Gets the object stored in Amazon S3 under the specified bucket and key. Returns null if the specified constraints weren't met. To get an object from Amazon S3, the caller must have Permission#Read access to the object. Callers should be very careful when using this method; the returned Amazon S3 object contains a direct stream of data from the HTTP connection. The underlying HTTP connection cannot be closed until the user finishes reading the data and closes the stream. Regarding conditional get constraints, Amazon S3 will ignore any dates occurring in the future.