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## 3. spring-cloud samples
## 3. spring-cloud samples
| samples | 描述 | 官方文档 |
| ------------------------------------------------------------ | --------------------------------- | ------------------------------------------------------------ |
| [spring-cloud-Eureka](https://github.com/heibaiying/spring-samples-for-all/tree/master/spring-cloud/spring-cloud-eureka) | 服务的注册和发现 | [Service Discovery: Eureka Clients](https://cloud.spring.io/spring-cloud-static/spring-cloud-netflix/2.1.0.RC3/single/spring-cloud-netflix.html#_service_discovery_eureka_clients) |
| [spring-cloud-Eureka-cluster](https://github.com/heibaiying/spring-samples-for-all/tree/master/spring-cloud/spring-cloud-eureka-cluster) | eureka 高可用集群搭建 | |
| spring-cloud-Ribbon | 客户端负载均衡 | |
| spring-cloud-OpenFeign | 声明式服务调用 | [Spring Cloud OpenFeign 官方文档](https://spring.io/projects/spring-cloud-openfeign#learn) |
| spring-cloud-Hystrix | 服务容错与降级保护 | |
| spring-cloud-config | 分布式配置中心 | [Spring Cloud Config](https://spring.io/projects/spring-cloud-config#learn) |
| spring-cloud-stream | spring cloud 对消息服务的抽象整合 | [spring-cloud-stream官方文档](https://cloud.spring.io/spring-cloud-stream/) |
| spring-cloud-zuul | spring cloud 网关服务 | [Router and Filter: Zuul](http://projects.spring.io/spring-cloud/spring-cloud.html#_router_and_filter_zuul) |
| spring-cloud-sleuth-Zipkin | 分布式服务追踪 | [Spring Cloud Sleuth](https://spring.io/projects/spring-cloud-sleuth#learn) |
| spring-cloud-config | 分布式配置中心 | [Spring Cloud Config](https://spring.io/projects/spring-cloud-config#learn) |
| spring-cloud -bus | spring cloud 消息总线 | |
| samples | 描述 | 官方文档 |
| ------------------------------------------------------------ | ---------------------------------- | ------------------------------------------------------------ |
| spring-cloud | 微服务简介与用例说明 | |
| [spring-cloud-Eureka](https://github.com/heibaiying/spring-samples-for-all/tree/master/spring-cloud/spring-cloud-eureka) | 服务的注册和发现 | [Service Discovery: Eureka Clients](https://cloud.spring.io/spring-cloud-static/spring-cloud-netflix/2.1.0.RC3/single/spring-cloud-netflix.html#_service_discovery_eureka_clients) |
| [spring-cloud-Eureka-cluster](https://github.com/heibaiying/spring-samples-for-all/tree/master/spring-cloud/spring-cloud-eureka-cluster) | eureka 高可用集群搭建 | |
| spring-cloud-Ribbon | RestTemplate的使用、客户端负载均衡 | [ribbon](http://cloud.spring.io/spring-cloud-netflix/multi/multi_spring-cloud-ribbon.html) |
| spring-cloud-OpenFeign | 声明式服务调用 | [Spring Cloud OpenFeign 官方文档](https://spring.io/projects/spring-cloud-openfeign#learn) |
| spring-cloud-Hystrix | 熔断器 | |
| spring-cloud-zuul | 网关服务 | [Router and Filter: Zuul](http://projects.spring.io/spring-cloud/spring-cloud.html#_router_and_filter_zuul) |
| spring-cloud-sleuth-Zipkin | 分布式系统服务追踪 | [Spring Cloud Sleuth](https://spring.io/projects/spring-cloud-sleuth#learn) |
| spring-cloud-config-bus | 配置中心 + 消息总线实现配置热更新 | [Spring Cloud Config](https://spring.io/projects/spring-cloud-config#learn) |
| spring-cloud-stream | spring cloud 对消息服务的抽象整合 | [spring-cloud-stream官方文档](https://cloud.spring.io/spring-cloud-stream/) |
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# spring-cloud-ribbon
