René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add Canonicalized_Extension_Headers for signedURL builder","articleBody":"Cloud Storage SignedURLs allows for custom headers you can set to define metadata:\r\n\r\n* [https://cloud.google.com/storage/docs/access-control/signed-urls#string-components](https://cloud.google.com/storage/docs/access-control/signed-urls#string-components)\r\n\r\nIt doesn't look like you can add this in now during signURL construction:\r\n\r\n* [StorageImpl.java](https://github.com/GoogleCloudPlatform/google-cloud-java/blob/337ca2f234755453e04e2915880520bb6bcbd4c3/google-cloud-storage/src/main/java/com/google/cloud/storage/StorageImpl.java#L494)\r\n\r\nnote BlobInfo has metadata defined in it already so maybe use that:\r\n  * [BlobInfo.java](https://github.com/GoogleCloudPlatform/google-cloud-java/blob/337ca2f234755453e04e2915880520bb6bcbd4c3/google-cloud-storage/src/main/java/com/google/cloud/storage/BlobInfo.java#L255)\r\n\r\nthe following shows how to manually construct the signed URL with canonical headers outside of this library\r\n\r\n\r\n```java\r\nServiceAccountCredentials creds = ServiceAccountCredentials.fromStream(new FileInputStream(\"YOUR_CERT.json\")); \r\n\r\nString BUCKET_NAME = \"your_bucket\"; \r\nString OBJECT_NAME = \"a.txt\"; \r\nString SERVICE_ACCOUNT_EMAIL = \"svc-2-429@your_project.iam.gserviceaccount.com\"; \r\nString verb = \"PUT\"; \r\nlong expiration = System.currentTimeMillis()/1000 + 60; \r\nString Canonicalized_Extension_Headers = \"x-goog-meta-icecreamflavor:vanilla\"; \r\n\r\n\r\nbyte[] sr = creds.sign( (verb + \"\\n\\n\\n\" + expiration + \"\\n\" + Canonicalized_Extension_Headers + \r\n\"\\n\" + \"/\" + BUCKET_NAME + \"/\" + OBJECT_NAME ).getBytes() ); \r\nString url_signature = new String(Base64.encodeBase64( sr )); \r\nString signed_url = \"https://storage.googleapis.com/\" + BUCKET_NAME + \"/\" + OBJECT_NAME + \r\n\"?GoogleAccessId=\" + SERVICE_ACCOUNT_EMAIL + \r\n\"\u0026Expires=\" + expiration + \r\n\"\u0026Signature=\" + URLEncoder.encode(url_signature, \"UTF-8\"); \r\n\r\nSystem.out.println(signed_url); \r\n```\r\n\r\nJust to note, you'll need to post the headers too but thats outside of this FR:\r\n```\r\ncurl -v -H \"x-goog-meta-icecreamflavor:vanilla\" -X PUT \"https://storage.googleapis.com/.....\u0026Signature=Ol1zLbXd0W%2B3q....3D%3D\" --upload-file a.txt \r\n```","author":{"url":"https://github.com/salrashid123","@type":"Person","name":"salrashid123"},"datePublished":"2017-04-26T00:01:41.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/2000/google-cloud-java/issues/2000"}