导包：
org.springframework.boot:spring-boot-starter-data-mongodb:2.6.7
org.springframework.boot:spring-boot-starter-validation:2.6.7

框架中使用jpa+mongodb,这里记录两种方法操作mongodb，一个是使用mongoTemplate:

实体类：

public abstract class BaseDocument {
  @CreatedDate public Date createDate = new Date();

  @CreatedBy public String createdBy;

  @LastModifiedDate public Date lastModifiedDate = new Date();

  @LastModifiedBy public String lastModifiedBy;
}

@EqualsAndHashCode(callSuper = true)
@Document
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
@Slf4j
public class Event extends BaseDocument {

  @MongoId(value = FieldType.OBJECT_ID)
  private String id;

  @Indexed private String hostId;

  @Pattern(regexp = "^$|^.{4,255}$", message = "title must be in 5~255 characters")
  private String title;

  @Pattern(regexp = "^$|^[\\w\\W]{4,12225}$", message = "description must be in 5~12225 characters")
  private String description;
  }

使用mongoRepository的方法:

public interface EventRepository extends MongoRepository<Event, String>, EventRepositoryCustom {

  Optional<Event> findById(String eventId);

  void removeById(String eventId);
}

如果是一些复杂的情况如聚合，则需要自己写聚合语句：
例如：

  @Aggregation(
      pipeline = {
        "          {\n"
            + "        $match: {hostId: \"?0\", status: {$in:  ['STARTED','APPROVED']}}},\n"
            + "    },",
        "         {\n"
            + "        $addFields: {\n"
            + "            statusIndex: {\n"
            + "                            $cond: [\n"
            + "                                    { $eq: [\"$event.status\", \"STARTED\"] },\n"
            + "                                    0,\n"
            + "                                    {\n"
            + "                                        $cond: [{$or: [{ $eq: [\"$event.status\","
            + " \"COMMITTED\"] },{ $eq: [\"$event.status\", \"REVIEWING\"] }]}, 1, \n"
            + "                                        {$cond: [{ $eq: [\"$event.status\","
            + " \"APPROVED\"] }, 2, 3]}\n"
            + "                                        ],\n"
            + "                                    },\n"
            + "                                   ]\n"
            + "                          }\n"
            + "                            \n"
            + "                     }\n"
            + "    },",
        "           {\n"
            + "        $sort: {\n"
            + "            statusIndex: 1,\n"
            + "            actualEndDate: -1,\n"
            + "            planStartDate: -1\n"
            + "        }\n"
            + "    },",
        "          {\n" + "        $skip: ?1\n" + "    },",
        "          {\n" + "        $limit: ?2\n" + "    },"
      })
  List<Event> findByHostIdOrderCustom(String hostId, Integer skip, Integer limit);

关于聚合：
文档进入多阶段管道，将文档转换为聚合结果。例如：
在这个例子中：

db.orders.aggregate([
   { $match: { status: "A" } },
   { $group: { _id: "$cust_id", total: { $sum: "$amount" } } }
])

第一阶段：$match阶段按status字段过滤文档，并将status等于"A"的文档传递到下一阶段。
第二阶段：$group阶段按cust_id字段将文档分组，以计算每个唯一值cust_id的金额总和。
最基本的管道阶段提供_过滤器_，其操作类似于查询和修改输出文档格式的_文档转换_。

使用mongoTemplate：

  @Override
  public Long deleteReplyById(String commentId, String replyId, String userId) {
    Query query =
        Query.query(Criteria.where("replies.id").is(replyId))
            .addCriteria(Criteria.where("id").is(commentId));
    Update update =
        new Update().set("replies.$.deleteDate", new Date()).set("replies.$.deleteBy", userId);
    UpdateResult result = mongoTemplate.updateFirst(query, update, EventComment.class);
    return result.getModifiedCount();
  }

其他的一些数据库操作：

User user = new User();
user.setId("12345");
user.setName("admin");
user.setAddress("测试");

Query query = Query.query(Criteria.where("_id").is("5d1312aeb1829c279c6c256b"));
Update update = Update.update("name","zs");
//  更新一条数据
mongoTemplate.updateFirst(query,update, User.class);
mongoTemplate.updateFirst(query,update, "mongodb_user");
mongoTemplate.updateFirst(query,update, User.class,"mongodb_user");
//  更新多条数据
mongoTemplate.updateMulti(query,update, User.class);
mongoTemplate.updateMulti(query,update,"mongodb_user");
mongoTemplate.updateMulti(query,update, User.class,"mongodb_user");
//  更新数据，如果数据不存在就新增
mongoTemplate.upsert(query,update, User.class);
mongoTemplate.upsert(query,update,"mongodb_user");
mongoTemplate.upsert(query,update, User.class,"mongodb_user");