## 一、ribbon 简介
ribbon是Netfix公司开源的负载均衡组件采用服务端负载均衡的方式即消费者客户端维护可用的服务列表并通过负载均衡的方式将请求按照指定的策略分摊给消费者从而达到负载均衡的方式。
## 二、项目结构
+ common: 公共的接口和实体类;
+ consumer: 服务的消费者采用RestTemplate调用产品服务
+ producer服务的提供者
+ eureka: 注册中心ribbon 从注册中心获取可用的服务列表,是实现负载均衡的基础。这里使用我们在[服务的注册与发现](https://github.com/heibaiying/spring-samples-for-all/tree/master/spring-cloud/spring-cloud-eureka)这个用例中搭建的简单注册中心作为测试即可。
<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-cloud-ribbon.png"/> </div>
## 三、服务提供者的实现
#### 3.1 产品服务由`ProductService`提供,并通过`ProducerController`将服务暴露给外部调用。
<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/ribbon-producer.png"/> </div>
ProductService.java
```java
/**
* @author : heibaiying
* @description : 产品提供接口实现类
* 这里为了之后直观的看到负载均衡的结果,我们继承了 ApplicationListener,从 WebServerInitializedEvent 获取服务的端口号,并拼接在产品名称上
*/
@Service
public class ProductService implements IProductService, ApplicationListener<WebServerInitializedEvent> {
private static List<Product> productList = new ArrayList<>();
public Product queryProductById(int id) {
for (Product product : productList) {
if (product.getId() == id) {
return product;
}
}
return null;
}
public List<Product> queryAllProducts() {
return productList;
}
@Override
public void saveProduct(Product product) {
productList.add(product);
}
@Override
public void onApplicationEvent(WebServerInitializedEvent event) {
int port = event.getWebServer().getPort();
for (long i = 0; i < 20; i++) {
productList.add(new Product(i, port + "产品" + i, i / 2 == 0, new Date(), 66.66f * i));
}
}
}
```
ProducerController.java
```java
@RestController
public class ProducerController {
@Autowired
private IProductService productService;
@GetMapping("products")
public List<Product> productList() {
return productService.queryAllProducts();
}
@GetMapping("product/{id}")
public Product productDetail(@PathVariable int id) {
return productService.queryProductById(id);
}
@PostMapping("product")
public void save(@RequestBody Product product) {
productService.saveProduct(product);
}
}
```
#### 3.2 将服务注册到注册中心
```java
server:
port: 8020
# 指定服务命名
spring:
application:
name: producer
# 指定注册中心地址
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8010/eureka/
```
## 四、服务消费者的实现
<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/ribbon-consumer.png"/> </div>
#### 4.1 导入负载均衡需要的依赖
```xml
<!--ribbon 依赖-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>
```
#### 4.2 指定注册中心的地址
```java
server:
port: 8080
# 指定服务命名
spring:
application:
name: consumer
# 指定注册中心地址
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8010/eureka/
```
#### 4.3 使用@LoadBalanced配置RestTemplate即可实现客户端负载均衡
```java
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;
@Configuration
public class RibbonConfig {
@LoadBalanced // 配置客户端负载均衡
@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
```
#### 4.4 使用RestTemplate调用远程服务
这里我们在调用远程服务的时候url填写的是服务名+具体接口地址 ,由于我们的同一个服务会存在多个实例,在使用@LoadBalanced配置RestTemplate调用服务时客户端就会从按照指定的负载均衡的方式将请求分摊到多个实例上。默认的负载均衡采用的是RoundRobinRule轮询的策略有特殊需求时候可以采用其他内置的策略规则或者实现IRule来定义自己的负载均衡策略
```java
@Service
public class ProductService implements IProductService {
@Autowired
private RestTemplate restTemplate;
public Product queryProductById(int id) {
