使用Spring Cache优化数据库访问

在这篇博客中，我们将学习如何使用Spring Cache来优化数据库访问，提高系统性能。我们将创建一个简单的图书管理应用作为示例，并演示如何通过缓存减少对数据库的频繁查询。

1. 项目结构

首先，我们看一下项目的基本结构：

lfsun-study-cacheable
|-- src
|   |-- main
|       |-- java
|           |-- com.lfsun.cacheable
|               |-- controller
|                   |-- BookController.java
|               |-- dao
|                   |-- BookRepository.java
|               |-- entity
|                   |-- Book.java
|               |-- service
|                   |-- BookService.java
|                   |-- impl
|                       |-- BookServiceImpl.java
|               |-- LfsunStudyCacheableApplication.java
|       |-- resources
|           |-- application.properties
|-- pom.xml

2. 项目依赖

我们使用了Spring Boot和Spring Data JPA来简化项目配置。以下是主要的Maven依赖：

<!-- Spring Boot Starter -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
</dependency>

<!-- Spring Boot Starter Test -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>

<!-- Spring Boot Starter Web -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<!-- Spring Boot Starter Data JPA -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<!-- Lombok for easy POJOs -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>

<!-- MySQL Connector -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.28</version>
</dependency>

3. 数据库配置

配置MySQL数据库连接信息和Hibernate方言：

spring.datasource.url=jdbc:mysql://localhost:3306/lfsun_study
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL8Dialect

4. 实体类

定义一个简单的实体类Book，用于表示图书信息：

@Entity
@Data
@Table(name = "cacheable_book")
public class Book implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String author;
}

5. 数据访问层

创建一个JPA Repository接口 BookRepository，用于数据库交互：

public interface BookRepository extends JpaRepository<Book, Long> {
    Book findByTitle(String title);
    void deleteByTitle(String title);
}

6. 服务层

实现一个 BookService 接口，并创建具体的服务实现 BookServiceImpl。在服务实现中，使用Spring Cache注解来优化数据库访问：

@Service
@AllArgsConstructor
public class BookServiceImpl implements BookService {

    private final BookRepository bookRepository;

    @Override
    @Cacheable(value = "books", key = "#title")
    public Book getByTitle(String title) {
        System.out.println("Getting book from database for title: " + title);
        return bookRepository.findByTitle(title);
    }

    @Override
    @CachePut(value = "books", key = "#result.title")
    public Book save(Book book) {
        System.out.println("Saving book to database: " + book.getTitle());
        return bookRepository.save(book);
    }

    @Override
    @Transactional
    @CacheEvict(value = "books", key = "#title")
    public void deleteByTitle(String title) {
        System.out.println("Deleting book from database for title: " + title);
        bookRepository.deleteByTitle(title);
    }
}

7. 控制器层

创建REST控制器 BookController 处理图书的获取、保存和删除操作：

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

    private final BookService bookService;

    @GetMapping("/{title}")
    public Book getBookByTitle(@PathVariable String title) {
        return bookService.getByTitle(title);
    }

    @PostMapping
    public Book saveBook(@RequestBody Book book) {
        return bookService.save(book);
    }

    @PostMapping("/delete/{title}")
    public ResponseEntity<String> deleteBookByTitle(@PathVariable String title) {
        bookService.deleteByTitle(title);
        return new ResponseEntity<>("Book deleted successfully", HttpStatus.OK);
    }
}

8. 主应用程序类

在主应用程序类 LfsunStudyCacheableApplication 上启用Spring缓存：

@SpringBootApplication
@EnableCaching
public class LfsunStudyCacheableApplication {

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

测试

1. 新增图书

POST http://localhost:8888/books
Content-Type: application/json

{
  "title": "JavaStudy777",
  "author": "冷风扇",
  "isbn": "1234567890"
}

2. 获取图书信息

# GET请求
GET http://localhost:8888/books/JavaStudy777

3. 删除图书

# POST请求
POST http://localhost:8888/books/delete/JavaStudy777