(四)SpringCloud之Feign声明式服务调用

入门案例

1、创建Maven聚合项目

• Feign-Demo：父项目
• eureka-server：Eureka注册中心
• eureka-server02：Eureka注册中心
• service-provider：服务提供者
• service-consumer：服务消费者

父项目: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>

    <groupId>cn.yanghuisen</groupId>
    <artifactId>Feign-Demo</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>eureka-server</module>
        <module>service-provider</module>
        <module>service-consumer</module>
    </modules>

    <!-- 继承 spring-boot-starter-parent 依赖 -->
    <!-- 使用继承方式，实现复用，符合继承的都可以被使用 -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.0.RELEASE</version>
    </parent>

    <!--
        集中定义依赖组件版本号，但不引入，
        在子工程中用到声明的依赖时，可以不加依赖的版本号，
        这样可以统一管理工程中用到的依赖版本
     -->
    <properties>
        <!-- Spring Cloud Hoxton.SR5 依赖 -->
        <spring-cloud.version>Hoxton.SR5</spring-cloud.version>
    </properties>

    <!-- 项目依赖管理 父项目只是声明依赖，子项目需要写明需要的依赖(可以省略版本信息) -->
    <dependencyManagement>
        <dependencies>
            <!-- spring cloud 依赖 -->
            <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>


</project>

2、eureka注册中心

2.1、eureka-server

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">
    <parent>
        <artifactId>Feign-Demo</artifactId>
        <groupId>cn.yanghuisen</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>eureka-server</artifactId>

    <name>eureka-server</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <!-- 项目依赖 -->
    <dependencies>
        <!-- netflix eureka server 依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <!-- spring boot web 依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- spring boot test 依赖 -->
        <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>
</project>

application.yml

server:
  port: 8761 # 端口

spring:
  application:
    name: eureka-server # 应用名称(集群下相同)

# 配置 Eureka Server 注册中心
eureka:
  instance:
    hostname: eureka01            # 主机名，不配置的时候将根据操作系统的主机名来获取
    prefer-ip-address: true       # 是否使用 ip 地址注册
    instance-id: ${
    
    spring.cloud.client.ip-address}:${
    
    server.port} # ip:port
  client:
    # 设置服务注册中心地址，指向另一个注册中心
    service-url:                  # 注册中心对外暴露的注册地址
      defaultZone: http://localhost:8762/eureka/

启动类

package cn.yanghuisen;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
// 开启 EurekaServer 注解
@EnableEurekaServer
public class EurekaServerApplication {
    
    

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

}

2.2、eureka-server02

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">
    <parent>
        <artifactId>Feign-Demo</artifactId>
        <groupId>cn.yanghuisen</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>eureka-server02</artifactId>

    <name>eureka-server02</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <!-- 项目依赖 -->
    <dependencies>
        <!-- netflix eureka server 依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <!-- spring boot web 依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- spring boot test 依赖 -->
        <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>
</project>

application.yml

spring:
  application:
    name: eureka-server # 应用名称(集群下相同)

# 端口
server:
  port: 8762

# 配置 Eureka Server 注册中心
eureka:
  instance:
    hostname: eureka02            # 主机名，不配置的时候将根据操作系统的主机名来获取
    prefer-ip-address: true       # 是否使用 ip 地址注册
    instance-id: ${
    
    spring.cloud.client.ip-address}:${
    
    server.port} # ip:port
  client:
    # 设置服务注册中心地址，指向另一个注册中心
    service-url:                  # 注册中心对外暴露的注册地址
      defaultZone: http://localhost:8761/eureka/

启动类

package cn.yanghuisen;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
// 开启 EurekaServer 注解
@EnableEurekaServer
public class EurekaServer02Application {
    
    

    public static void main(String[] args) {
    
    
        SpringApplication.run(EurekaServer02Application.class, args);
    }

}

3、provider服务提供者

3.1、service-provider

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">
  <parent>
    <artifactId>Feign-Demo</artifactId>
    <groupId>cn.yanghuisen</groupId>
    <version>1.0-SNAPSHOT</version>
  </parent>
  <modelVersion>4.0.0</modelVersion>

