一 介绍

在很多次场景下，外部请求需要查询Zuul后端的多个微服务。举个例子，一个电影售票手机APP，在购票订单页上，既需要查询“电影微服务”获得电影相关信息，又需要查询“用户微服务”获得当前用户的信息。如果让手机端直接请求各个微服务（即使使用Zuul进行转发），那么网络开销、流量耗费、耗费时长可能都无法令人满意。那么对于这种场景，可使用Zuul聚合微服务请求——手机APP只需发送一个请求给Zuul，由于Zuul请求用户微服务以及电影微服务，并组织好数据给手机APP。

使用这种方式，手机端只须发送一次请求即可，简化了客户端侧的开发；不仅如此，由于Zuul、用户微服务、电影微服务一般都在同一局域网，因此速度非常快，效率会非常高。

下面围绕以上这个场景，来编写代码。

在本例中，使用了RxJava结合Zuul来实现微服务请求的聚合。

二 新建项目microservice-gateway-zuul-aggregation

三 修改启动类

package com.itmuch.cloud.study;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;@SpringBootApplication
@EnableZuulProxy
public class ZuulApplication {public static void main(String[] args) {SpringApplication.run(ZuulApplication.class, args);}@Bean@LoadBalancedpublic RestTemplate restTemplate() {return new RestTemplate();}
}

四 创建实体类

package com.itmuch.cloud.study;
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 id;}public void setId(Long id) {this.id = id;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public BigDecimal getBalance() {return balance;}public void setBalance(BigDecimal balance) {this.balance = balance;}
}

五 创建聚合服务

package com.itmuch.cloud.study;import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
import rx.Observable;@Service
public class AggregationService {@Autowiredprivate RestTemplate restTemplate;@HystrixCommand(fallbackMethod = "fallback")public Observable<User> getUserById(Long id) {// 创建一个被观察者return Observable.create(observer -> {// 请求用户微服务的/{id}端点User user = restTemplate.getForObject("http://microservice-provider-user/{id}", User.class, id);observer.onNext(user);observer.onCompleted();});}@HystrixCommand(fallbackMethod = "fallback")public Observable<User> getMovieUserByUserId(Long id) {return Observable.create(observer -> {// 请求电影微服务的/user/{id}端点User movieUser = restTemplate.getForObject("http://microservice-consumer-movie/user/{id}", User.class, id);observer.onNext(movieUser);observer.onCompleted();});}public User fallback(Long id) {User user = new User();user.setId(-1L);return user;}
}

六 创建Controller，在Controller中聚合多个请求

package com.itmuch.cloud.study;import com.google.common.collect.Maps;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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 org.springframework.web.context.request.async.DeferredResult;
import rx.Observable;
import rx.Observer;import java.util.HashMap;@RestController
public class AggregationController {public static final Logger LOGGER = LoggerFactory.getLogger(ZuulApplication.class);@Autowiredprivate AggregationService aggregationService;@GetMapping("/aggregate/{id}")public DeferredResult<HashMap<String, User>> aggregate(@PathVariable Long id) {Observable<HashMap<String, User>> result = this.aggregateObservable(id);return this.toDeferredResult(result);}public Observable<HashMap<String, User>> aggregateObservable(Long id) {// 合并两个或者多个Observables发射出的数据项，根据指定的函数变换它们return Observable.zip(this.aggregationService.getUserById(id),this.aggregationService.getMovieUserByUserId(id),(user, movieUser) -> {HashMap<String, User> map = Maps.newHashMap();map.put("user", user);map.put("movieUser", movieUser);return map;});}public DeferredResult<HashMap<String, User>> toDeferredResult(Observable<HashMap<String, User>> details) {DeferredResult<HashMap<String, User>> result = new DeferredResult<>();// 订阅details.subscribe(new Observer<HashMap<String, User>>() {@Overridepublic void onCompleted() {LOGGER.info("完成...");}@Overridepublic void onError(Throwable throwable) {LOGGER.error("发生错误...", throwable);}@Overridepublic void onNext(HashMap<String, User> movieDetails) {result.setResult(movieDetails);}});return result;}
}

七 微服务聚合测试

1 启动eureka

2 启动user微服务

3 启动movie微服务

4 启动聚合微服务

5 访问http://localhost:8040/aggregate/1

{"movieUser":{"id":1,"username":"account1","name":"张三","age":20,"balance":100.00},"user":{"id":1,"username":"account1","name":"张三","age":20,"balance":100.00}}

说明已成功聚合了用户微服务以及电影微服务的RESTful API

八 Hystrix容错测试

1 停止user微服务

2 停止movie微服务

3 访问 http://localhost:8040/aggregate/1

{"movieUser":{"id":-1,"username":null,"name":null,"age":null,"balance":null},"user":{"id":-1,"username":null,"name":null,"age":null,"balance":null}}

说明fallback方法正常被触发，能够正常回退。