ResponseEntity<Product> responseEntity = restTemplate.getForEntity("http://producer/product/{1}", Product.class, id);
return responseEntity.getBody();
}
public List<Product> queryAllProducts() {
ResponseEntity<List> responseEntity = restTemplate.getForEntity("http://producer/products", List.class);
List<Product> productList = responseEntity.getBody();
return productList;
}
public void saveProduct(Product product) {
restTemplate.postForObject("http://producer/product", product, Void.class);
}
}
```
## 五、启动测试
#### 5.1 启动一个Eureka服务、三个producer服务注意区分端口、和一个消费者服务
<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-cloud-ribbon-app.png"/> </div>
**服务注册中心:**
<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-cloud-ribbon-eureka.png"/> </div>
#### 5.2 访问http://localhost:8080/sell/products 查看负载均衡的调用结果
<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-cloud-ribbon-products-8020.png"/> </div>
<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-cloud-ribbon-products-8030.png"/> </div>
## 六、 附1 关于RestTemplate的说明
#### 6.1 restTemplate 调用对应resultful接口时候使用的方法应该与接口声明方式@GetMapping@PostMapping@PutMapping@DeleteMapping)保持一致。请求类型与对应的调用方法如下。
- GET请求(getForObject 、getForEntity)
- POST请求postForObject 、postForEntity
- PUT请求put
- DELETE请求 delete
#### 6.2 ForEntity()和ForObject的区别
- `ForEntity()`发送一个请求返回的ResponseEntity包含了响应体所映射成的对象
- `ForObject()`发送一个请求,返回的请求体将映射为一个对象
例如:
```java
ResponseEntity<Product> responseEntity = restTemplate.getForEntity("http://producer/product/{1}", Product.class, id);
Product product = restTemplate.getForObject("http://producer/product/{1}", Product.class, id);
```
## 七、 附2 关于ribbon更多负载均衡的策略
Ribbon内置了多种负载均衡策略如果有更复杂的需求可以自己实现IRule。
#### 7.1 内置的负载均衡的策略如下图
![Ribbon负载均衡策略.png](http://upload-images.jianshu.io/upload_images/6944619-0355d316f5df9b3f.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
图片来源于博客:[Ribbon负载均衡策略与自定义配置](https://blog.csdn.net/jrn1012/article/details/77837680)
#### 7.2 配置文件指定负载均衡的方式
要设置`IRule`名为的服务名称`users`,您可以设置以下属性:
```yaml
users:
ribbon:
NFLoadBalancerRuleClassName: com.netflix.loadbalancer.WeightedResponseTimeRule
```
#### 7.3 代码指定负载均衡的方式
```java
@Configuration
@RibbonClient(name = "custom", configuration = CustomConfiguration.class)
public class TestConfiguration {
}
```
```java
@Configuration
public class CustomConfiguration {
@Bean
public IRule ribbonRule() {
return new BestAvailableRule();
}
}
```
在使用代码方式的时候需要注意 [官方文档](http://cloud.spring.io/spring-cloud-netflix/multi/multi_spring-cloud-ribbon.html#_customizing_the_ribbon_client)中关于注解方式有以下强调:
```properties
The CustomConfiguration clas must be a @Configuration class, but take care that it is not in a @ComponentScan for the main application context. Otherwise, it is shared by all the @RibbonClients. If you use @ComponentScan (or @SpringBootApplication), you need to take steps to avoid it being included (for instance, you can put it in a separate, non-overlapping package or specify the packages to scan explicitly in the @ComponentScan).
```
`CustomConfiguration`类必须是`@Configuration`标注的,但需要注意的它不是在`@ComponentScan`主应用程序上下文。否则,它将由所有`@RibbonClients`共享。如果你使用`@ComponentScan`(或`@SpringBootApplication`),你需要采取一些措施来避免它被扫描到(例如,你可以把它放在一个独立的,非重叠的包,或用`@ComponentScan`时显示扫描指定的包)。