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Sunday, May 5, 2013Print Subscribe

Both Azure Storage and Amazon S3 require a couple of security parameters and repository name in order to upload or download a file. The data controller configurations of both adapters require explicit definition of these parameters.

Let’s consider the configuration of an Azure Blob Adapter.

Field: Picture
Storage-System: Azure
Account: northwindproductpictures
Container: pics
Key: e2Wl668b6fEGauS6cOTAHaj7Ut6QfwKdbGY4Vd8yngz40y2f54M5EfZtSNNHYoXW7i7+kZAfFJrg==
Path-Template: Products/{ProductID}-{PictureFileName}

The application framework allows providing default values for Account, Container, and Key.

Start the app generator. Select your project and click Develop. The project will be opened in Visual Studio. In the Solution Explorer, right-click on ~\App_Code\Data, and press Add | Add New Item…

Select Class from the list, specify a name, and press OK to add the new file.

Replace the code base with the following. Use your own key instead of the highlighted text.

C#:

using System;

namespace MyCompany.Data
{
    public partial class AzureBlobAdapter
    {
        public override string Key
        {
            get
            {
                return "ENTER KEY HERE";
            }
        }
    }
}

Visual Basic:

Imports Microsoft.VisualBasic

Namespace MyCompany.Data
    Partial Public Class AzureBlobAdapter
        Public Overrides Property Key As String
            Get
                Return "ENTER KEY HERE"
            End Get
            Set(value As String)
                MyBase.Key = value
            End Set
        End Property
    End Class
End Namespace

Save the file, and activate the Project Designer. In the Project Explorer, switch to the Controllers tab and double-click on Products. Change the Blob Adapter Configuration as shown below.

Field: Picture
Storage-System: Azure
Account: northwindproductpictures
Container: pics
Path-Template: Products/{ProductID}-{PictureFileName}

The application framework will now use the key explicitly returned by the AzureBlobAdapter.Key property.

The Account and Container properties may also be overridden in a similar fashion to further simplify the adapter configuration. Multiple virtual binary fields may share the same Account, Container, and Key. The implementation of the properties may optionally read values from the database depending on the user identity, role, or other conditions.

The Amazon S3 Adapter allows overriding properties AccessKeyID, SecretAccessKey, and Bucket.

Labels: Application Builder, BLOB, Web Application Generator

Thursday, May 2, 2013Print Subscribe

Code On Time Tools for Excel, Upload/Download Adapters

Code On Time release 7.0.8.0 introduces support for Tools for Excel. This new alternative development environment is an add-in for Microsoft Excel 2010 - 2013. It provides a bird-eye view of project configuration element properties with the ability to make rapid and massive changes. Download Tools for Excel at http://codeontime.com/releases/tools-for-excel and use them alongside the Project Designer built in the application generator.

Application framework in the core of web apps created with Code On Time now supports virtual binary fields that can be stored in the File System, Windows Azure Storage, or Amazon S3. Store your binary content in the external storage systems without writing a single line of code with the help of upload/download adapters. Adapters are implemented without dependencies on the external libraries. All communications with external storage systems are performed through the corresponding REST APIs.

The following features and enhancements were introduced in the new release:

Code On Time Tools for Excel
File Upload/Download Adapters
jQuery 1.9.1 and jQuery UI 1.10.2 are now integrated in the client library.
Metadata Builder has been enhanced to support cross-synonym references for Oracle databases.
Auto-refresh of data views will automatically sync a view to show the last selected data row. Auto-refresh will not be performed on form views.
Implementation of ActionResult.ShowModal will correctly display modal views of the current controller.

The next release with the new preview of the second generation data sheet view will go out soon. We expect to introduce Mobile Client Library and upload/download adapter for Google Drive in May of 2013.

Labels: Application Builder, BLOB, COT Tools for Excel, Designer, Release Notes, Web Application Generator

Monday, April 29, 2013Print Subscribe

Overview of Upload/Download Adapters

Large files are frequently stored in databases as BLOB fields (binary large objects). Code On Time offers out-of-the-box support for upload and download of content directly to BLOB table columns. However, common practice is to store the binary content outside of the database. There are numerous advantages to this approach:

Reduced database size
Simplified backup
Low cost of storing large amounts of data
Opportunity to create a content delivery network (CDN)

File System

The most common method to store external files is in the file system. The files can be saved on the same hard drive of the host machine, or on an external Network-Attached Storage (NAS) device. While these devices are simple to configure, they still will require maintenance to ensure redundancy and performance.

Azure Storage

Microsoft Azure Storage cloud platform is a high-redundancy and availability solution that stores all data in data centers managed by Microsoft. It offers geo redundant storage, affinity groups, and logging. Each storage account can open multiple “containers” that are accessed via HTTP requests using unique container keys. Containers may be declared as “public” if necessary.

Amazon S3

Amazon Simple Storage Service (Amazon S3) is another popular cloud solution that offers features similar to Microsoft Azure Storage. It offers data redundancy and high availability, enabling rapid scaling of application infrastructure. Each account can create multiple buckets to store data, which are accessed via HTTP requests using one or more “Secret Access Keys”.

Configuring an Upload/Download Adapter

Declare virtual BLOB fields by entering a few parameters in the BLOB Adapter Configuration of a data controller. The web application framework will perform REST requests to a specified storage system, making it possible to use any combination of adapters in a single application without creating dependencies on third-party libraries.

A physical table column storing the file name is required for each virtual BLOB field definition. It allows the application framework to determine existence of binary content.

Optional utility table columns Length and Content Type may be specified. The matching data controller fields will enable the application framework to communicate the file type and size to the client browser.

The table below shows configuration parameters that may be used to set up an adapter.

Parameter	Description	Storage System
Access-Key-ID	The Access Key ID of the specified Secret Access Key required to form secure requests to Amazon S3.	S3
Account	Name of the Azure Storage Account.	Azure
Bucket	The bucket that stores the binary content.	S3
Container	The container that stores the binary content.	Azure
Content-Type-Field	The name of the data controller field that stores the file content type (data type String).	Optional
Field	The name of the virtual BLOB field.	Required
File-Name-Field	The name of the field that stores the file name (data type String).	Required
Key	The key used to authenticate Azure Storage requests.	Azure
Length-Field	The name of the data controller field that stores the file length (data type Int).	Optional
Path-Template	The path to the binary content in the storage system. May include references to data controller field names and special names.	Required
Storage-System	The type of storage system that holds the binary content. Supported values are “File”, “Azure”, and “S3”.	Required
Secret-Access-Key	The Secret Access Key used in conjunction with Access Key ID to form secure requests to Amazon S3.	S3

Configuring Path Template

The path template can reference data controller field names in curly brackets ({}). The following example references the data controller fields ProductID and PictureFileName. This path template will work with Azure and S3 storage systems.

Path-Template: Products/{ProductID}-{PictureFileName}

The file system path template must resolve as a physical path in the file system.

Path-Template: C:\Northwind\Customers\{CustomerID}-{PhotoFileName}

You can also specify a path relative to the application root when using file system storage.

Path-Template: ~\App_Data\Customers\{CustomerID}-{PhotoFileName}

Special names $Extension and $FileNameWithoutExtension can also be used in the path template with any storage system.

Path-Template: Products/{$FileNameWithoutExtension}-{ProductID}.{$Extension}

Most hosted storage systems (Azure, S3, Google Drive) are only supporting a limited set of characters in the path. The application framework will automatically replace non-alphanumeric characters with dash (-) when evaluating path templates.

Labels: Application Builder, Azure, BLOB, Tutorials, Web Application Generator