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

import org.springframework.data.mongodb.MongoDbFactory;
import com.mongodb.DB;
@Component
public class MyBean {
  private final MongoDbFactory mongo;
  @Autowired
  public MyBean(MongoDbFactory mongo) {
    this.mongo = mongo;
  }
  // ...
  public void example() {
  DB db = mongo.getDb();
    // ...
  }
}

spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
  private final MongoTemplate mongoTemplate;
  
  @Autowired
  public MyBean(MongoTemplate mongoTemplate) {
    this.mongoTemplate = mongoTemplate;
  }
  // ...
}

spring.data.mongodb.uri=mongodb://name:pass@localhost:27017/test

spring.data.mongodb.uri=mongodb://user:pass@ip1:port1,ip2:port2/database

public class UserInfo implements Serializable {
  private Long id;
  private String userName;
  private String passWord;
  //getter、setter省略
}

@Component
public class UserInfoDaoImpl implements UserInfoDao {// UserInfoDao 自定义接口
  @Autowired
  private MongoTemplate mongoTemplate;
  /**
   * 创建对象
   * @param user
   */
  @Override
  public void saveUser(UserInfo user) {
    mongoTemplate.save(user);
  }
  /**
   * 根据用户名查询对象
   * @param userName
   * @return
   */
  @Override
  public UserInfo findUserByUserName(String userName) {
    Query query=new Query(Criteria.where("userName").is(userName));
    UserInfo user = mongoTemplate.findOne(query , UserInfo.class);
    return user;
  }
  /**
   * 更新对象
   * @param user
   */
  @Override
  public void updateUser(UserInfo user) {
    Query query=new Query(Criteria.where("id").is(user.getId()));
    Update update= new Update().set("userName", user.getUserName()).set("passWord", user.getPassWord());
    //更新查询返回结果集的第一条
    mongoTemplate.updateFirst(query,update,UserInfo.class);
    //更新查询返回结果集的所有
    // mongoTemplate.updateMulti(query,update,UserInfo.class);
  }
  /**
   * 删除对象
   * @param id
   */
  @Override
  public void deleteUserById(Long id) {
    Query query=new Query(Criteria.where("id").is(id));
    mongoTemplate.remove(query,UserInfo.class);
  }
}

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserDaoTest {
  @Autowired
  private UserDao userDao;
  @Test
  public void testSaveUser() throws Exception {
    UserInfo user=new UserInfo();
    user.setId(2);
    user.setUserName("路人甲");
    user.setPassWord("123456");
    userDao.saveUser(user);
  }
  @Test
  public void findUserByUserName(){
    UserInfo user= userDao.findUserByUserName("路人甲");
    System.out.println("user is "+user);
  }
  @Test
  public void updateUser(){
    UserInfo user=new UserInfo();
    user.setId(3);
    user.setUserName("路人乙");
    user.setPassWord("123456");
    userDao.updateUser(user);
  }
  @Test
  public void deleteUserById(){
    userDao.deleteUserById(3);
  }
}