Spring Boot 4 Microservices & REST APIs · レッスン

Spring Cloud GatewayによるAPIゲートウェイ

Spring Cloud Gatewayを設定し、リクエストのルーティング、フィルタの適用、マイクロサービスの保護を行います。

「Spring Cloud GatewayによるAPIゲートウェイ」はCoddyKit上の無料Spring Boot 4 Microservices & REST APIsレッスンです。これはレッスン3/3です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはSpring Boot 4 Microservices & REST APIs学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Spring Boot 4 Microservices & REST APIsコースには全3レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

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!

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.

よくある質問

「Spring Cloud GatewayによるAPIゲートウェイ」レッスンは無料ですか？

はい。「Spring Cloud GatewayによるAPIゲートウェイ」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Spring Boot 4 Microservices & REST APIsコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Spring Boot 4 Microservices & REST APIsコースには全3レッスンが含まれています。

「Spring Cloud GatewayによるAPIゲートウェイ」で何を学びますか？

Spring Cloud Gatewayを設定し、リクエストのルーティング、フィルタの適用、マイクロサービスの保護を行います。ブラウザで直接実行するハンズオンコードでSpring Boot 4 Microservices & REST APIsを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Spring Boot 4 Microservices & REST APIsを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのSpring Boot 4 Microservices & REST APIsは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン3/3です。

「Spring Cloud GatewayによるAPIゲートウェイ」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このSpring Boot 4 Microservices & REST APIsレッスンでコードを書いて実行できますか？

はい。すべてのSpring Boot 4 Microservices & REST APIsレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

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