MongoDB 查询数据

查询全部数据

通过 find() 方法，可以对数据进行查询，它的参数：

• filter 是一个 Document 结构体
  • 可以通过 mongodb::bson::doc! 宏（它其实是重新导出的 bson::doc!）快速构建
  • 它用于指定过滤条件，通过传递一个空的过滤条件，即 doc!{} 可以实现查询全部数据

它的返回值是 Find 结构体，该结构体中包含诸多额外操作，比如排序：

• sort()：排序，它的参数也是一个 Document
  • 语法：{字段名:值}
  • 取值：
    • -1：降序
    • 1：升序

下一小节我们将对其进行更进一步地说明。

测试：

结果：

HTTP/1.1 200 OK
content-type: application/json
content-length: 483
connection: close
date: Wed, 04 Jun 2025 12:38:41 GMT

[
  {
    "_id": "d100i1kdrfaihab7dmjg",
    "title": "note3",
    "content": "笔记3",
    "created_at": {
      "$date": {
        "$numberLong": "1749027078627"
      }
    }
  },
  {
    "_id": "d100i1kdrfaihab7dmj0",
    "title": "note2",
    "content": "笔记2",
    "created_at": {
      "$date": {
        "$numberLong": "1749027078627"
      }
    }
  },
  {
    "_id": "d100i1kdrfaihab7dmig",
    "title": "note1",
    "content": "笔记1",
    "created_at": {
      "$date": {
        "$numberLong": "1749027078627"
      }
    }
  },
  {
    "_id": "d100fo4drfai1th323sg",
    "title": "foo",
    "content": "bar",
    "created_at": {
      "$date": {
        "$numberLong": "1749026784227"
      }
    }
  }
]

分页查询全部数据

上一小节提到，find() 的返回值是一个 Find 结构体，它提供了一些额外操作：

• skip()：跳过指定记录数，它的参数是一个 u64 值，用于指定要跳过的记录数
• limit()：限定查询的记录数，它的参数是一个 i64 值，用于指定要限定的记录数

pub async fn list_pagination(
    State(state): State<ArcAppState>,
    Query(query): Query<PaginationRequest>,
) -> Result<Json<Vec<model::Note>>> {
    let mut notes = vec![];
    let mut cursor = state
        .note_collect()
        .find(doc! {})
        .sort(doc! { "_id": -1})
        .skip(query.offset() as u64)
        .limit(query.limit() as i64)
        .await?;
    while cursor.advance().await? {
        let n = cursor.deserialize_current()?;
        notes.push(n);
    }
    Ok(Json(notes))
}


#[derive(Deserialize)]
pub struct PaginationRequest {
    pub page: Option<u32>,
}
impl PaginationRequest {
    pub fn page(&self) -> u32 {
        self.page.unwrap_or(0)
    }

    pub fn limit(&self) -> u32 {
        3
    }
    pub fn offset(&self) -> u32 {
        self.page() * self.limit()
    }
}

测试：

## 分页显示笔记(无参数)
GET http://127.0.0.1:9527/pagination
Content-Type: application/json

## 分页显示笔记，显式第1页
GET http://127.0.0.1:9527/pagination?page=0
Content-Type: application/json

## 分页显示笔记，第2页
GET http://127.0.0.1:9527/pagination?page=1
Content-Type: application/json

结果：

HTTP/1.1 200 OK
content-type: application/json
content-length: 367
connection: close
date: Wed, 04 Jun 2025 12:37:38 GMT

[
  {
    "_id": "d100i1kdrfaihab7dmjg",
    "title": "note3",
    "content": "笔记3",
    "created_at": {
      "$date": {
        "$numberLong": "1749027078627"
      }
    }
  },
  {
    "_id": "d100i1kdrfaihab7dmj0",
    "title": "note2",
    "content": "笔记2",
    "created_at": {
      "$date": {
        "$numberLong": "1749027078627"
      }
    }
  },
  {
    "_id": "d100i1kdrfaihab7dmig",
    "title": "note1",
    "content": "笔记1",
    "created_at": {
      "$date": {
        "$numberLong": "1749027078627"
      }
    }
  }
]

--------------------------------------

HTTP/1.1 200 OK
content-type: application/json
content-length: 117
connection: close
date: Wed, 04 Jun 2025 12:37:58 GMT

[
  {
    "_id": "d100fo4drfai1th323sg",
    "title": "foo",
    "content": "bar",
    "created_at": {
      "$date": {
        "$numberLong": "1749026784227"
      }
    }
  }
]

查询单条

pub async fn get(
    State(state): State<ArcAppState>,
    Path(id): Path<String>,
) -> Result<Json<Option<model::Note>>> {
    let n = state.note_collect().find_one(doc! {"_id":&id}).await?;
    Ok(Json(n))
}

测试：

## 获取笔记
GET http://127.0.0.1:9527/d100i1kdrfaihab7dmjg
Content-Type: application/json

结果：

HTTP/1.1 200 OK
content-type: application/json
content-length: 121
connection: close
date: Fri, 06 Jun 2025 05:57:25 GMT

{
  "_id": "d100i1kdrfaihab7dmjg",
  "title": "note3",
  "content": "笔记3",
  "created_at": {
    "$date": {
      "$numberLong": "1749027078627"
    }
  }
}