Basic use of gateway

Spring Cloud Gateway yes Spring Cloud A brand new project , The project is based on Spring 5.0,Spring Boot 2.0 and Project Reactor Gateway developed by responsive programming and event flow technology , It aims to provide a simple and effective unified approach to microservice architecture API Routing management .

1. Why do I need a gateway

Gateway function ：

• Authentication and authority verification
• Service routing 、 Load balancing
• Request current limiting

2. Technical implementation of gateway

• stay SpringCloud The implementation of gateway in includes two methods ：
  1、gateway
  2、zuul
• Zuul Is based on Servlet The implementation of the , It belongs to blocking programming . and SpringCloudGateway Is based on Spring5 Provided in WebFlux, It belongs to the implementation of responsive programming , Better performance .

3. Summary ：

The function of gateway ：
1、 Authenticate user requests 、 Permission to check
2、 Route user requests to microservices , And load balancing
3、 Limit the current of user requests

• Access control ： The gateway acts as a microservice portal , You need to verify whether the user is qualified to request , If not, intercept .

• Routing and load balancing ： All requests must go through first gateway, But the gateway doesn't handle business , But according to some rule , Forward the request to a micro service , This process is called routing . Of course, when there are multiple target services for routing , You also need to do load balancing .

• Current limiting ： When the request traffic is too high , In the gateway, the request is released at a speed acceptable to obscene microservices , Avoid excessive service pressure .

4. Build gateway service

Steps of setting up gateway service ：

1. Create a new module, introduce Spring Cloud Gateway Dependence and Nacos Service discovery depends on

<!-- gateway -->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>

<!--nacos Service discovery depends on -->
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>

2. Write basic configuration and routing rules and nacos Address

server:
  port: 10010 #  Gateway port 
spring:
  application:
    name: gateway #  The service name 
  cloud:
    nacos:
      server-addr: 47.107.53.146:8848 # nacos Address 
    gateway:
      routes: #  Gateway routing configuration 
        - id: user-service #  route id, Customize , As long as it's the only one 
          # uri: http://127.0.0.1:8081 #  The destination address of the route  http It's a fixed address 
          uri: lb://userservice #  The destination address of the route  lb It's load balancing , Followed by the service name 
          predicates: #  Route assertion , That is, judge whether the request meets the conditions of routing rules 
            - Path=/user/** #  This is matched according to the path , As long as /user/ Meet the requirements at the beginning 

• Will conform to Path All requests of the rules , All agents arrive at uri The address specified by the parameter
• In this case , take /user/** Initial request , Proxy to lb://userservice,lb It's load balancing , Pull the service list according to the service name , Load balancing .
• Flow chart of gateway routing , The whole access process is as follows ：
  

4. Restart test ：
   Restart gateway , visit http://localhost:10010/user/1 when , accord with /user/** The rules , Request forwarding to uri：http://userservice/user/1, Got the result ：
   

• visit http://localhost:10010/order/101 , accord with /order/** The rules , Request forwarding to uri:http://orderservice/order/101, Get the results ：
  

5. Summary

1、 Create project , introduce nacos Service discovery and gateway rely on
2、 To configure application.yml, Including basic service information 、nacos Address 、 route

• Routing configuration includes ：

1、 route id： The unique identifier of the route
2、 Routing destination （uri）： The destination address of the route ,http Represents a fixed address ,lb Represents load balancing based on service name
3、 Route assertion （predicates）： Rules for judging routing ,
4、 Routing filter （filters）： To process a request or response

6. Route assertion factory Route Predicate Factory

Gateway routing can be configured as follows ：

• route id： Route unique identification
• uri： Route destination , Support lb and http Two kinds of
• predicates： Route assertion , Determine whether the request meets the requirements , If yes, it will be forwarded to the routing destination
• filters： Routing filter , Process a request or response

---

• The assertion rules written in the configuration file are just strings , These strings will be Predicate Factory Read and process , The condition for changing to routing judgment
• for example Path=/user/** Is to match according to the path , This rule is made by org.springframework.cloud.gateway.handler.predicate.PathRoutePredicateFactory Class to handle
• Assertion factories like this are SpringCloudGateway There are more than a dozen

---

Spring Provides 11 Species basic Predicate factory ：

• Such as ： hold orderservice Set at 2023 Requests after , Obviously, it does not meet the requirements , newspaper 404 error
  
  

• Assertions can be made according to requirements Predicate Make relevant settings , Official document ：
  https://docs.spring.io/spring-cloud-gateway/docs/current/reference/html/#gateway-request-predicates-factories

7. Summary

• PredicateFactory What is the role of ？
  Read user-defined assertion conditions , Make a judgment on the request
• Path=/user/** What does it mean ？
  The path is /user The beginning is considered to be consistent

8. Routing filter GatewayFilter

• GatewayFilter It is a filter provided in the gateway , You can process the request to enter the gateway and the response returned by the microservice ：
  

• Spring Provides 31 There are different routing filter factories . for example ：

name	explain
AddRequestHeader	Add a request header to the current request
RemoveRequestHeader	Remove a request header from the request
AddResponseHeader	Add a response header to the response result
RemoveResponseHeader	Remove a response header from the response result
RequestRateLimiter	Limit the requested traffic

• Official website ：https://docs.spring.io/spring-cloud-gateway/docs/current/reference/html/#gatewayfilter-factories

9. Request header filter

Let's say AddRequestHeader For example to explain ：

• Give everyone access userservice Add a request header to your request ：Truth=Just Do It!
• Realization way ： stay gateway Revision in China application.yml file , to userservice Add filter for route ：

spring:
  cloud:
    gateway:
      routes:
      - id: user-service 
        uri: lb://userservice 
        predicates: 
        - Path=/user/** 
        filters: #  filter 
        - AddRequestHeader=Truth, Just Do It! #  Add request header 

• stay userservice Under the UserController Add the printed request header information under
  

• restart userservice, After visiting, you can see ：
  

• The current filter is written in userservice Under route , So just access userservice Your request is valid

---

10. Default filter

• If you want to be effective for all routes , The filter factory can be written to default Next . The format is as follows ：

spring:
  cloud:
    gateway:
      routes:
      - id: user-service 
        uri: lb://userservice 
        predicates: 
        - Path=/user/**
      default-filters: #  Default filter 
      - AddRequestHeader=Truth, Just Do It! 

