[ Spring ] Spring Cloud Gateway 2025 Comprehensive Overview

Spring Gateway Architecture

• Service Center : register and find service provider
• Service Provider : programs that provide actual service
• Gateway Service : dispatch client requests to service providers

data flow : request => gateway => service center => service provider

Project Level Dependency

pluginManagement {
    repositories {
        gradlePluginPortal()
        google()
        mavenCentral()
    }
}

dependencyResolutionManagement {
    repositoriesMode = RepositoriesMode.PREFER_SETTINGS
    repositories {
        gradlePluginPortal()
        google()
        mavenCentral()
    }
}

buildscript {
    repositories {
        gradlePluginPortal()
        google()
        mavenCentral()
    }
}

plugins {
    id("org.jetbrains.kotlin.jvm") version "2.0.21" apply false
    id("org.jetbrains.kotlin.kapt") version "2.0.21" apply false
    id("org.jetbrains.kotlin.plugin.spring") version "2.0.21" apply false
    id("org.springframework.boot") version "3.4.1" apply false
}

include("eureka-server")
include("spring-gateway-service")
include("spring-gateway-provider")

Service Center

plugins {
    id("org.jetbrains.kotlin.jvm")
    id("org.jetbrains.kotlin.kapt")
    id("org.jetbrains.kotlin.plugin.spring")
    id("org.springframework.boot")
}

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

dependencies {
    // commons
    api("io.github.hellogoogle2000:kotlin-commons:1.0.19")
    // kotlin
    api("org.jetbrains.kotlin:kotlin-reflect:2.0.21")
    // spring
    api("org.springframework.boot:spring-boot-starter:3.4.1")
    api("org.springframework.boot:spring-boot-starter-web:3.4.1")
    api("org.springframework.boot:spring-boot-devtools:3.4.1")
    // eureka
    api("org.springframework.cloud:spring-cloud-starter-netflix-eureka-server:4.2.0")
}

# service
server.port=10001
spring.application.name=eureka-server
# eureka
eureka.instance.hostname=localhost
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.client.service-url.defaultZone=http://localhost:10001/eureka/

package x.spring.hello

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer

@EnableEurekaServer
@SpringBootApplication
class EurekaServerApplication

fun main(args: Array<String>) {
    runApplication<EurekaServerApplication>(*args)
}

Service Provider

plugins {
    id("org.jetbrains.kotlin.jvm")
    id("org.jetbrains.kotlin.kapt")
    id("org.jetbrains.kotlin.plugin.spring")
    id("org.springframework.boot")
}

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

dependencies {
    // commons
    api("io.github.hellogoogle2000:kotlin-commons:1.0.19")
    // kotlin
    api("org.jetbrains.kotlin:kotlin-reflect:2.0.21")
    // spring
    api("org.springframework.boot:spring-boot-starter:3.4.1")
    api("org.springframework.boot:spring-boot-starter-web:3.4.1")
    // eureka
    api("org.springframework.cloud:spring-cloud-starter-netflix-eureka-client:4.2.0")
}

# service
server.port=10003
spring.application.name=gateway-provider
# eureka
eureka.client.register-with-eureka=true
eureka.client.fetch-registry=true
eureka.client.service-url.defaultZone=http://localhost:10001/eureka/

package x.spring.hello

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication

@SpringBootApplication
class GatewayProviderApplication

fun main(args: Array<String>) {
    runApplication<GatewayProviderApplication>(*args)
}

package x.spring.hello.controller

import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.PathVariable
import org.springframework.web.bind.annotation.RestController

@RestController
class ConfigController {

    @GetMapping("/config/{key}")
    fun index(@PathVariable("key") key: String): String {
        return "config service provider on 10003 key=$key"
    }
}

Gateway Service

plugins {
    id("org.jetbrains.kotlin.jvm")
    id("org.jetbrains.kotlin.kapt")
    id("org.jetbrains.kotlin.plugin.spring")
    id("org.springframework.boot")
}

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

dependencies {
    val springBootVersion = "3.4.1"
    val springCloudVersion = "4.2.0"
    // commons
    api("io.github.hellogoogle2000:kotlin-commons:1.0.19")
    // kotlin
    api("org.jetbrains.kotlin:kotlin-reflect:2.0.21")
    // spring
    api("org.springframework.boot:spring-boot-starter:$springBootVersion")
    api("org.springframework.boot:spring-boot-devtools:$springBootVersion")
    api("org.springframework.cloud:spring-cloud-starter-bootstrap:$springCloudVersion")
    // spring cloud gateway
    api("org.springframework.boot:spring-boot-starter-webflux:$springBootVersion")
    api("org.springframework.cloud:spring-cloud-starter-gateway:$springCloudVersion")
    api("org.springframework.cloud:spring-cloud-starter-netflix-eureka-client:$springCloudVersion")
    api("javax.servlet:javax.servlet-api:4.0.1")
}

# service
server.port=10002
spring.application.name=gateway-service
# eureka
eureka.client.register-with-eureka=true
eureka.client.fetch-registry=true
eureka.client.service-url.defaultZone=http://localhost:10001/eureka/
# gateway
spring.cloud.gateway.routes[0].id=config
spring.cloud.gateway.routes[0].uri=lb://gateway-provider
spring.cloud.gateway.routes[0].predicates[0]=Path=/config/**
# http://localhost:10002/config/name => http://localhost:10003/config/name

package x.spring.hello

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication

@SpringBootApplication
class GatewayServiceApplication

fun main(args: Array<String>) {
    runApplication<GatewayServiceApplication>(*args)
}

package x.spring.hello.component

import org.springframework.cloud.gateway.route.RouteLocator
import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder
import org.springframework.cloud.gateway.route.builder.filters
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration

@Configuration
class GatewayRule {

    @Bean
    fun rule(builder: RouteLocatorBuilder): RouteLocator {
        val routes = builder.routes()
        // http://localhost:10002/github/byteflys => https://github.com/byteflys
        routes.route("csdn") { route ->
            route.filters {
                rewritePath("/github/(?<variable>.*)", "/\${variable}")
            }
            route.path("/github/**").uri("https://github.com/")
        }
        return routes.build()
    }
}

Launch All Service

http://localhost:10001
http://localhost:10003/config/name
http://localhost:10002/config/name => http://localhost:10003/config/name
http://localhost:10002/github/byteflys => https://github.com/byteflys