【SpringCloud】Re03 Feign

Feign是一个声明式的HttpClient？更简洁的实现Http请求发送

安装Feign组件：

配置Feign的依赖坐标：

<?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>cloud-demo</artifactId>
        <groupId>cn.itcast.demo</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>order-service</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
        <!--eureka客户端依赖-->
        <!--<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>-->
        <!-- nacos客户端依赖包 -->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <!--feign客户端依赖-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!--引入HttpClient依赖-->
        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>
        <!--引入feign的统一api-->
        <dependency>
            <groupId>cn.itcast.demo</groupId>
            <artifactId>feign-api</artifactId>
            <version>1.0</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>app</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

启动类注册Feign

package cn.itcast.order;

import cn.itcast.feign.clients.UserClient;
import cn.itcast.feign.config.DefaultFeignConfiguration;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@MapperScan("cn.itcast.order.mapper")
@SpringBootApplication
@EnableFeignClients(clients = UserClient.class,defaultConfiguration = DefaultFeignConfiguration.class)
public class OrderApplication {

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

    /**
     * 创建RestTemplate并注入Spring容器
     */
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

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

编写Feign客户端接口？

package cn.itcast.feign.clients;

import cn.itcast.feign.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient(value = "userservice")
public interface UserClient {

    @GetMapping("/user/{id}")
    User findById(@PathVariable("id") Long id);
}

Feign的内部已经集成了Ribbon，使用方法不变

全局配置方式

server:
  port: 8088
spring:
  datasource:
    url: jdbc:mysql://mysql:3308/cloud_order?useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver
  application:
    name: orderservice
  cloud:
    nacos:
      server-addr: nacos:8848 # nacos服务地址
#      discovery:
#        namespace: 4d6ce343-9e1b-44df-a90f-2cf2b6b3d177 # dev环境
#        ephemeral: false # 是否是临时实例
mybatis:
  type-aliases-package: cn.itcast.user.pojo
  configuration:
    map-underscore-to-camel-case: true
logging:
  level:
    cn.itcast: debug
  pattern:
    dateformat: MM-dd HH:mm:ss:SSS
#eureka:
#  client:
#    service-url:  # eureka的地址信息
#      defaultZone: http://127.0.0.1:10086/eureka
userservice:
  ribbon:
    NFLoadBalancerRuleClassName: com.alibaba.cloud.nacos.ribbon.NacosRule  # 负载均衡规则
ribbon:
  eager-load:
    enabled: true # 开启饥饿加载
    clients: # 指定饥饿加载的服务名称
      - userservice
feign:
  httpclient:
    enabled: true # 支持HttpClient的开关
    max-connections: 200 # 最大连接数
    max-connections-per-route: 50 # 单个路径的最大连接数
  client:
    config:
      default: # default 表示全局生效 | 局部生效 指定服务名称 userservice 针对某一个服务进行配置
        loggerLevel: FULL

局部配置方式

  client:
    config:
      服务名: # default 表示全局生效 | 局部生效 指定服务名称 userservice 针对某一个服务进行配置
        loggerLevel: FULL

Java代码配置方式：

package cn.itcast.feign.config;

import feign.Logger;
import org.springframework.context.annotation.Bean;

public class DefaultFeignConfiguration {
    @Bean
    public Logger.Level logLevel(){
        return Logger.Level.BASIC;
    }
}

全局配置位置在启动类上注解：

package cn.itcast.order;

import cn.itcast.feign.clients.UserClient;
import cn.itcast.feign.config.DefaultFeignConfiguration;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@MapperScan("cn.itcast.order.mapper")
@SpringBootApplication
@EnableFeignClients(clients = UserClient.class,defaultConfiguration = DefaultFeignConfiguration.class)
public class OrderApplication {

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

    /**
     * 创建RestTemplate并注入Spring容器
     */
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

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

局部单个服务在Feign定义的服务接口上配置：

package cn.itcast.feign.clients;

import cn.itcast.feign.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.cloud.openfeign.FeignClientProperties;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient(value = "userservice", configuration = FeignClientProperties.FeignClientConfiguration.class)
public interface UserClient {

