前面分别对 Spring Cloud Zuul 与 Spring Cloud Gateway 进行了简单的说明，它门是API网关，API网关负责服务请求路由、组合及协议转换，客户端的所有请求都首先经过API网关，然后由它将匹配的请求路由到合适的微服务，是系统流量的入口，在实际生产环境中为了保证高可靠和高可用，尽量避免重启，如果有新的服务要上线时，可以通过动态路由配置功能上线。
本篇拿 Spring Cloud Gateway 为例，对网关的动态路由进行简单分析，下一篇将分享动态路由的进阶实现
# 暴露端点
management:
endpoints:
web:
exposure:
include: '*'
endpoint:
health:
show-details: always 前提：需要启动 3个服务，eureka、gateway、consumer-service
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency> //1.创建路由模型
public class GatewayRouteDefinition {
//路由的Id
private String id;
//路由断言集合配置
private List<GatewayPredicateDefinition> predicates = new ArrayList<>();
//路由过滤器集合配置
private List<GatewayFilterDefinition> filters = new ArrayList<>();
//路由规则转发的目标uri
private String uri;
//路由执行的顺序
private int order = 0;
//此处省略get和set方法
}
//2.创建过滤器模型
public class GatewayFilterDefinition {
//Filter Name
private String name;
//对应的路由规则
private Map<String, String> args = new LinkedHashMap<>();
//此处省略Get和Set方法
}
//3.路由断言模型
public class GatewayPredicateDefinition {
//断言对应的Name
private String name;
//配置的断言规则
private Map<String, String> args = new LinkedHashMap<>();
//此处省略Get和Set方法
} /**
* 动态路由服务
*/
@Service
public class DynamicRouteServiceImpl implements ApplicationEventPublisherAware{
@Autowired
private RouteDefinitionWriter routeDefinitionWriter;
private ApplicationEventPublisher publisher;
@Override
public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
this.publisher = applicationEventPublisher;
}
//增加路由
public String add(RouteDefinition definition) {
routeDefinitionWriter.save(Mono.just(definition)).subscribe();
this.publisher.publishEvent(new RefreshRoutesEvent(this));
return "success";
}
//更新路由
public String update(RouteDefinition definition) {
try {
delete(definition.getId());
} catch (Exception e) {
return "update fail,not find route routeId: "+definition.getId();
}
try {
routeDefinitionWriter.save(Mono.just(definition)).subscribe();
this.publisher.publishEvent(new RefreshRoutesEvent(this));
return "success";
} catch (Exception e) {
return "update route fail";
}
}
//删除路由
public Mono<ResponseEntity<Object>> delete(String id) {
return this.routeDefinitionWriter.delete(Mono.just(id)).then(Mono.defer(() -> {
return Mono.just(ResponseEntity.ok().build());
})).onErrorResume((t) -> {
return t instanceof NotFoundException;
}, (t) -> {
return Mono.just(ResponseEntity.notFound().build());
});
}
} @RestController
@RequestMapping("/route")
public class RouteController {
@Autowired
private DynamicRouteServiceImpl dynamicRouteService;
//增加路由
@PostMapping("/add")
public String add(@RequestBody GatewayRouteDefinition gwdefinition) {
String flag = "fail";
try {
RouteDefinition definition = assembleRouteDefinition(gwdefinition);
flag = this.dynamicRouteService.add(definition);
} catch (Exception e) {
e.printStackTrace();
}
return flag;
}
//删除路由
@DeleteMapping("/routes/{id}")
public Mono<ResponseEntity<Object>> delete(@PathVariable String id) {
try {
return this.dynamicRouteService.delete(id);
}catch (Exception e){
e.printStackTrace();
}
return null;
}
//更新路由
@PostMapping("/update")
public String update(@RequestBody GatewayRouteDefinition gwdefinition) {
RouteDefinition definition = assembleRouteDefinition(gwdefinition);
return this.dynamicRouteService.update(definition);
}
//把传递进来的参数转换成路由对象
private RouteDefinition assembleRouteDefinition(GatewayRouteDefinition gwdefinition) {
RouteDefinition definition = new RouteDefinition();
definition.setId(gwdefinition.getId());
definition.setOrder(gwdefinition.getOrder());
//设置断言
List<PredicateDefinition> pdList=new ArrayList<>();
List<GatewayPredicateDefinition> gatewayPredicateDefinitionList=gwdefinition.getPredicates();
for (GatewayPredicateDefinition gpDefinition: gatewayPredicateDefinitionList) {
PredicateDefinition predicate = new PredicateDefinition();
predicate.setArgs(gpDefinition.getArgs());
predicate.setName(gpDefinition.getName());
pdList.add(predicate);
}
definition.setPredicates(pdList);
//设置过滤器
List<FilterDefinition> filters = new ArrayList();
List<GatewayFilterDefinition> gatewayFilters = gwdefinition.getFilters();
for(GatewayFilterDefinition filterDefinition : gatewayFilters){
FilterDefinition filter = new FilterDefinition();
filter.setName(filterDefinition.getName());
filter.setArgs(filterDefinition.getArgs());
filters.add(filter);
}
definition.setFilters(filters);
URI uri = null;
if(gwdefinition.getUri().startsWith("http")){
uri = UriComponentsBuilder.fromHttpUrl(gwdefinition.getUri()).build().toUri();
}else{
// uri为 lb://consumer-service 时使用下面的方法
uri = URI.create(gwdefinition.getUri());
}
definition.setUri(uri);
return definition;
}
} 
本篇博客参考了许进的文章，地址： http://springcloud.cn/view/407，还有他写的 《重新定义SpringCloud》比较不错
代码已上传至码云， 源码，项目使用的版本信息如下：
- SpringBoot 2.0.6.RELEASE
- SpringCloud Finchley.SR2 下篇将介绍动态路由的进阶实现，实现方式：