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Monday, April 29, 2013PrintSubscribe
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.

Wednesday, April 24, 2013PrintSubscribe
Azure Upload/Download Adapter

Microsoft Azure Storage is a low-cost option that allows storing binary content in the cloud. Let’s implement storing of product pictures in the Northwind sample database. We will capture name, size, and content type of the picture file in the Products table. The actual pictures will be saved in Microsoft Azure Storage.

Setting Up Azure Storage

Navigate to http://azure.com and click on the Portal link in the top right corner to log in to your Azure account. If you do not have an account, a free three month trial is offered.

When the Management tool loads, click on the New button in the bottom left corner. Select Data Services | Storage | Quick Create option. Assign a URL for your new storage and press Create Storage Account.

Creating a new storage account in Windows Azure.

When complete, click on the new storage account name in the list to view details. On the action bar displayed at the bottom, press Manage Access Keys. Copy one of the keys into the clipboard.

Viewing Access Keys for Azure Storage account.

At the top of the form, click on Containers tab. Press Add Container at the bottom of the screen.

Adding a container to a storage account.

Assign a name to the container. If you do not expect the product pictures to be accessible to anonymous users, then leave Access property as “Private”. Click on the Check icon to save.

Creating a new container.

Adding Utility Fields to the Database

Start SQL Server Management Studio. In the Object Explorer, right-click on Databases / Northwind / Tables / dbo.Products, and press Design.

Designing the dbo.Products table in Northwind database.

Add the following columns:

Column Name Data Type Allow Nulls
PictureFileName nvarchar(250) yes
PictureLength int yes
PictureContentType nvarchar(50) yes

Save the changes. Switch to the generator and click on the project name. Select Refresh, check the box next to Products controller, and proceed to refresh the web app.

Refreshing the Products controller.

Configuring BLOB Field

Start the Project Designer. In the Project Explorer, switch to the Controllers tab. Right-click on Products / Fields node, and press New Field.

Adding a new field to Products controller.

Assign the following properties:

Property Value
Name Picture
Type Byte[]
Allow Null Values yes
Value is retrieved on demand yes
Source Fields ProductID
On Demand Handler PictureBlobHandler
On Demand Style Thumbnail
Label Picture

Save the field. Drag the new field node and drop it onto Products / Views / editForm1 to instantiate the field as a data field in the editForm1 view.

Instantiating the Picture field in view 'editForm1'.     'Picture' data field created in 'editForm1' view.

Drag the field onto view grid1 to display the picture in the list of products.

Next, double-click on the Products controller node. Enter the following in BLOB Adapter Configuration.

BLOB Adapter Configuration

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

Note that the values above are not functional. Replace the highlighted parts with your own settings.

Make sure to save the controller.

Viewing the Results

On the toolbar, press Browse. Navigate to the Products page, and edit any record. Note that there is a Picture field which accepts files. Click on the link to upload a file and select a picture from your hard drive. A bar at the top of the page will announce completion of upload and the thumbnail of the picture will be displayed. The utility fields will be updated with the picture file name, length, and content type. If you do not want users to change any utility field values, configure the data fields as Static.

Succesful upload of product picture to Azure.

The thumbnail will display the file extension if the file is not an image.

Extension displayed in thumbnail when file is not an image.

The uploaded files are visible in Azure Management screen.

Files are visible in Azure Management tool.

To upload files larger than 4 MB, you will need to increase the application upload size limit.

Friday, March 30, 2012PrintSubscribe
What is Windows Azure Platform?

Azure Factory allows rapid development of web applications for Microsoft Windows Azure cloud. In minutes you can create cross-browser web applications that look similar to the one in the picture.

Sample Azure Factory application created with Code On Time

Curious what Windows Azure is? Read on or take a look at the Azure Factory tutorial explaining how to create an Azure Factory project and deploy it to the cloud with Code On Time web application generator.

What is Windows Azure Platform?

Windows Azure Platform is a cloud hosting service run by Microsoft that enables you to store data, as well as build and connect apps. Everything is stored in a Microsoft data center - the only thing you have to manage is your application. The applications are hosted on cloud operating systems called Windows Azure. This operating system serves as a runtime for your application. While it can't be accessed directly, it can be interacted with using the Azure Portal. You can create, edit, and delete hosted services, and storage accounts. Rich SQL Azure reporting capabilities are also present.

What is the Windows Azure Platform?

Typical "On-Premise" Application Setup

The usual application setup in your own on-premise data center will include the following items:

  • Firewall
  • Load balancer
  • Application server
  • Database server
  • Other services (access control, security)

This setup will take an exhaustive amount of time and money to implement, and that's just the hardware side. You will also need to install the operating systems and configure them to work together. And how long will this system run until you have to start updating, patching, and fixing everything? When traffic increases, you'll also have to scale this system. Windows Azure offers a better solution.

Typical 'On-Premise' Application Setup

Using Windows Azure

Switch your application to Windows Azure - all the hardware is stored in a Microsoft data center, and there is no need to manage the operating system. All you have to do is deploy your application to the cloud, and everything will take care of itself. This allows you to focus on adding business value and key features to your applications.

With Azure Factory, your job becomes even easier. Point to your database and press Generate. In a few minutes, you will have a full featured web application that is sure to impress peers and customers. Then, press Publish, and you will have everything you need to deploy to Windows Azure.

Using Windows Azure

SQL Azure

Windows Azure allows you to store and run your application in the cloud. SQL Azure will store the the data for your application. It is a relational database using SQL technology, that runs in the Azure cloud. Use the online Database Manager provided by Microsoft, or connect to the database with SQL Server Management Studio 2008 R2. SQL Azure also supports T-SQL.

The database is highly scalable - availability will increase with demand, and price will be dictated by usage. All data is distributed across many nodes, with at least three copies, to insure fault tolerance. If one copy goes down, another copy is automatically activated to insure a seamless experience.

SQL Azure

Continue to Azure Factory