《Feign 声明式客户端接口》

微服务应用中，ribbon 和 hystrix 总是同时出现，feign 整合了两者，并提供了声明式消费者客户端

注意 ：

• 用 feign 代替 hystrix+ribbon

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Feign 声明式客户端接口

新建 sp09-feign 项目

创建项目

添加依赖

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pom.xml (依赖文件)

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>cn.tedu</groupId>
    <artifactId>sp09-feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>sp09-feign</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <spring-boot.version>2.3.7.RELEASE</spring-boot.version>
        <spring-cloud.version>Hoxton.SR9</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web-services</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>
<!--    公共模块    -->
        <dependency>
            <groupId>cn.tedu</groupId>
            <artifactId>sp01-commons</artifactId>
            <version>1.0-SNAPSHOT</version>
        </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>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.3.7.RELEASE</version>
                <configuration>
                    <mainClass>cn.tedu.sp09.Sp09FeignApplication</mainClass>
                </configuration>
                <executions>
                    <execution>
                        <id>repackage</id>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

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application.yml （配置文件）

spring:
  application:
    name: feign
    
server:
  port: 3001
  
eureka:
  client:
    service-url:
      defaultZone: http://eureka1:2001/eureka, http://eureka2:2002/eureka

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主程序添加 @EnableDiscoveryClient 和 @EnableFeignClients

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class Sp09FeignApplication {
    
    

	public static void main(String[] args) {
    
    
		SpringApplication.run(Sp09FeignApplication.class, args);
	}

}

java 源文件

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Feign 声明式客户端

Feign 利用了我们熟悉的 spring mvc 注解来对接口方法进行设置，降低了我们的学习成本。

通过这些设置，Feign可以拼接后台服务的，访问路径和提交的参数

例如：

@GetMapping("/{userId}/score") 
JsonResult addScore(@PathVariable Integer userId, @RequestParam Integer score);

当这样调用该方法：

service.addScore(7, 100);

那么 feign 会向服务器发送请求：

http://用户微服务/7/score?score=100

• 注意：如果 score 参数名与变量名不同，需要添加参数名设置：

@GetMapping("/{userId}/score") 
JsonResult addScore(@PathVariable Integer userId, @RequestParam("score") Integer s);

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service定义接口

定义service接口 相当于我们业务服务器的 service ，用来远程调用

ItemClient (service接口)

@FeignClient(name="item-service")
public interface ItemClient {
    
    
    @GetMapping("/{orderId}")
    JsonResult<List<Item>> getItems(@PathVariable("orderId")  String orderId);

    @PostMapping("/decreaseNumber")
    JsonResult<?> decreaseNumber(@RequestBody List<Item> items);
}

UserClient (service接口)

@FeignClient(name = "user-service")
public interface UserClient {
    
    
    @GetMapping("/{userId}")
    JsonResult<User> getUser(@PathVariable("userId") Integer userId);

    @GetMapping("/{UserId}/score")
    JsonResult<?> addScore(@PathVariable("userId") Integer userId,@RequestParam("score") Integer score);
}

OrderClient (service接口)

@FeignClient(name = "order-service")
public interface OrderClient {
    
    
    @GetMapping("/{orderId}")
    JsonResult<Order> getOrder(@PathVariable("orderId") String orderId);

    @GetMapping("/")
    JsonResult<?> saveOrder();
}

@FeignClient(name="业务服务器名") —— 远程调用，调用的是item-service业务服务器

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Controller(控制层)

@RestController
@Slf4j
public class feignController {
    
    
    @Autowired
    private ItemClient itemClient;
    @Autowired
    private OrderClient orderClient;
    @Autowired
    private UserClient userClient;

    @GetMapping("/item-service/{orderId}")
    public JsonResult<List<Item>> getItems(@PathVariable() String orderId){
    
    
        return itemClient.getItems(orderId);
    }

    @PostMapping("/item-service/decreaseNumber")
    public JsonResult<?> decreaseNumber(@RequestBody List<Item> items){
    
    
        return  itemClient.decreaseNumber(items);
    }

    @GetMapping("/user-service/{userId}")
    public JsonResult<User> getUser(@PathVariable("userId") Integer userId){
    
    
        return userClient.getUser(userId);
    }
    @GetMapping("/user-service/{userId}/score")
    public JsonResult<?> addSocre(@PathVariable("userId") Integer userId,Integer score){
    
    
        return userClient.addScore(userId,score);
    }
    @GetMapping("/order-service/{orderId}")
    public JsonResult<Order> getOrder(@PathVariable("orderId") String orderId){
    
    
        return orderClient.getOrder(orderId);
    }
    @GetMapping("/order-service")
    public JsonResult<?> getOrder(){
    
    
        return orderClient.saveOrder();
    }

}

调用流程

启动服务，并访问测试

http://localhost:3001/item-service/decreaseNumber

查看eureka 是否注册到

http://localhost:3001/item-service/decreaseNumber
测试 item-service