SpringCloud的学习记录(6)

这一章节讲fegin的使用.

在我们生成的Demo项目上右键点击New->Module->spring Initializr, 然后next, 填写Group和Artifact等信息，

这里Artifact填写feginclient, 再次next, 选择内容如下的pom.xml:

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.xum</groupId>
    <artifactId>feign-client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>feign-client</name>
    <description>Demo project for Spring Boot</description>
 
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.RELEASE</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-openfeign</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-netflix-hystrix-dashboard</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</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>
 
    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>
 
</project>

fegin-client项目结构如下:

1. 首先FeginClientApplication.java里的内容如下:

package com.xum.feignclient;
 
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.ComponentScan;
 
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
@ComponentScan(basePackages = { "com.xum.feignclient.controller", "com.xum.feignclient.server" })
public class FeignClientApplication {
 
    public static void main(String[] args) {
        SpringApplication.run(FeignClientApplication.class, args);
    }
 
}

2. application.yml内容如下:

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8772
spring:
  application:
    name: fegin-client
feign:
  hystrix:
    enabled: true
management:
  endpoint:
    health:
      show-details: always
  endpoints:
    web:
      exposure:
        include: '*'

3. 然后FeignConsumerController.java内容如下:

package com.xum.feignclient.controller;
 
import com.xum.feignclient.server.HelloService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
@RequestMapping(value = "/feign")
public class FeignConsumerController {
 
    private static final Logger LOG = LoggerFactory.getLogger(FeignConsumerController.class);
 
    @Autowired
    HelloService helloService;
 
    @RequestMapping(value = "/feignconsumer")
    public String helloConsumer(){
        LOG.info("FeginConsumerController=>helloConsumer");
        return helloService.hello();
    }
 
    @RequestMapping(value = "/test")
    public String test() {
        return "test";
    }
}

4. 其次就是HelloService.java接口内容如下:

package com.xum.feignclient.server;
 
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;

// 这里的FeginClient注解, value是说明调用的那个项目,就是spring.application.name对应的名字; 

// fallback是调用value项目api失败后, 处理的方法类, 这也是自定义的.
@FeignClient(value = "eureka-client", fallback = HystrixService.class)
public interface HelloService {
 
    @RequestMapping(value = "/testone/test")
    String hello();
 
}

5. 然后是HystrixService.java内容如下:

package com.xum.feignclient.server;
 
import org.springframework.stereotype.Service;
 
@Service
public class HystrixService implements HelloService {
    // 这里就是当调用api失败后, 对应的处理方法.
    @Override
    public String hello() {
        return " HelloService=>HystrixService=>eureka-client is unable ...";
    }
 
}

现在启动如下的项目:

1. eureka-server

2. config-server

3. feign-client

4. eureka-client

在浏览器或则post man中输入api：http://localhost:8772/feign/feignconsumer, 显示内容如下:

说明成功调用eureka-client项目里的testone/test这条api.

现在把eureka-client项目停止, 然后再输入这条api: http://localhost:8772/feign/feignconsumer, 内容如下:

现在这里输出的是HystrixService.java里的内容里, 自我保护的机制.