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Spring Boot 4 Microservices & REST APIs · 课时

使用 Spring Cloud Gateway 构建 API 网关

设置 Spring Cloud Gateway 来路由请求、应用过滤器并保护您的微服务。

第 3 / 3 课11 个步骤

使用 Spring Cloud Gateway 构建 API 网关 是 CoddyKit 上的免费 Spring Boot 4 Microservices & REST APIs 课时。 这是第 3 节课，共 3 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Spring Boot 4 Microservices & REST APIs 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Spring Boot 4 Microservices & REST APIs 课程共包含 3 节课。

本课时的部分内容尚未翻译，以英文显示。

Why an API Gateway?

Microservices are great for building scalable applications, but they can introduce complexity. Imagine having many services, each with its own address and port.

An API Gateway acts as a single, unified entry point for all client requests. It funnels incoming traffic to the correct microservice, simplifying how clients interact with your backend.

What is Spring Cloud Gateway?

Spring Cloud Gateway (SCG) is a powerful, reactive API Gateway built on Spring Framework 5, Project Reactor, and Spring Boot 2. It's designed for high performance and scalability.

  • It provides flexible routing based on requests.
  • Enables dynamic filtering of requests and responses.
  • Integrates seamlessly with other Spring Cloud projects.

Setting Up Your Gateway Project

To create a Spring Cloud Gateway application, start with a standard Spring Boot project. The key is to add the spring-cloud-starter-gateway dependency.

This dependency pulls in everything needed to transform your Spring Boot app into an intelligent gateway. Remember to include the spring-cloud-dependencies in your dependencyManagement section.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.2.5</version>
    <relativePath/>
  </parent>
  <groupId>com.coddykit</groupId>
  <artifactId>gateway</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>gateway</name>
  <description>Demo project for Spring Cloud Gateway</description>
  <properties>
    <java.version>17</java.version>
    <spring-cloud.version>2023.0.1</spring-cloud.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-gateway</artifactId>
    </dependency>
  </dependencies>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>${spring-cloud.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>
</project>

Defining Basic Routes

Routes are the core of an API Gateway. They tell the gateway how to forward incoming requests to the correct backend service. Routes are defined using predicates and a target URI.

Here, the Path=/hello/** predicate matches any request path starting with /hello/ and routes it to http://localhost:8081.

server:
  port: 8080

spring:
  application:
    name: api-gateway
  cloud:
    gateway:
      routes:
        - id: hello_route
          uri: http://localhost:8081
          predicates:
            - Path=/hello/**

Testing Your Gateway Route

To test the route, you'd typically have a backend microservice running. Let's imagine a simple 'hello-service' running on http://localhost:8081 that responds to any /hello/** path.

  • Start your Gateway application (e.g., on port 8080).
  • Make a request to http://localhost:8080/hello/world.
  • The Gateway intercepts it and forwards it to http://localhost:8081/hello/world.
  • The response from 'hello-service' is then sent back to the client via the Gateway.

Introducing Gateway Filters

Gateway Filters are functions that allow you to modify requests and responses as they pass through the gateway. They are incredibly powerful for implementing cross-cutting concerns.

  • Request Filters: Modify the request before it reaches the target service.
  • Response Filters: Modify the response before it's sent back to the client.

Filters can be applied globally to all routes or specifically to individual routes.

Applying a Simple Filter: AddRequestHeader

Let's enhance our hello_route with a filter. The AddRequestHeader filter is a built-in filter that adds a specified header to the request before forwarding it.

This is useful for injecting correlation IDs, security tokens, or origin information into requests sent to downstream services.

server:
  port: 8080

spring:
  application:
    name: api-gateway
  cloud:
    gateway:
      routes:
        - id: hello_route_with_header
          uri: http://localhost:8081
          predicates:
            - Path=/hello/**
          filters:
            - AddRequestHeader=X-Request-Source, Gateway

Centralizing Security with Gateway

An API Gateway is an ideal place to centralize security mechanisms for your microservices. Instead of implementing authentication and authorization in every service, the gateway can handle it once.

  • Authentication: Validate user credentials or tokens (e.g., JWT).
  • Authorization: Check if the authenticated user has permission for the requested resource.
  • If checks pass, the request proceeds; otherwise, it's rejected at the gateway level.

Beyond Built-in Filters: Custom Filters

While Spring Cloud Gateway provides many useful built-in filters, you might need custom logic. You can create your own filters by implementing the GlobalFilter and Ordered interfaces.

Custom filters are perfect for unique logging requirements, advanced metrics collection, or bespoke security checks that apply across your entire API landscape.

Gateway Concepts Check

Test your understanding of API Gateway fundamentals!

在交互式课程中回答

Recap: API Gateway Power

Great job! In this lesson, we explored the crucial role of an API Gateway in a microservices environment, specifically using Spring Cloud Gateway.

  • We understood its purpose as a single entry point.
  • Learned to configure basic routing with predicates.
  • Discovered how filters can modify requests and responses.
  • Touched upon its importance in centralizing security.

API Gateways are essential for building robust, secure, and manageable microservice systems.

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常见问题解答

「使用 Spring Cloud Gateway 构建 API 网关」课时是免费的吗？

是的 — 「使用 Spring Cloud Gateway 构建 API 网关」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Spring Boot 4 Microservices & REST APIs 课程的其余内容，请升级到 CoddyKit PRO。 Spring Boot 4 Microservices & REST APIs 课程共包含 3 节课。

「使用 Spring Cloud Gateway 构建 API 网关」这节课中我会学到什么？

设置 Spring Cloud Gateway 来路由请求、应用过滤器并保护您的微服务。 你通过在浏览器中直接运行的动手代码来练习 Spring Boot 4 Microservices & REST APIs，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Spring Boot 4 Microservices & REST APIs 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Spring Boot 4 Microservices & REST APIs 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 3 节课，共 3 节。

「使用 Spring Cloud Gateway 构建 API 网关」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Spring Boot 4 Microservices & REST APIs 课中编写并运行代码吗？

能。每节 Spring Boot 4 Microservices & REST APIs 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

  1. 实现 Eureka 服务发现
  2. 使用 Ribbon 实现客户端负载均衡
  3. 使用 Spring Cloud Gateway 构建 API 网关
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