11. Summary

• What is the function of the filter ？

① Process the routed request or response , For example, add request headers

② The filter configured under the route is only effective for the requests of the current route

• defaultFilters What is the role of ？

① Filters in effect for all routes

12. Global filter GlobalFilter

• The global filter is also used to handle all requests and microservice responses entering the gateway , And GatewayFilter It does the same thing .
• The difference lies in GatewayFilter Defined by configuration , The processing logic is fixed . and GlobalFilter You need to write your own code to implement your logic .
• The definition is to implement GlobalFilter Interface .

public interface GlobalFilter {
    
    /** *  Process the current request , If necessary, through {@link GatewayFilterChain} Pass the request to the next filter  * * @param exchange  Request context , You can get Request、Response Etc  * @param chain  Used to delegate the request to the next filter  * @return {@code Mono<Void>}  Return to indicate the end of the current filter business  */
    Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain);
}

• Define global filters , Intercept and determine the user's identity
  demand ： Define global filters , Intercept request , Judge whether the requested parameters meet the following conditions ：
  Whether there is authorization,
  authorization Whether the parameter value is admin
  If both are met, release , Otherwise intercept

• Custom class , Realization GlobalFilter Interface , add to @Order annotation , stay gateway Define a filter in ：

@Order(-1)
@Component
public class AuthorizeFilter implements GlobalFilter  {
    

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
    
        // 1.  Get request parameters 
        ServerHttpRequest request = exchange.getRequest();
        MultiValueMap<String, String> params = request.getQueryParams();
        // 2.  Get... In the request parameter authorization  Parameters 
        String auth = params.getFirst("authorization");
        // 3.  Judge whether the parameter is equal to  admin
        if ("admin".equals(auth)) {
    
            // 4.  yes , release 
            return chain.filter(exchange);
        }

        // 5.  no , Intercept 
        // 5.1  Set status code 
        exchange.getResponse().setStatusCode(HttpStatus.UNAUTHORIZED);
        // 5.2  Intercept request 
        return exchange.getResponse().setComplete();

    }
}

• When the specified slave parameter is not brought when accessing the service , The set status code will be reported 401
  
  

• With parameters, you can normally access ：
  

13. Summary

• What is the role of the global filter ？
  Filters in effect for all routes , And you can customize the processing logic
• Steps to implement the global filter ？
  ① Realization GlobalFilter Interface
  ② add to @Order To annotate or implement Ordered Interface
  ③ Write processing logic

14. Filter execution order

• The request to enter the gateway will encounter three types of filters ： Filter for the current route 、DefaultFilter、GlobalFilter

• After request routing , The current route filter and DefaultFilter、GlobalFilter, Merge into a filter chain （ aggregate ） in , After sorting, execute each filter in turn
  

• Each filter must specify a int Type of order value ,order The smaller the value. , The higher the priority , The higher the order of execution .

• GlobalFilter By implementing Ordered Interface , Or add @Order Note to specify order value , It's up to us to designate

• Routing filters and defaultFilter Of order from Spring Appoint , The default is from... In the order of declaration 1 Increasing .

• When the filter order When the value is the same , According to defaultFilter > Routing filter > GlobalFilter Sequential execution .

• You can refer to the source code of the following classes to view ：

org.springframework.cloud.gateway.route.RouteDefinitionRouteLocator
#getFilters() The method is to load defaultFilters, Then load a route Of filters, Then merge .

org.springframework.cloud.gateway.handler.FilteringWebHandler
#handle() Method loads the global filter , Combined with the previous filter, according to order Sort , Organize the filter chain 

15. Summary

• Routing filter 、defaultFilter、 The execution order of the global filter ？
  ①order The smaller the value. , The higher the priority
  ② When order When the value is the same , The order is defaultFilter The first , Then there is the local routing filter , Finally, the global filter

16. Cross domain problem handling

• Cross domain ： Domain name inconsistency is cross domain , It mainly includes ：
  1、 Domain name is different ： www.taobao.com and www.taobao.org and www.jd.com and miaosha.jd.com
  2、 Domain name is the same , Different ports ：localhost:8080 and localhost8081

• Cross-domain problem ： The browser prohibits cross domain communication between the initiator of the request and the server ajax request , The request is blocked by the browser

• Solution ：CORS

• The gateway handles cross domain transactions in the same way CORS programme , And it only needs simple configuration to realize ：

spring:
  cloud:
    gateway:
      # ...
      globalcors: #  Global cross domain processing 
        add-to-simple-url-handler-mapping: true #  solve options The request is blocked 
        corsConfigurations:
          '[/**]':
            allowedOrigins: #  Allow cross domain requests for which websites  
              - "http://localhost:8090"
            allowedMethods: #  Allowed cross domain ajax Request method of 
              - "GET"
              - "POST"
              - "DELETE"
              - "PUT"
              - "OPTIONS"
            allowedHeaders: "*" #  Header information allowed to be carried in the request 
            allowCredentials: true #  Is it allowed to carry cookie
            maxAge: 360000 #  The validity period of this cross domain detection