HeadObject 搭配 AWS SDK或 使用 CLI

下列程式碼範例示範如何使用 HeadObject。

CLI

AWS CLI

下列命令會擷取名為 之儲存貯體中物件的中繼資料my-bucket：

aws s3api head-object --bucket my-bucket --key index.html

輸出：

{
    "AcceptRanges": "bytes",
    "ContentType": "text/html",
    "LastModified": "Thu, 16 Apr 2015 18:19:14 GMT",
    "ContentLength": 77,
    "VersionId": "null",
    "ETag": "\"30a6ec7e1a9ad79c203d05a589c8b400\"",
    "Metadata": {}
}

• 如需API詳細資訊，請參閱 命令參考 HeadObject中的 。 AWS CLI

Java

SDK 適用於 Java 2.x

注意

還有更多 。 GitHub尋找完整範例，並了解如何在 AWS 程式碼範例儲存庫中設定和執行。

判斷物件的內容類型。

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.HeadObjectRequest;
import software.amazon.awssdk.services.s3.model.HeadObjectResponse;
import software.amazon.awssdk.services.s3.model.S3Exception;

/**
 * Before running this Java V2 code example, set up your development
 * environment, including your credentials.
 * <p>
 * For more information, see the following documentation topic:
 * <p>
 * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 */
public class GetObjectContentType {
    public static void main(String[] args) {
        final String usage = """

            Usage:
                <bucketName> <keyName>

            Where:
                bucketName - The Amazon S3 bucket name.\s
                keyName - The key name.\s
            """;

        if (args.length != 2) {
            System.out.println(usage);
            System.exit(1);
        }

        String bucketName = args[0];
        String keyName = args[1];
        Region region = Region.US_EAST_1;
        S3Client s3 = S3Client.builder()
            .region(region)
            .build();

        getContentType(s3, bucketName, keyName);
        s3.close();
    }

    /**
     * Retrieves the content type of an object stored in an Amazon S3 bucket.
     *
     * @param s3 an instance of the {@link S3Client} class, which is used to interact with the Amazon S3 service
     * @param bucketName the name of the S3 bucket where the object is stored
     * @param keyName the key (file name) of the object in the S3 bucket
     */
    public static void getContentType(S3Client s3, String bucketName, String keyName) {
        try {
            HeadObjectRequest objectRequest = HeadObjectRequest.builder()
                .key(keyName)
                .bucket(bucketName)
                .build();

            HeadObjectResponse objectHead = s3.headObject(objectRequest);
            String type = objectHead.contentType();
            System.out.println("The object content type is " + type);

        } catch (S3Exception e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }
    }
}

取得物件的還原狀態。

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.HeadObjectRequest;
import software.amazon.awssdk.services.s3.model.HeadObjectResponse;
import software.amazon.awssdk.services.s3.model.S3Exception;

public class GetObjectRestoreStatus {
    public static void main(String[] args) {
        final String usage = """

            Usage:
                <bucketName> <keyName>\s

            Where:
                bucketName - The Amazon S3 bucket name.\s
                keyName - A key name that represents the object.\s
            """;

        if (args.length != 2) {
            System.out.println(usage);
            System.exit(1);
        }

        String bucketName = args[0];
        String keyName = args[1];
        Region region = Region.US_EAST_1;
        S3Client s3 = S3Client.builder()
            .region(region)
            .build();

        checkStatus(s3, bucketName, keyName);
        s3.close();
    }

    /**
     * Checks the restoration status of an Amazon S3 object.
     *
     * @param s3         an instance of the {@link S3Client} class used to interact with the Amazon S3 service
     * @param bucketName the name of the Amazon S3 bucket where the object is stored
     * @param keyName    the name of the Amazon S3 object to be checked
     * @throws S3Exception if an error occurs while interacting with the Amazon S3 service
     */
    public static void checkStatus(S3Client s3, String bucketName, String keyName) {
        try {
            HeadObjectRequest headObjectRequest = HeadObjectRequest.builder()
                .bucket(bucketName)
                .key(keyName)
                .build();

            HeadObjectResponse response = s3.headObject(headObjectRequest);
            System.out.println("The Amazon S3 object restoration status is " + response.restore());

        } catch (S3Exception e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }
    }
}

• 如需API詳細資訊，請參閱 參考 HeadObject中的 。 AWS SDK for Java 2.x API

Ruby

SDK 適用於 Ruby

注意

還有更多 。 GitHub尋找完整範例，並了解如何在 AWS 程式碼範例儲存庫中設定和執行。

require 'aws-sdk-s3'

# Wraps Amazon S3 object actions.
class ObjectExistsWrapper
  attr_reader :object

  # @param object [Aws::S3::Object] An Amazon S3 object.
  def initialize(object)
    @object = object
  end

  # Checks whether the object exists.
  #
  # @return [Boolean] True if the object exists; otherwise false.
  def exists?
    @object.exists?
  rescue Aws::Errors::ServiceError => e
    puts "Couldn't check existence of object #{@object.bucket.name}:#{@object.key}. Here's why: #{e.message}"
    false
  end
end

# Example usage:
def run_demo
  bucket_name = "amzn-s3-demo-bucket"
  object_key = "my-object.txt"

  wrapper = ObjectExistsWrapper.new(Aws::S3::Object.new(bucket_name, object_key))
  exists = wrapper.exists?

  puts "Object #{object_key} #{exists ? 'does' : 'does not'} exist."
end

run_demo if $PROGRAM_NAME == __FILE__

• 如需API詳細資訊，請參閱 參考 HeadObject中的 。 AWS SDK for Ruby API