    @GetMapping("/user/{id}")
    User findById(@PathVariable("id") Long id);
}

Feign性能调整：

引入Feign的HttpClient依赖：

<?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>cloud-demo</artifactId>
        <groupId>cn.itcast.demo</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>order-service</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
        <!--eureka客户端依赖-->
        <!--<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>-->
        <!-- nacos客户端依赖包 -->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <!--feign客户端依赖-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!--引入HttpClient依赖-->
        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>
        <!--引入feign的统一api-->
        <dependency>
            <groupId>cn.itcast.demo</groupId>
            <artifactId>feign-api</artifactId>
            <version>1.0</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>app</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Feign的连接池配置：

server:
  port: 8088
spring:
  datasource:
    url: jdbc:mysql://mysql:3308/cloud_order?useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver
  application:
    name: orderservice
  cloud:
    nacos:
      server-addr: nacos:8848 # nacos服务地址
#      discovery:
#        namespace: 4d6ce343-9e1b-44df-a90f-2cf2b6b3d177 # dev环境
#        ephemeral: false # 是否是临时实例
mybatis:
  type-aliases-package: cn.itcast.user.pojo
  configuration:
    map-underscore-to-camel-case: true
logging:
  level:
    cn.itcast: debug
  pattern:
    dateformat: MM-dd HH:mm:ss:SSS
#eureka:
#  client:
#    service-url:  # eureka的地址信息
#      defaultZone: http://127.0.0.1:10086/eureka
userservice:
  ribbon:
    NFLoadBalancerRuleClassName: com.alibaba.cloud.nacos.ribbon.NacosRule  # 负载均衡规则
ribbon:
  eager-load:
    enabled: true # 开启饥饿加载
    clients: # 指定饥饿加载的服务名称
      - userservice
feign:
  httpclient:
    enabled: true # 支持HttpClient的开关
    max-connections: 200 # 最大连接数
    max-connections-per-route: 50 # 单个路径的最大连接数
#  client:
#    config:
#      default: # default 表示全局生效 | 局部生效 指定服务名称 userservice 针对某一个服务进行配置
#        loggerLevel: FULL

Feign的最佳使用方式

使用接口来共同约束编写规范

官方不推荐这种方式，紧耦合，约束过强，SpringMVC支持其他Http对象入参，被约束后将不适用

好处就是没有规范争议，闭着眼睛只管实现就完了

方式二：直接放在Common模块中，统一声明一系列配置，实体类，API接口

不管是哪个服务都统一从这里面进行资源调取

这个Feign-API POM信息：

<?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>cloud-demo</artifactId>
        <groupId>cn.itcast.demo</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>feign-api</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
    </dependencies>
</project>

User实体类：

package cn.itcast.feign.pojo;

import lombok.Data;

@Data
public class User {
    private Long id;
    private String username;
    private String address;
}

Feign的日志配置：

package cn.itcast.feign.config;

import feign.Logger;
import org.springframework.context.annotation.Bean;

public class DefaultFeignConfiguration {
    @Bean
    public Logger.Level logLevel(){
        return Logger.Level.BASIC;
    }
}

Feign接口：

package cn.itcast.feign.clients;

import cn.itcast.feign.pojo.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.cloud.openfeign.FeignClientProperties;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient(value = "userservice", configuration = FeignClientProperties.FeignClientConfiguration.class)
public interface UserClient {

    @GetMapping("/user/{id}")
    User findById(@PathVariable("id") Long id);
}

其他服务安装Feign-API，从Feign-API里面获取即可：

<?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>cloud-demo</artifactId>
        <groupId>cn.itcast.demo</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>order-service</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
        <!--eureka客户端依赖-->
        <!--<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>-->
        <!-- nacos客户端依赖包 -->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <!--feign客户端依赖-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!--引入HttpClient依赖-->
        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>
        <!--引入feign的统一api-->
        <dependency>
            <groupId>cn.itcast.demo</groupId>
            <artifactId>feign-api</artifactId>
            <version>1.0</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>app</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>