Crate serde_dynamodb_streams

DynamoDB

In its low level API, DynamoDB works with JSON objects with extra levels to set the type of the values.

{
    "Item": {
        "Age": {"N": "8"},
        "Colors": {
            "L": [
                {"S": "White"},
                {"S": "Brown"},
                {"S": "Black"}
            ]
        },
        "Name": {"S": "Fido"},
        "Vaccinations": {
            "M": {
                "Rabies": {
                    "L": [
                        {"S": "2009-03-17"},
                        {"S": "2011-09-21"},
                        {"S": "2014-07-08"}
                    ]
                },
                "Distemper": {"S": "2015-10-13"}
            }
        },
        "Breed": {"S": "Beagle"},
        "AnimalType": {"S": "Dog"}
    }
}

The allowed type keys are described here.

Rusoto DynamoDB

Rusoto DynamoDB map those values to AttributeValue, and functions to get/set/… from DynamoDB use HashMap<String, AttributeValue> as a way to represent the data.

Parsing HashMap as strongly typed data structures

Serde provides a powerful way of mapping HashMap data into Rust data structures largely automatically by using serde_dynamodb_streams::from_hashmap

extern crate serde;
extern crate serde_dynamodb;

extern crate rusoto_core;
extern crate rusoto_dynamodb;

#[macro_use]
extern crate serde_derive;

use std::collections::HashMap;

use rusoto_core::Region;
use rusoto_dynamodb::{DynamoDb, DynamoDbClient, QueryInput, AttributeValue};

use serde_dynamodb_streams::Error;

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

fn typed_example() -> Result<(), Error> {

    let client = DynamoDbClient::simple(Region::UsEast1);

    let mut query = HashMap::new();
    query.insert(String::from(":surname"), AttributeValue {
        s: Some(String::from("Smith")),
        ..Default::default()
    });
    // get data from DynamoDB
    let persons: Vec<Person> = client
        .query(&QueryInput {
            table_name: String::from("person"),
            key_condition_expression: Some(String::from("surname = :surname")),
            expression_attribute_values: Some(query),
            ..Default::default()
        })
        .sync()
        .unwrap()
        .items
        .unwrap_or_else(|| vec![])
        .into_iter()
        .map(|item| serde_dynamodb_streams::from_hashmap(item).unwrap())
        .collect();


    // Do things just like with any other Rust data structure.
    for p in persons {
        println!("Please call {} at the number {}", p.surname, p.phones[0]);
    }

    Ok(())
}

Creating an HashMap by serializing data structures

A data structure can be converted to an HashMap by serde_dynamodb_streams::to_hashmap.

use serde::{Serialize, Deserialize};
use serde_dynamodb_streams::Error;

#[derive(Serialize, Deserialize, Debug)]
struct Address {
    street: String,
    city: String,
}

fn print_an_address() -> Result<(), Error> {
    // Some data structure.
    let address = Address {
        street: "10 Downing Street".to_owned(),
        city: "London".to_owned(),
    };

    // Serialize it to an HashMap.
    let dynamodb_object = serde_dynamodb_streams::to_hashmap(&address)?;

    // Print, write to a file, or send to an HTTP server.
    println!("{:?}", dynamodb_object);

    Ok(())
}

Features

rusoto_dynamodb

Feature rusoto_dynamodb is enabled by default and add methods serde_dynamodb_streams::from_hashmap and serde_dynamodb_streams::to_hashmap. Those methods work with AttributeValue from DynamoDB.

rusoto_dynamodbstreams

Feature rusoto_dynamodbstreams is disabled by default and add module streams with methods serde_dynamodb_streams::streams::from_hashmap and serde_dynamodb_streams::streams::to_hashmap. Those methods work with AttributeValue from DynamoDB Streams.

Re-exports

pub use error::Error;

Modules

error	This type represents all possible errors that can occur when serializing or deserializing DynamoDB data.
streams	Methods in this module are generated to work with AttributeValue from DynamoDB Streams instead of AttributeValue from DynamoDB.