spring data 连接mongodb的两种方式

以Spring Boot为例，连接MongoDB有两种主要方式：使用MongoTemplate或使用MongoRepository。

使用MongoTemplate

1. 添加MongoDB和Spring Data MongoDB依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-mongodb</artifactId>
</dependency>

1. 在application.properties中添加数据库配置

spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.authentication-database=admin
spring.data.mongodb.username=yourusername
spring.data.mongodb.password=yourpassword
spring.data.mongodb.database=yourdbname

1. 创建实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
@Document(collection = "users")
public class User {
    @Id
    private String id;
    private String name;
    private Integer age;
}

1. 创建MongoTemplate

@Configuration
public class MongoConfig {
    @Autowired
    private MongoClient mongoClient;

    @Bean
    public MongoTemplate mongoTemplate() {
        return new MongoTemplate(mongoClient, "yourdbname");
    }
}

1. 在service/dao层使用MongoTemplate

@Service
public class UserService {
    @Autowired
    private MongoTemplate mongoTemplate;

    public void saveUser(User user) {
        mongoTemplate.save(user);
    }

    public User getUser(String id) {
        Query query = Query.query(Criteria.where("_id").is(id));
        return mongoTemplate.findOne(query, User.class);
    }

    public void updateUser(User user) {
        Query query = Query.query(Criteria.where("_id").is(user.getId()));
        Update update = new Update();
        update.set("name", user.getName());
        update.set("age", user.getAge());
        mongoTemplate.updateFirst(query, update, User.class);
    }

    public void deleteUser(String id) {
        Query query = Query.query(Criteria.where("_id").is(id));
        mongoTemplate.remove(query, User.class);
    }
}

使用MongoRepository

1. 添加MongoDB和Spring Data MongoDB依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-mongodb</artifactId>
</dependency>

1. 在application.properties中添加数据库配置

spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.authentication-database=admin
spring.data.mongodb.username=yourusername
spring.data.mongodb.password=yourpassword
spring.data.mongodb.database=yourdbname

1. 创建实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
@Document(collection = "users")
public class User {
    @Id
    private String id;
    private String name;
    private Integer age;
}

1. 创建MongoRepository

public interface UserRepository extends MongoRepository<User, String> {
    User findByName(String name);
}

1. 在service/dao层使用MongoRepository

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

    public void saveUser(User user) {
        userRepository.save(user);
    }

    public User getUser(String id) {
        return userRepository.findById(id).orElse(null);
    }

    public void updateUser(User user) {
        userRepository.save(user);
    }

    public void deleteUser(String id) {
        userRepository.deleteById(id);
    }
}

以上就是使用MongoTemplate和MongoRepository两种方式连接MongoDB的完整攻略。

示例：实现一个简单的用户登录和注册功能

1. 创建UserController，添加REST接口

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

    @PostMapping("/register")
    public String register(@RequestBody User user) {
        if (userService.getUserByName(user.getName()) != null) {
            return "用户名已存在";
        } else {
            userService.saveUser(user);
            return "注册成功";
        }
    }

    @PostMapping("/login")
    public String login(@RequestBody User user) {
        User foundUser = userService.getUserByName(user.getName());
        if (foundUser == null) {
            return "用户不存在";
        } else if (foundUser.getPassword().equals(user.getPassword())) {
            return "登录成功";
        } else {
            return "密码错误";
        }
    }
}

1. 修改UserService，添加getUserByName方法

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

    public void saveUser(User user) {
        userRepository.save(user);
    }

    public User getUserById(String id) {
        return userRepository.findById(id).orElse(null);
    }

    public User getUserByName(String name) {
        return userRepository.findByName(name);
    }

    public void updateUser(User user) {
        userRepository.save(user);
    }

    public void deleteUser(String id) {
        userRepository.deleteById(id);
    }
}

1. 修改User实体类，添加password属性

@Data
@AllArgsConstructor
@NoArgsConstructor
@Document(collection = "users")
public class User {
    @Id
    private String id;
    private String name;
    private Integer age;
    private String password;
}

1. 注册新用户

POST /user/register HTTP/1.1
Content-Type: application/json

{
    "name": "test",
    "age": 18,
    "password": "123456"
}

1. 登录已存在的用户

POST /user/login HTTP/1.1
Content-Type: application/json

{
    "name": "test",
    "password": "123456"
}