Spring Cloud Gateway in Spring Boot
Spring Cloud Gateway is a Spring Boot-based gateway framework that provides a unified entry to route all requests to different backend services. Spring Cloud Gateway adopts the Reactive programming model, which can handle a large number of concurrent requests, and also has functions such as load balancing, fusing, and current limiting. This article will introduce the principle and usage of Spring Cloud Gateway.
The principle of Spring Cloud Gateway
The principle of Spring Cloud Gateway is to forward requests to different backend services through routing rules. In Spring Cloud Gateway, routing rules are defined through a Bean named RouteLocator. RouteLocator defines a set of routing rules, each routing rule contains a request path and an address of a target service.
When a request enters Spring Cloud Gateway, it will forward the request to the corresponding target service according to the routing rules. When forwarding requests, Spring Cloud Gateway can also perform some additional processing, such as load balancing, fusing, current limiting, etc.
How to use Spring Cloud Gateway
To use Spring Cloud Gateway, we need to do the following steps:
- Introduce Spring Cloud dependencies
We need to introduce Spring Cloud dependencies in the project's pom.xml file. Specifically, we need to introduce the following dependencies:
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>
- Configure routing rules
We need to configure routing rules in the application.yml or application.properties file as follows:
server:
port: 8080
spring:
cloud:
gateway:
routes:
- id: demo-service
uri: http://localhost:9000
predicates:
- Path=/demo/**
In this configuration, we define a routing rule called demo-service, which forwards all requests starting with /demo to the service with the address http://localhost:9000.
- Run the Spring Boot application
When we have completed the above configuration, we can start the Spring Boot application. When the application starts, it will automatically listen to port 8080 and forward the request to the corresponding target service according to the routing rules.
routing rules
In Spring Cloud Gateway, routing rules are defined through a Bean named RouteLocator. RouteLocator defines a set of routing rules, each routing rule contains a request path and an address of a target service. Routing rules can be defined in the following ways:
@Configuration
public class GatewayConfig {
@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
return builder.routes()
.route("demo-service", r -> r.path("/demo/**").uri("http://localhost:9000"))
.build();
}
}
In this configuration, we define a routing rule named demo-service through a Bean named customRouteLocator, which forwards all requests starting with /demo to the service whose address is http://localhost:9000.
filter
In Spring Cloud Gateway, a filter is a component that performs some action before or after the request reaches the target service. Filters can be used for operations such as request filtering, response filtering, and request transformation. There are many filters built into Spring Cloud Gateway, and we can also customize filters according to our needs.
In Spring Cloud Gateway, filters are defined through a Bean named GatewayFilter. GatewayFilter defines a filter that can perform some action before or after the request reaches the target service. Filters can be defined in the following ways:
@Configuration
public class GatewayConfig {
@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
return builder.routes()
.route("demo-service", r -> r.path("/demo/**").filters(f -> f.addRequestHeader("X-Request-Foo", "Bar")).uri("http://localhost:9000"))
.build();
}
}
In this configuration, we add a request header named X-Request-Foo with a value of Bar through the addRequestHeader method. This filter will be executed before the request reaches the target service.
sample code
Here is a simple example code showing how to use Spring Cloud Gateway to forward requests to backend services:
@Configuration
public class GatewayConfig {
@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
return builder.routes()
.route("demo-service", r -> r.path("/demo/**").uri("http://localhost:9000"))
.build();
}
}
@SpringBootApplication
@EnableDiscoveryClient
public class GatewayApplication {
public static void main(String[] args) {
SpringApplication.run(GatewayApplication.class, args);
}
}
In this example, we create a Spring Boot application called GatewayApplication and register it with the Eureka registry. We define a Bean named customRouteLocator in the GatewayConfig class, which contains a routing rule named demo-service, and forwards all requests starting with /demo to the service whose address is http://localhost:9000. At the same time, we added the @EnableDiscoveryClient annotation to the startup class to register the application with the Eureka registry.
in conclusion
Spring Cloud Gateway is a Spring Boot-based gateway framework that provides a unified entry to route all requests to different backend services. Spring Cloud Gateway adopts the Reactive programming model, which can handle a large number of concurrent requests, and also has functions such as load balancing, fusing, and current limiting. In actual projects, using Spring Cloud Gateway can make our microservice architecture more flexible and reliable.