[][src]Crate bson

BSON, short for Binary JSON, is a binary-encoded serialization of JSON-like documents. Like JSON, BSON supports the embedding of documents and arrays within other documents and arrays. BSON also contains extensions that allow representation of data types that are not part of the JSON spec. For example, BSON has a datetime type and a binary data type.

// JSON equivalent
{"hello": "world"}

// BSON encoding
\x16\x00\x00\x00                   // total document size
\x02                               // 0x02 = type String
hello\x00                          // field name
\x06\x00\x00\x00world\x00          // field value
\x00                               // 0x00 = type EOO ('end of object')

BSON is the primary data representation for MongoDB, and this crate is used in the mongodb driver crate in its API and implementation.

For more information about BSON itself, see bsonspec.org.

BSON values

Many different types can be represented as a BSON value, including 32-bit and 64-bit signed integers, 64 bit floating point numbers, strings, datetimes, embedded documents, and more. To see a full list of possible BSON values, see the BSON specification. The various possible BSON values are modeled in this crate by the Bson enum.

Creating Bson instances

Bson values can be instantiated directly or via the bson! macro:

let string = Bson::String("hello world".to_string());
let int = Bson::Int32(5);
let array = Bson::Array(vec![Bson::Int32(5), Bson::Boolean(false)]);

let string: Bson = "hello world".into();
let int: Bson = 5i32.into();

let string = bson!("hello world");
let int = bson!(5);
let array = bson!([5, false]);

bson! has supports both array and object literals, and it automatically converts any values specified to Bson, provided they are Into<Bson>.

Bson value unwrapping

Bson has a number of helper methods for accessing the underlying native Rust types. These helpers can be useful in circumstances in which the specific type of a BSON value is known ahead of time.


let value = Bson::Int32(5);
let int = value.as_i32(); // Some(5)
let bool = value.as_bool(); // None

let value = bson!([true]);
let array = value.as_array(); // Some(&Vec<Bson>)

BSON documents

BSON documents are ordered maps of UTF-8 encoded strings to BSON values. They are logically similar to JSON objects in that they can contain subdocuments, arrays, and values of several different types. This crate models BSON documents via the Document struct.

Creating Documents

Documents can be created directly either from a byte reader containing BSON data or via the doc! macro:

let mut bytes = hex::decode("0C0000001069000100000000").unwrap();
let doc = Document::from_reader(&mut bytes.as_slice()).unwrap(); // { "i": 1 }

let doc = doc! {
   "hello": "world",
   "int": 5,
   "subdoc": { "cat": true },

doc! works similarly to bson!, except that it always returns a Document rather than a Bson.

Document member access

Document has a number of methods on it to facilitate member access:

let doc = doc! {
   "string": "string",
   "bool": true,
   "i32": 5,
   "doc": { "x": true },

// attempt get values as untyped Bson
let none = doc.get("asdfadsf"); // None
let value = doc.get("string"); // Some(&Bson::String("string"))

// attempt to get values with explicit typing
let string = doc.get_str("string"); // Ok("string")
let subdoc = doc.get_document("doc"); // Some(Document({ "x": true }))
let error = doc.get_i64("i32"); // Err(...)

Modeling BSON with strongly typed data structures

While it is possible to work with documents and BSON values directly, it will often introduce a lot of boilerplate for verifying the necessary keys are present and their values are the correct types. serde provides a powerful way of mapping BSON data into Rust data structures largely automatically, removing the need for all that boilerplate.


#[derive(Serialize, Deserialize)]
struct Person {
    name: String,
    age: u8,
    phones: Vec<String>,

fn typed_example() {
    // Some BSON input data as a `Bson`.
    let bson_data: Bson = bson!({
        "name": "John Doe",
        "age": 43,
        "phones": [
            "+44 1234567",
            "+44 2345678"

    // Deserialize the Person struct from the BSON data, automatically
    // verifying that the necessary keys are present and that they are of
    // the correct types.
    let mut person: Person = bson::from_bson(bson_data).unwrap();

    // Do things just like with any other Rust data structure.
    println!("Redacting {}'s record.", person.name);
    person.name = "REDACTED".to_string();

    // Get a serialized version of the input data as a `Bson`.
    let redacted_bson = bson::to_bson(&person).unwrap();

Any types that implement Serialize and Deserialize can be used in this way. Doing so helps separate the "business logic" that operates over the data from the (de)serialization logic that translates the data to/from its serialized form. This can lead to more clear and concise code that is also less error prone.


pub use self::bson::Document;
pub use self::de::from_bson;
pub use self::decimal128::Decimal128;
pub use self::ser::to_bson;



Backward compatibility




BSON Decimal128 data type representation


A BSON document represented as an associative HashMap with insertion ordering.


Deserialization and serialization of MongoDB Extended JSON v2






Constants derived from the BSON Specification Version 1.1.



Construct a bson::BSON value from a literal.


Construct a bson::Document value.



Represents a BSON binary value.


DateTime representation in struct for serde serialization


Represents a DBPointer. (Deprecated)


Serde Deserializer


Represents a BSON code with scope value.


Represents a BSON regular expression value.


Serde Serializer


Represents a BSON timestamp value.



Possible BSON value types.

Type Definitions


Alias for Vec<Bson>.