10.0 Feign与注册中心
声明式远程调用
feign是一个声明式的HTTP客户端，他的目的就是让远程调用更加简单。
给远程服务发的是HTTP请求。
会员服务（member）调优惠券（coupon）服务
会员服务通过openFeign先去注册中心找优惠券服务
10.1 引入 openfeign 依赖
会员服务想要远程调用优惠券服务，只需要给会员服务里引入openfeign依赖，他就有了远程调用其他服务的能力。
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
10.2 在coupon服务(被调用服务)中修改如下的内容
@RequestMapping("coupon/coupon")
public class CouponController {
@Autowired
private CouponService couponService;
@RequestMapping("/member/list")
public R membercoupons(){ //全系统的所有返回都返回R
// 应该去数据库查用户对于的优惠券，但这个我们简化了，不去数据库查了，构造了一个优惠券给他返回
CouponEntity couponEntity = new CouponEntity();
couponEntity.setCouponName("满100减10");//优惠券的名字
return R.ok().put("coupons",Arrays.asList(couponEntity));
}
在member的配置类上加注解@EnableFeignClients(basePackages="com.yxj.gulimall.member.feign")，
告诉spring这里面是一个远程调用客户端，member要调用的接口
package com.yxj.gulimall.member;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication
@MapperScan("com.yxj.gulimall.member.dao")
@EnableDiscoveryClient
@EnableFeignClients(basePackages="com.yxj.gulimall.member.feign")
public class GulimallMemberApplication {
public static void main(String[] args) {
SpringApplication.run(GulimallMemberApplication.class, args);
}
}
10.4 那么要调用什么东西呢？就是我们刚才写的优惠券的功能，
复制函数部分，在member的com.yxj.gulimall.member.feign包下新建类：
package com.yxj.gulimall.member.feign;
import com.yxj.common.utils.R;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
@FeignClient("gulimall-coupon") //告诉spring cloud这个接口是一个远程客户端，要调用coupon服务，再去调用coupon服务/coupon/coupon/member/list对应的方法
public interface CouponFeignService {
@RequestMapping("/coupon/coupon/member/list")
public R membercoupons();//得到一个R对象
}
10.5 然后我们在member的控制层写一个测试请求
@RestController
@RequestMapping("member/member")
public class MemberController {
@Autowired
private MemberService memberService;
@Autowired
CouponFeignService couponFeignService;
@RequestMapping("/coupons")
public R test(){
MemberEntity memberEntity = new MemberEntity();
memberEntity.setNickname("张三");
R membercoupons = couponFeignService.membercoupons(); //假设张三去数据库查了后返回了张三的优惠券信息
// 打印会员和优惠券信息
return R.ok().put("member",memberEntity).put("coupons",membercoupons.get("coupons"));
}
10.6 重新启动服务
http://localhost:8000/member/member/coupons
{"msg":"success","code":0,"coupons":[{"id":null,"couponType":null,"couponImg":null,"couponName":"满100减10","num":null,"amount":null,"perLimit":null,"minPoint":null,"startTime":null,"endTime":null,"useType":null,"note":null,"publishCount":null,"useCount":null,"receiveCount":null,"enableStartTime":null,"enableEndTime":null,"code":null,"memberLevel":null,"publish":null}],"member":{"id":null,"levelId":null,"username":null,"password":null,"nickname":"张三","mobile":null,"email":null,"header":null,"gender":null,"birth":null,"city":null,"job":null,"sign":null,"sourceType":null,"integration":null,"growth":null,"status":null,"createTime":null}}
10.7 上面内容很重要，我们停留5分钟体会一下
coupon里的R.ok()是什么 # coupon里的控制层就是new了个couponEntity然后放到hashmap（R）里而已。
public class R extends HashMap<String, Object> {
public static R ok() {
return new R();
}
public R put(String key, Object value) {
super.put(key, value);
return this;
}
}