Java

S3 Get Object Metadata, such as ETag

See more Amazon S3 (new) Examples

Demonstrates how to get an S3 object's metadata using a HEAD request. Chilkat2 Java

import com.chilkatsoft.chilkat2.AuthAws;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Rest;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        Rest rest = new Rest();

        // Connect to the Amazon AWS REST server in the desired region.
        // In this case we connect to S3 in the "us-west-2" region.
        boolean bTls = true;
        int port = 443;
        boolean bAutoReconnect = true;
        rest.connect("s3-us-west-2.amazonaws.com", port, bTls, bAutoReconnect);

        // Provide AWS credentials.
        AuthAws authAws = new AuthAws();
        authAws.setAccessKey("AWS_ACCESS_KEY");
        authAws.setSecretKey("AWS_SECRET_KEY");
        authAws.setServiceName("s3");

        // This particular bucket is in the Oregon region, as opposed to the US Standard,
        // therefore the Region must be set appropriately.
        // Also note that we connected to "s3-us-west-2.amazonaws.com".
        authAws.setRegion("us-west-2");

        rest.setAuthAws(authAws);

        // Note: The above REST connection and setup of the AWS credentials
        // can be done once.  After connecting, any number of REST calls can be made.
        // The "auto reconnect" property passed to rest.Connect indicates that if
        // the connection is lost, a REST method call will automatically reconnect
        // if needed.
        // --------------------------------------------------------------------------

        // Set the bucket name via the HOST header.
        // In this case, the bucket name is "chilkat.ocean".
        // Note that the Host header should use "bucketName.s3.amazonaws.com", not "bucketName.s3-us-west-2.amazonaws.com"
        rest.setHost("chilkat.ocean.s3.amazonaws.com");

        // Our object is "starfish.jpg".
        // Get the metadata.
        // Since we are sending a HEAD request, we shouldn't use any of the Full* methods.
        // Instead, send the request, then just read the response header.
        try {
            rest.sendReqNoBody("HEAD", "/starfish.jpg");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Now get the response header.
        int statusCode = rest.readResponseHeader();
        if (statusCode < 0) {
            System.out.println(rest.getLastErrorText());
            return;
        }

        // When successful, the S3 Storage service will respond with a 200 response code,
        // with an XML body.
        if (statusCode != 200) {
            // Examine the request/response to see what happened.
            System.out.println("response status code = " + statusCode);
            System.out.println("response status text = " + rest.getResponseStatusText());
            System.out.println("response header: " + rest.getResponseHeader());
            return;
        }

        // The response header contains information about the S3 object.
        // For example:

        //     HTTP/1.1 200 OK
        //     x-amz-id-2: GrV/hrB2EUkBlWc0h3JDdmVIrYDXfPC7CGvo/qSVRmYRPwilAOry8+4r2YWl4xJfa1HRYXrP808=
        //     x-amz-request-id: 4BDC6D6AEA0BDEF3
        //     Date: Mon, 13 May 2019 22:03:13 GMT
        //     Last-Modified: Mon, 10 Nov 2014 16:10:23 GMT
        //     ETag: "2e9c59dbf2662367dc97dfdda85da048"
        //     Accept-Ranges: bytes
        //     Content-Type: image/jpg
        //     Content-Length: 6229
        //     Server: AmazonS3

        // Get the ETag response header value:
        String etag = rest.responseHdrByName("ETag");
        System.out.println("ETag: " + etag);
    }
}