总结

听说MongoDB官方的Rust驱动程序（alpha版）已经发布了，所以我决定试一试。
虽然买了关于Rust的书籍，但一直没时间读，所以我从安装开始，花了大约半天的时间学习了用Rust编写MongoDB驱动所需的基本知识。在进行试验和纠错的同时，我也在写这篇文章，所以可能会有一些错误。希望借此机会能够真正开始学习Rust。

环境

• Windows 10

• MongoDB Community版 4.2.2

• rust 1.40.0

• MongoDB rust

ドライバー 0.9.0 (alpha版)

https://crates.io/crates/mongodb
https://github.com/mongodb/mongo-rust-driver

bson 0.14.0

https://crates.io/crates/bson
https://github.com/mongodb/bson-rust

实施

在Cargo.toml中添加依赖项

[dependencies]

mongodb ="0.9.0"
bson = "0.14.0"

尝试运行文件中列出的代码。

use mongodb::{error::Result, options::{ClientOptions, FindOptions}, Client};
use bson::{doc, bson, Bson};

fn main() {
    let client = connect_mongo().expect("failed to connect");
    list_db(&client).expect("failed to list db names");
    list_collection(&client, "test").expect("failed to list collection names");
    insert_docs(&client).expect("failed to insert docs");
    find_docs(&client).expect("failed to find docs");
}

fn connect_mongo() -> Result<Client> {
    // Parse a connection string into an options struct.
    let mut client_options = ClientOptions::parse("mongodb://localhost:27017")?;

    // Manually set an option.
    client_options.app_name = Some("My App".to_string());

    // Get a handle to the deployment.
    let client = Client::with_options(client_options)?;
    Ok(client)
}

fn list_db(client: &Client) -> Result<()> {
    // List the names of the databases in that deployment.
    println!("------ print db --------");
    for db_name in client.list_database_names(None)? {
        println!("{}", db_name);
    }
    Ok(())
}

fn list_collection(client: &Client, dbname: &str) -> Result<()> {
    // Get a handle to a database.
    let db = client.database(dbname);

    // List the names of the collections in that database.
    println!("------ print collection ({}) --------", dbname);
    for collection_name in db.list_collection_names(None)? {
        println!("{}", collection_name);
    }
    Ok(())
}

fn insert_docs(client: &Client) -> Result<()> {
    // Get a handle to a collection in the database.
    let collection = client.database("test").collection("books");

    let docs = vec![
        doc! { "title": "1984", "author": "George Orwell" },
        doc! { "title": "Animal Farm", "author": "George Orwell" },
        doc! { "title": "The Great Gatsby", "author": "F. Scott Fitzgerald" },
    ];

    // Insert some documents into the "test.books" collection.
    collection.insert_many(docs, None)?;

    Ok(())
}

fn find_docs(client: &Client) -> Result<()> {
    // Get a handle to a collection in the database.
    let collection = client.database("test").collection("books");
    // Query the documents in the collection with a filter and an option.
    let filter = doc! { "author": "George Orwell" };
    let find_options = FindOptions::builder().sort(doc! { "title": 1 }).build();
    let cursor = collection.find(filter, find_options)?;

    println!("------ print find  --------");
    // Iterate over the results of the cursor.
    for result in cursor {
        match result {
            Ok(document) => {
                if let Some(title) = document.get("title").and_then(Bson::as_str) {
                    println!("title: {}", title);
                }  else {
                    println!("no title found");
                }
            }
            Err(e) => return Err(e.into()),
        }
    }

    Ok(())
}

> cargo run
     Running `target\debug\mongorust.exe`
------ print db --------
admin
config
local
test
------ print collection (test) --------
col
system.profile
books
col2
------ print find  --------
title: 1984
title: Animal Farm

最终

我最初以为只要复制粘贴代码就可以立即运行，但我对?运算符、Result的使用以及client变量的所有权不太了解，所以花了很长时间。由于没有处理结构体的示例，所以我会继续研究。

链接

使用MongoDB官方的Rust驱动程序（Alpha版本）进行尝试（2）（使用结构体）。