1. Introduction and core concepts of Spring Cloud Gateway
In the microservice architecture, the API gateway is a very important component, which can help us implement functions such as service routing, load balancing, authentication and authorization. Spring Cloud Gateway is an API gateway implementation based on Spring 5, Spring Boot 2 and Project Reactor officially launched by Spring Cloud. This article will introduce the basic concepts, core components and how to configure and use Spring Cloud Gateway.
1.1. What is Spring Cloud Gateway
Spring Cloud Gateway is an API gateway implementation based on Spring Boot, Spring WebFlux and Project Reactor, which provides a simple and efficient way to build an API gateway in a microservice architecture. The main functions of Spring Cloud Gateway include:
- Routing: forward the request to the corresponding microservice according to the requested path, method and other information
- Filtering: process requests before or after they are forwarded, such as adding, modifying request headers, response headers, etc.
- Assertion: Judging whether a condition is met based on the requested information, such as whether the request path matches a regular expression
- Load balancing: distribute requests among multiple instances for high availability and performance
1.2. Comparison between Spring Cloud Gateway and other API gateways
There are many implementations of API gateways on the market, such as Nginx, Zuul, Kong, etc. Compared with these API gateways, Spring Cloud Gateway has the following advantages:
- Based on Spring Boot and Spring Cloud, it is more tightly integrated with the Spring ecosystem
- Higher performance using non-blocking I/O and a reactive programming model
- Provides a wealth of filters and assertions, which can easily implement various functions
- Support dynamic routing and dynamic configuration, more flexible
1.3. Core components of Spring Cloud Gateway
The core components of Spring Cloud Gateway mainly include the following:
- Route: A route is the basic building block of a gateway, which defines how requests are forwarded to microservices. A route consists of an ID, an assertion and a filter chain.
- Predicate: An assertion is used to determine whether a request satisfies a certain condition, such as whether the request path matches a regular expression. Assertions can be used to selectively apply filters or route requests.
- Filter (filter): The filter is used to process the request before or after the request is forwarded, such as adding and modifying request headers, response headers, etc. Filters are divided into local filters and global filters. Local filters only work on specific routes, while global filters work on all routes.
- LoadBalancer: A load balancer is used to distribute requests among multiple instances for high availability and high performance. Spring Cloud Gateway integrates Spring Cloud LoadBalancer, which can easily achieve load balancing.
2. Configuration and use of Spring Cloud Gateway
Next, we will introduce how to build and configure Spring Cloud Gateway, and how to use functions such as assertions, filters, and routing.
2.1. How to build and configure Spring Cloud Gateway
To build a Spring Cloud Gateway project, you first need to create a Spring Boot project and add the following dependencies:
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>
Then, configure Spring Cloud Gateway in the application.ymlor application.propertiesfile as follows:
spring:
cloud:
gateway:
routes:
- id: user-service
uri: lb://user-service
predicates:
- Path=/user/**
filters:
- StripPrefix=1
The above configuration defines a user-serviceroute named , when the request path /userstarts with , the request will be forwarded to user-servicethe microservice. StripPrefix=1Indicates to strip the first part of the path (ie ) before forwarding the request /user.
2.2. Use of assertions
2.2.1. Built-in assertions
Spring Cloud Gateway provides some built-in assertions, such as Path, Method, Headeretc. Here are some examples of commonly used built-in assertions:
Path=/user/**: Match/userrequests whose path starts withMethod=GET: Matches GET requestsHeader=X-Requested-With, XMLHttpRequest: Match requests that containX-Requested-Witha header with a value ofXMLHttpRequest
2.2.2. Custom assertions
In addition to built-in assertions, we can also customize assertions. To create a custom assertion, implement GatewayPredicatethe interface and register it as a Spring Bean. Here is an example of a simple custom assertion:
@Component
public class CustomPredicate implements GatewayPredicate {
@Override
public boolean test(ServerWebExchange exchange) {
// 自定义断言逻辑
return true;
}
@Override
public GatewayPredicate negate() {
return new CustomPredicate();
}
}
2.3. Use of filters
2.3.1. Local filters
Local filters are filters that only apply to specific routes. To create a partial filter, implement GatewayFilterthe interface and register it as a Spring Bean. Here is an example of a simple partial filter:
@Component
public class CustomFilter implements GatewayFilter {
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
// 在请求被转发之前的处理逻辑
return chain.filter(exchange).then(Mono.fromRunnable(() -> {
// 在请求被转发之后的处理逻辑
}));
}
}
2.3.2. Global Filters
Global filters are filters that apply to all routes. To create a global filter, implement GlobalFilterthe interface and register it as a Spring Bean. Here is an example of a simple global filter:
@Component
public class CustomGlobalFilter implements GlobalFilter {
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
// 在请求被转发之前的处理逻辑
return chain.filter(exchange).then(Mono.fromRunnable(() -> {
// 在请求被转发之后的处理逻辑
}));
}
}
2.3.3. Custom Filters
In addition to the built-in filters, we can also customize filters. To create a custom filter, implement GatewayFilterFactorythe interface and register it as a Spring Bean. Here is an example of a simple custom filter:
@Component
public class CustomFilterFactory implements GatewayFilterFactory<CustomFilterFactory.Config> {
@Override
public GatewayFilter apply(Config config) {
return new CustomFilter(config);
}
@Override
public Class<Config> getConfigClass() {
return Config.class;
}
public static class Config {
// 自定义过滤器配置
}
}
2.4. Use of routing
2.4.1. Routing based on cluster load balancing
Spring Cloud Gateway integrates Spring Cloud LoadBalancer, which can easily achieve load balancing. To use load balancing, simply set the route's URI to lb://<service-id>something like this:
spring:
cloud:
gateway:
routes:
- id: user-service
uri: lb://user-service
predicates:
- Path=/user/**
2.4.2. Realization of dynamic routing
Spring Cloud Gateway supports dynamic routing, and the routing configuration can be modified at runtime. To implement dynamic routing, you need to implement RouteDefinitionLocatorthe interface and register it as a Spring Bean. Here is an example of a simple dynamic route:
@Component
public class CustomRouteDefinitionLocator implements RouteDefinitionLocator {
@Override
public Flux<RouteDefinition> getRouteDefinitions() {
// 从数据库、配置中心等地方获取路由配置
List<RouteDefinition> routeDefinitions = new ArrayList<>();
return Flux.fromIterable(routeDefinitions);
}
}
2.4.3. Retrieve the routes defined in the gateway
To retrieve the routes defined in the gateway, RouteLocatorthe interface can be used. Here is a simple example:
@Autowired
private RouteLocator routeLocator;
public void printRoutes() {
routeLocator.getRoutes().subscribe(route -> {
System.out.println("Route ID: " + route.getId());
System.out.println("Route URI: " + route.getUri());
});
}
Summarize
Through the above introduction, I believe that everyone has a certain understanding of Spring Cloud Gateway. In actual projects, we can flexibly use functions such as assertion, filter, and routing according to requirements to build a powerful API gateway with superior performance.