Spring Boot集成R2DBC实现响应式数据库访问

1. 添加依赖

在 pom.xml 文件中添加以下依赖：

<dependencies>
    <!-- Spring Boot WebFlux -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webflux</artifactId>
    </dependency>
    <!-- Spring Data R2DBC -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-r2dbc</artifactId>
    </dependency>
    <!-- R2DBC 驱动（以 PostgreSQL 为例） -->
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>r2dbc-postgresql</artifactId>
    </dependency>
    <!-- 测试相关依赖 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>io.projectreactor</groupId>
        <artifactId>reactor-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

2. 配置数据库连接

在 application.properties 或 application.yml 文件中配置数据库连接信息：

spring.r2dbc.url=r2dbc:postgresql://<db_url>:<port>/<db_name>
spring.r2dbc.username=<username>
spring.r2dbc.password=<password>

3. 创建实体类和仓库接口

创建一个实体类（如 User），并使用 @Table 注解标记：

import org.springframework.data.annotation.Id;
import org.springframework.data.relational.core.mapping.Table;

@Table("users")
public class User {
    @Id
    private Long id;
    private String name;
    private String email;
    // 省略 getter 和 setter 方法
}

然后创建一个仓库接口，继承 ReactiveCrudRepository：

java复制

import org.springframework.data.repository.reactive.ReactiveCrudRepository;

public interface UserRepository extends ReactiveCrudRepository<User, Long> {
}

4. 创建服务层和控制器

在服务层中注入 UserRepository，并实现业务逻辑：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;

    public Flux<User> getAllUsers() {
        return userRepository.findAll();
    }

    public Mono<User> createUser(User user) {
        return userRepository.save(user);
    }

    public Mono<User> updateUser(Long id, User user) {
        return userRepository.findById(id)
                .flatMap(existingUser -> {
                    existingUser.setName(user.getName());
                    existingUser.setEmail(user.getEmail());
                    return userRepository.save(existingUser);
                });
    }

    public Mono<Void> deleteUser(Long id) {
        return userRepository.deleteById(id);
    }
}

在控制器中定义 REST API：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@RestController
@RequestMapping("/users")
public class UserController {
    @Autowired
    private UserService userService;

    @GetMapping
    public Flux<User> getAllUsers() {
        return userService.getAllUsers();
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Mono<User> createUser(@RequestBody User user) {
        return userService.createUser(user);
    }

    @PutMapping("/{id}")
    public Mono<ResponseEntity<User>> updateUser(@PathVariable Long id, @RequestBody User user) {
        return userService.updateUser(id, user)
                .map(ResponseEntity::ok)
                .defaultIfEmpty(ResponseEntity.notFound().build());
    }

    @DeleteMapping("/{id}")
    public Mono<ResponseEntity<Void>> deleteUser(@PathVariable Long id) {
        return userService.deleteUser(id)
                .then(Mono.just(ResponseEntity.ok().<Void>build()))
                .defaultIfEmpty(ResponseEntity.notFound().build());
    }
}

5. 启动类

在主类上添加 @EnableR2dbcRepositories 注解以启用 R2DBC 仓库支持：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;

@SpringBootApplication
@EnableR2dbcRepositories
public class SpringReactiveR2DbcApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringReactiveR2DbcApplication.class, args);
    }
}

6. 运行应用

启动应用后，访问 /users 等接口即可测试响应式数据库操作。