AWS SDK를 사용하고 If-Modified-Since 헤더를 지정하여 Amazon S3 버킷에서 객체 가져오기

다음 코드 예제는 S3 버킷이 마지막 검색 시간 이후 수정되지 않았을 때에 한하여 해당 버킷 내의 객체에서 데이터를 읽는 방법을 보여줍니다.

Rust

SDK for Rust

참고

GitHub에 더 많은 내용이 있습니다. AWS코드 예시 리포지토리에서 전체 예시를 찾고 설정 및 실행하는 방법을 배워보세요.

use aws_sdk_s3::{
    error::SdkError,
    operation::head_object::HeadObjectError,
    primitives::{ByteStream, DateTime, DateTimeFormat},
    Client, Error,
};
use tracing::{error, warn};

const KEY: &str = "key";
const BODY: &str = "Hello, world!";

/// Demonstrate how `if-modified-since` reports that matching objects haven't
/// changed.
///
/// # Steps
/// - Create a bucket.
/// - Put an object in the bucket.
/// - Get the bucket headers.
/// - Get the bucket headers again but only if modified.
/// - Delete the bucket.
#[tokio::main]
async fn main() -> Result<(), Error> {
    tracing_subscriber::fmt::init();

    // Get a new UUID to use when creating a unique bucket name.
    let uuid = uuid::Uuid::new_v4();

    // Load the AWS configuration from the environment.
    let client = Client::new(&aws_config::load_from_env().await);

    // Generate a unique bucket name using the previously generated UUID.
    // Then create a new bucket with that name.
    let bucket_name = format!("if-modified-since-{uuid}");
    client
        .create_bucket()
        .bucket(bucket_name.clone())
        .send()
        .await?;

    // Create a new object in the bucket whose name is `KEY` and whose
    // contents are `BODY`.
    let put_object_output = client
        .put_object()
        .bucket(bucket_name.as_str())
        .key(KEY)
        .body(ByteStream::from_static(BODY.as_bytes()))
        .send()
        .await;

    // If the `PutObject` succeeded, get the eTag string from it. Otherwise,
    // report an error and return an empty string.
    let e_tag_1 = match put_object_output {
        Ok(put_object) => put_object.e_tag.unwrap(),
        Err(err) => {
            error!("{err:?}");
            String::new()
        }
    };

    // Request the object's headers.
    let head_object_output = client
        .head_object()
        .bucket(bucket_name.as_str())
        .key(KEY)
        .send()
        .await;

    // If the `HeadObject` request succeeded, create a tuple containing the
    // values of the headers `last-modified` and `etag`. If the request
    // failed, return the error in a tuple instead.
    let (last_modified, e_tag_2) = match head_object_output {
        Ok(head_object) => (
            Ok(head_object.last_modified().cloned().unwrap()),
            head_object.e_tag.unwrap(),
        ),
        Err(err) => (Err(err), String::new()),
    };

    warn!("last modified: {last_modified:?}");
    assert_eq!(
        e_tag_1, e_tag_2,
        "PutObject and first GetObject had differing eTags"
    );

    println!("First value of last_modified: {last_modified:?}");
    println!("First tag: {}\n", e_tag_1);

    // Send a second `HeadObject` request. This time, the `if_modified_since`
    // option is specified, giving the `last_modified` value returned by the
    // first call to `HeadObject`.
    //
    // Since the object hasn't been changed, and there are no other objects in
    // the bucket, there should be no matching objects.

    let head_object_output = client
        .head_object()
        .bucket(bucket_name.as_str())
        .key(KEY)
        .if_modified_since(last_modified.unwrap())
        .send()
        .await;

    // If the `HeadObject` request succeeded, the result is a typle containing
    // the `last_modified` and `e_tag_1` properties. This is _not_ the expected
    // result.
    //
    // The _expected_ result of the second call to `HeadObject` is an
    // `SdkError::ServiceError` containing the HTTP error response. If that's
    // the case and the HTTP status is 304 (not modified), the output is a
    // tuple containing the values of the HTTP `last-modified` and `etag`
    // headers.
    //
    // If any other HTTP error occurred, the error is returned as an
    // `SdkError::ServiceError`.

    let (last_modified, e_tag_2): (Result<DateTime, SdkError<HeadObjectError>>, String) =
        match head_object_output {
            Ok(head_object) => (
                Ok(head_object.last_modified().cloned().unwrap()),
                head_object.e_tag.unwrap(),
            ),
            Err(err) => match err {
                SdkError::ServiceError(err) => {
                    // Get the raw HTTP response. If its status is 304, the
                    // object has not changed. This is the expected code path.
                    let http = err.raw();
                    match http.status().as_u16() {
                        // If the HTTP status is 304: Not Modified, return a
                        // tuple containing the values of the HTTP
                        // `last-modified` and `etag` headers.
                        304 => (
                            Ok(DateTime::from_str(
                                http.headers().get("last-modified").unwrap(),
                                DateTimeFormat::HttpDate,
                            )
                            .unwrap()),
                            http.headers().get("etag").map(|t| t.into()).unwrap(),
                        ),
                        // Any other HTTP status code is returned as an
                        // `SdkError::ServiceError`.
                        _ => (Err(SdkError::ServiceError(err)), String::new()),
                    }
                }
                // Any other kind of error is returned in a tuple containing the
                // error and an empty string.
                _ => (Err(err), String::new()),
            },
        };

    warn!("last modified: {last_modified:?}");
    assert_eq!(
        e_tag_1, e_tag_2,
        "PutObject and second HeadObject had different eTags"
    );

    println!("Second value of last modified: {last_modified:?}");
    println!("Second tag: {}", e_tag_2);

    // Clean up by deleting the object and the bucket.
    client
        .delete_object()
        .bucket(bucket_name.as_str())
        .key(KEY)
        .send()
        .await?;

    client
        .delete_bucket()
        .bucket(bucket_name.as_str())
        .send()
        .await?;

    Ok(())
}

• API 세부 정보는 Rust용 AWS SDK API 참조의 GetObject를 참조하십시오.

AWS SDK 개발자 가이드 및 코드 예시의 전체 목록은 AWS SDK와 함께 이 서비스 사용 단원을 참조하세요. 이 주제에는 시작하기에 대한 정보와 이전 SDK 버전에 대한 세부 정보도 포함되어 있습니다.