Spring 学习笔记 01：IoC、依赖注入与第一个 Spring Boot 应用

public class BookService {

    private final BookRepository repository = new MysqlBookRepository();

    public Book findById(Long id) {
        return repository.findById(id).orElseThrow();
    }
}

library/
├── mvnw / mvnw.cmd
├── pom.xml
└── src
    ├── main
    │   ├── java/com/example/library/
    │   │   ├── LibraryApplication.java              ← 主类
    │   │   ├── config/
    │   │   │   ├── AppConfig.java                   ← @Bean 声明（第 01 篇）
    │   │   │   ├── DataInitializer.java             ← CommandLineRunner 灌数据（第 02 篇）
    │   │   │   ├── WebConfig.java                   ← 拦截器与语言解析器（第 07、09 篇）
    │   │   │   └── WhitelistLocaleResolver.java     ← 语言白名单（第 07 篇）
    │   │   ├── domain/
    │   │   │   ├── Book.java / BookStatus.java      ← 实体（第 02、04 篇）
    │   │   │   ├── Category.java / Tag.java         ← 关联实体（第 04 篇）
    │   │   │   ├── Member.java / Loan.java          ← 借阅（第 10 篇）
    │   │   │   └── User.java / UserRole.java        ← 登录用户（第 08 篇）
    │   │   ├── dto/
    │   │   │   ├── BookForm.java / BookDraft.java   ← 表单对象（第 06、08 篇）
    │   │   │   ├── BookResponse.java / BookTitleDto.java ← 对外表示（第 03、11 篇）
    │   │   ├── repository/                          ← 第 02–04 篇
    │   │   │   ├── BookRepository.java / BookSummary.java
    │   │   │   ├── CategoryRepository.java / TagRepository.java
    │   │   │   └── MemberRepository.java / LoanRepository.java / UserRepository.java
    │   │   ├── service/                             ← 第 02、03、08、10 篇
    │   │   ├── validation/                          ← 自定义校验（第 06 篇）
    │   │   └── web/                                 ← 第 05、06、08、09、11、12 篇
    │   │       ├── BookViewController.java / BookController.java
    │   │       ├── AccountController.java / BookWizardController.java
    │   │       ├── GlobalExceptionHandler.java / ApiExceptionHandler.java
    │   │       ├── RequireAdmin.java
    │   │       ├── interceptor/                     ← 第 09 篇
    │   │       └── filter/                          ← 第 09 篇
    │   └── resources/
    │       ├── application.properties / application-mysql.properties
    │       ├── messages.properties / messages_en.properties   ← 第 07 篇
    │       └── templates/                           ← 第 05–08 篇
    └── test/java/com/example/library/
        ├── MockitoSmokeTest.java                    ← 环境自检
        ├── repository/BookRepositoryTest.java       ← @DataJpaTest（第 04 篇）
        ├── service/LoanServiceTransactionTest.java  ← 事务回滚（第 10 篇）
        └── web/BookControllerTest.java / BookControllerSliceTest.java ← 第 11、12 篇

./mvnw spring-boot:run     # 启动，默认用 H2 内存库
./mvnw test                # 编译 + 跑测试

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <argLine>-Djdk.attach.allowAttachSelf=true</argLine>
    </configuration>
</plugin>

package com.example.library.service;

import com.example.library.repository.BookRepository;
import org.springframework.stereotype.Service;

@Service
public class BookService {

    private final BookRepository repository;

    // 只有一个构造器时，@Autowired 可以省略
    public BookService(BookRepository repository) {
        this.repository = repository;
    }
}

package com.example.library.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.time.Clock;

@Configuration
public class AppConfig {

    @Bean
    public Clock clock() {
        return Clock.systemDefaultZone();
    }
}

library/
├── mvnw / mvnw.cmd              ← Maven Wrapper，没装 Maven 也能构建
├── pom.xml                      ← 构建与依赖描述
├── src
│   ├── main
│   │   ├── java/com/example/library/
│   │   │   └── LibraryApplication.java    ← 主类
│   │   └── resources/
│   │       └── application.properties     ← 配置写在这里
│   └── test/java/com/example/library/
│       └── LibraryApplicationTests.java
└── target/                      ← 构建产物（默认不进版本库）

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>4.1.1</version>
    <relativePath/>
</parent>

<properties>
    <java.version>17</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webmvc</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webmvc-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

package com.example.library;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class LibraryApplication {

    public static void main(String[] args) {
        SpringApplication.run(LibraryApplication.class, args);
    }
}

package com.example.library.domain;

public record Book(Long id, String title, String author) {
}

package com.example.library.repository;

import com.example.library.domain.Book;
import org.springframework.stereotype.Repository;

import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;

@Repository
public class InMemoryBookRepository {

    private final Map<Long, Book> books = new ConcurrentHashMap<>();
    private final AtomicLong sequencer = new AtomicLong();

    public Book save(String title, String author) {
        long id = sequencer.incrementAndGet();
        Book book = new Book(id, title, author);
        books.put(id, book);
        return book;
    }

    public Optional<Book> findById(Long id) {
        return Optional.ofNullable(books.get(id));
    }

    public List<Book> findAll() {
        return List.copyOf(books.values());
    }
}

package com.example.library.service;

import com.example.library.domain.Book;

import java.util.List;

public interface BookService {

    Book add(String title, String author);

    Book findById(Long id);

    List<Book> findAll();
}

package com.example.library.service;

import com.example.library.domain.Book;
import com.example.library.repository.InMemoryBookRepository;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.NoSuchElementException;

@Service
public class BookServiceImpl implements BookService {

    private final InMemoryBookRepository repository;

    public BookServiceImpl(InMemoryBookRepository repository) {
        this.repository = repository;
    }

    @Override
    public Book add(String title, String author) {
        return repository.save(title, author);
    }

    @Override
    public Book findById(Long id) {
        return repository.findById(id)
                .orElseThrow(() -> new NoSuchElementException("找不到图书：" + id));
    }

    @Override
    public List<Book> findAll() {
        return repository.findAll();
    }
}

package com.example.library.web;

import com.example.library.domain.Book;
import com.example.library.service.BookService;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/api/books")
public class BookController {

    private final BookService bookService;

    public BookController(BookService bookService) {
        this.bookService = bookService;
    }

    @GetMapping
    public List<Book> list() {
        return bookService.findAll();
    }

    @GetMapping("/{id}")
    public Book get(@PathVariable Long id) {
        return bookService.findById(id);
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Book add(@RequestBody CreateBookRequest request) {
        return bookService.add(request.title(), request.author());
    }

    public record CreateBookRequest(String title, String author) {
    }
}

./mvnw spring-boot:run

curl -X POST http://localhost:8080/api/books \
  -H "Content-Type: application/json" \
  -d '{"title":"重构","author":"Martin Fowler"}'

curl http://localhost:8080/api/books

Invoke-RestMethod -Method Post http://localhost:8080/api/books `
  -ContentType "application/json; charset=utf-8" `
  -Body '{"title":"\u91cd\u6784","author":"Martin Fowler"}'

Invoke-RestMethod http://localhost:8080/api/books

[{ "id": 1, "title": "重构", "author": "Martin Fowler" }]

# application.properties
debug=true