  <artifactId>service-provider</artifactId>

  <name>service-provider</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>

  <!-- 项目依赖 -->
  <dependencies>
    <!-- netflix eureka client 依赖 -->
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
    <!-- spring boot web 依赖 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- lombok 依赖 -->
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <scope>provided</scope>
    </dependency>

    <!-- spring boot test 依赖 -->
    <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>
</project>

实体类

package cn.yanghuisen.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Product implements Serializable {
    
    

    private Integer id;
    private String productName;
    private Integer productNum;
    private Double productPrice;

}

服务类接口

package cn.yanghuisen.service;


import cn.yanghuisen.pojo.Product;

import java.util.List;

/**
 * 商品服务
 */
public interface ProductService {
    
    

    /**
     * 查询商品列表
     *
     * @return
     */
    List<Product> selectProductList();

}

服务类接口实现类

package cn.yanghuisen.service.impl;

import cn.yanghuisen.pojo.Product;
import cn.yanghuisen.service.ProductService;
import org.springframework.stereotype.Service;

import java.util.Arrays;
import java.util.List;

/**
 * 商品服务
 */
@Service
public class ProductServiceImpl implements ProductService {
    
    

    /**
     * 查询商品列表
     *
     * @return
     */
    @Override
    public List<Product> selectProductList() {
    
    
        return Arrays.asList(
                new Product(1, "华为手机", 1, 5800D),
                new Product(2, "联想笔记本", 1, 6888D),
                new Product(3, "小米平板", 5, 2020D)
        );
    }

}

控制层

package cn.yanghuisen.controller;

import cn.yanghuisen.pojo.Product;
import cn.yanghuisen.service.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/product")
public class ProductController {
    
    

    @Autowired
    private ProductService productService;

    /**
     * 查询商品列表
     *
     * @return
     */
    @GetMapping("/list")
    public List<Product> selectProductList() {
    
    
        return productService.selectProductList();
    }

}

启动类

package cn.yanghuisen;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
// 开启 EurekaClient 注解，目前版本如果配置了 Eureka 注册中心，默认会开启该注解
//@EnableEurekaClient
public class ServiceProviderApplication {
    
    

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

}

3.2、service-provider02

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">
    <parent>
        <artifactId>Feign-Demo</artifactId>
        <groupId>cn.yanghuisen</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>service-provider02</artifactId>

    <name>service-provider02</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <!-- 项目依赖 -->
    <dependencies>
        <!-- netflix eureka client 依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!-- spring boot web 依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- lombok 依赖 -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>

        <!-- spring boot test 依赖 -->
        <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>
</project>

实体类

package cn.yanghuisen.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Product implements Serializable {
    
    

    private Integer id;
    private String productName;
    private Integer productNum;
    private Double productPrice;

}

服务类接口

package cn.yanghuisen.service;


import cn.yanghuisen.pojo.Product;

import java.util.List;

/**
 * 商品服务
 */
public interface ProductService {
    
    

    /**
     * 查询商品列表
     *
     * @return
     */
    List<Product> selectProductList();

}

服务类接口实现类

package cn.yanghuisen.service.impl;

import cn.yanghuisen.pojo.Product;
import cn.yanghuisen.service.ProductService;
import org.springframework.stereotype.Service;

import java.util.Arrays;
import java.util.List;

/**
 * 商品服务
 */
@Service
public class ProductServiceImpl implements ProductService {
    
    

    /**
     * 查询商品列表
     *
     * @return
     */
    @Override
    public List<Product> selectProductList() {
    
    
        return Arrays.asList(
                new Product(1, "华为手机", 1, 5800D),
                new Product(2, "联想笔记本", 1, 6888D),
                new Product(3, "小米平板", 5, 2020D)
        );
    }

}

控制层

package cn.yanghuisen.controller;

import cn.yanghuisen.pojo.Product;
import cn.yanghuisen.service.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/product")
public class ProductController {
    
    

    @Autowired
    private ProductService productService;

    /**
     * 查询商品列表
     *
     * @return
     */
    @GetMapping("/list")
    public List<Product> selectProductList() {
    
    
        return productService.selectProductList();
    }

}

启动类

package cn.yanghuisen;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
// 开启 EurekaClient 注解，目前版本如果配置了 Eureka 注册中心，默认会开启该注解
//@EnableEurekaClient
public class ServiceProviderApplication {
    
