SpringCloud中Feign的简介及基础使用_springclound feign-优快云博客

概念

Feign简介
　　Feign是Netflix开发的声明式、模板化的HTTP客户端，其灵感来自Retrofit、JAXRS-2.0以及WebSocket。Feign可帮助我们更加便捷、优雅地调用HTTP API。
　　在Spring Cloud中，使用Feign非常简单——创建一个接口，并在接口上添加一些注解，代码就完成了。Feign支持多种注解，例如Feign自带的注解或者
　　JAX-RS注解等。
　　Spring Cloud对Feign进行了增强，使Feign支持了Spring MVC注解，并整合了Ribbon和Eureka，从而让Feign的使用更加方便。

创建工程

具体实现

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>com.itmuch.cloud</groupId>
  <artifactId>microservice-consumer-movie-feign</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <!-- 引入spring boot的依赖 -->
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.3.RELEASE</version>
  </parent>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>1.8</java.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>

    <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>
  </dependencies>

  <!-- 引入spring cloud的依赖 -->
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>Camden.SR4</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

  <!-- 添加spring-boot的maven插件 -->
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>

application.yml

server:
  port: 8010
spring:
  application:
    name: microservice-consumer-movie
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
  instance:
    prefer-ip-address: true

User

package com.itmuch.cloud.study.user.entity;

import java.math.BigDecimal;

public class User {
  private Long id;
  private String username;
  private String name;
  private Integer age;
  private BigDecimal balance;

  public Long getId() {
    return this.id;
  }

  public void setId(Long id) {
    this.id = id;
  }

  public String getUsername() {
    return this.username;
  }

  public void setUsername(String username) {
    this.username = username;
  }

  public String getName() {
    return this.name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Integer getAge() {
    return this.age;
  }

  public void setAge(Integer age) {
    this.age = age;
  }

  public BigDecimal getBalance() {
    return this.balance;
  }

  public void setBalance(BigDecimal balance) {
    this.balance = balance;
  }
}

UserFeignClient

package com.itmuch.cloud.study.user.feign;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.itmuch.cloud.study.user.entity.User;

@FeignClient(name = "microservice-provider-user")
public interface UserFeignClient {
  @RequestMapping(value = "/{id}", method = RequestMethod.GET)
  public User findById(@PathVariable("id") Long id);
}

说明：

    1）创建一个Feign接口，并添加@FeignClient注解；
    2）在这里，我们避免了硬编码，直接用@FeignClient注解，将用户微服务名称进行绑定。@FeignClient注解中的microservice-provider-user是一个任意的客户端名称，用于创建Ribbon负载均衡器。在本例中，由于使用了Eureka，所以Ribbon会把microservice-provider-user解析成Eureka Server服务注册表中的服务。
    如果不想使用Eureka，也可使用service.ribbon.listOfServers属性配置服务器列表也可使用url属性指定请求的URL（URL可以是完整的URL或主机名），例如@FeignClient(name = "microservice-provider-user", url = "http://localhost:8000/")；
    3）而且这里在@FeignClient注解下，只能用@RequestMapping注解而不能用@GetMapping，且获取参数必须写完整@PathVariable("id")；

MovieController

package com.itmuch.cloud.study.user.controller;

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.RestController;

import com.itmuch.cloud.study.user.entity.User;
import com.itmuch.cloud.study.user.feign.UserFeignClient;

@RestController
public class MovieController {
  @Autowired
  private UserFeignClient userFeignClient;

  @GetMapping("/user/{id}")
  public User findById(@PathVariable Long id) {
    return this.userFeignClient.findById(id);
  }
}

ConsumerMovieApplication

package com.itmuch.cloud.study;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

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

说明：

1）添加@EnableFeignClients注解；