(name = "stores", configuration = FooConfiguration.class)
    public interface StoreClient {
        //..
    }
    

    重写配置,需要加@Configuration注解,并重写下面的两个bean,栗子:

    @Configuration
    public class FooConfiguration {
        @Bean
        public Contract feignContractg() {
            return new feign.Contract.Default();
        }
    
        @Bean
        public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
            return new BasicAuthRequestInterceptor("user", "password");
        }
    }
    

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