    

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

}

4、consumer服务消费者

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">
    <parent>
        <artifactId>Feign-Demo</artifactId>
        <groupId>cn.yanghuisen</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>service-consumer</artifactId>

    <name>service-consumer</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <!-- 项目依赖 -->
    <dependencies>
        <!-- netflix eureka client 依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            <!--去除jackson-dataformat-xml，否则会返回xml文件，而不是JSON-->
            <exclusions>
                <exclusion>
                    <groupId>com.fasterxml.jackson.dataformat</groupId>
                    <artifactId>jackson-dataformat-xml</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <!-- spring cloud openfeign 依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!-- spring boot web 依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- lombok 依赖 -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>

        <!-- spring boot test 依赖 -->
        <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>
</project>

eureka中默认集成com.fasterxml.jackson.dataformat，用于返回xml格式的数据，但是由于xml的等级比JSON高，所以在要返回JSON的时候，将会被替换为XML，剔除com.fasterxml.jackson.dataformat后就可以正常返回JSON数据。

application.yml

server:
  port: 9090 # 端口

spring:
  application:
    name: service-consumer # 应用名称

# 配置 Eureka Server 注册中心
eureka:
  client:
    register-with-eureka: false         # 是否将自己注册到注册中心，默认为 true
    registry-fetch-interval-seconds: 10 # 表示 Eureka Client 间隔多久去服务器拉取注册信息，默认为 30 秒
    service-url:                        # 设置服务注册中心地址
      defaultZone: http://localhost:8761/eureka/,http://localhost:8762/eureka/

实体类

package cn.yanghuisen.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Product implements Serializable {
    
    

    private Integer id;
    private String productName;
    private Integer productNum;
    private Double productPrice;

}

package cn.yanghuisen.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.List;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Order implements Serializable {
    
    

    private Integer id;
    private String orderNo;
    private String orderAddress;
    private Double totalPrice;
    private List<Product> productList;

}

服务类接口

package cn.yanghuisen.service;

import cn.yanghuisen.pojo.Product;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

import java.util.List;

// 声明需要调用的服务
@FeignClient("service-provider")
public interface ProductService {
    
    

    /**
     * 查询商品列表
     *
     * @return
     */
    // 配置需要调用的服务地址及参数
    @GetMapping("/product/list")
    List<Product> selectProductList();

}

package cn.yanghuisen.service;


import cn.yanghuisen.pojo.Order;

public interface OrderService {
    
    

    /**
     * 根据主键查询订单
     *
     * @param id
     * @return
     */
    Order selectOrderById(Integer id);

}

服务接口实现类

package cn.yanghuisen.service.impl;

import cn.yanghuisen.pojo.Order;
import cn.yanghuisen.service.OrderService;
import cn.yanghuisen.service.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class OrderServiceImpl implements OrderService {
    
    

    @Autowired
    private ProductService productService;

    /**
     * 根据主键查询订单
     *
     * @param id
     * @return
     */
    @Override
    public Order selectOrderById(Integer id) {
    
    
        return new Order(id, "order-001", "中国", 22788D,
                productService.selectProductList());
    }

}

控制层

package cn.yanghuisen.controller;

import cn.yanghuisen.pojo.Order;
import cn.yanghuisen.service.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/order")
public class OrderController {
    
    

    @Autowired
    private OrderService orderService;

    /**
     * 根据主键查询订单
     *
     * @param id
     * @return
     */
    @GetMapping("/{id}")
    public Order selectOrderById(@PathVariable("id") Integer id) {
    
    
        return orderService.selectOrderById(id);
    }

}

启动类

package cn.yanghuisen;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
// 开启 EurekaClient 注解，目前版本如果配置了 Eureka 注册中心，默认会开启该注解
//@EnableEurekaClient
// 开启 FeignClients 注解
@EnableFeignClients
public class ServiceConsumerApplication {
    
    

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

}

启动项目，先启动两个注册中心，再启动两个服务提供者，最后启动服务消费者

访问：http://localhost:9090/order/1

负载均衡

1、全局

@Bean
public RandomRule randomRule() {
    
    
    return new RandomRule();
}

2、局部

# 负载均衡策略
# service-provider 为调用的服务的名称
service-provider:
  ribbon:
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule