Choosing the right Development Model

Web Connection supports a number of different ways for creating Web applications from very high level approaches like the Web Control Framework to low level approaches where you can use pure code to output every single byte of content sent back over the HTTP connection yourself. Which approach you use depends on your preferences and your application's needs. Here's an overview of some of the approaches available.

  • Level Code Only Development
  • Model View Controller (MVC) Scripts and Templates
  • REST Services

Low Level Code Only Development

Like any Web development framework, Web Connection has raw HTTP output mechanisms for sending output directly into the HTTP stream. Web Connection uses these features internally to build core abstractions as well as the higher level frameworks discussed below. The same features are also available to you to use in your application code.

You can use raw Response.Write() commands to write out Html from code for example. There are also a number of Html helpers that facilitate generate a few HTML abstractions directly from code. It might be very tempting to build small applications this way. While this works, it generally not a good idea to create Html output purely from code directly in wwProcess methods as it ends up creating a lot of extra code that is mixed with your business logic. It's also much harder to edit HTML in code than say in an external HTML editor as you would with MVC for example.

Low level access is useful for many things - if you have requests that return file or image content as part of your application for example, it's useful to create individual methods that specifically use low level Response.Write() and header access. If you are building a custom framework on top of Web Connection then too it makes good sense to use the low level access methods. But for typical application code, it's usually not a good choice.

Pros

  • Logical First Step
  • Easy to understand and write

Cons

  • Difficult to maintain
  • Have to recompile for each HTML change
  • Can't use sophisticated HTML Editing tools

As a general rule: It's OK to experiment with low level output when you get started, but as you build real applications, it's best to choose another pattern for creating output. Unless you are building a custom framework, or a purely meta data driven output engine type application, code based HTML generation is rarely a good idea.

Hello World Example

Raw HTML output is exactly as you would expect: You write out code using the Response object directly from within a Process method in your wwProcess subclass:

*** wwProcess Method
FUNCTION HelloWord()

lcName = Request.QueryString("name")

TEXT TO lcText NOSHOW TEXTMERGE 
<html>
<body>
   <h1>Hello << lcName >></h1>
   <hr />
   Nice to meet 'ya. Time is: << Time() >>
</body>
</html>

Response.Write(lcHtml)
ENDFUNC

MVC style Scripts and Templates

A very common Web development pattern is known as MVC:

  • Model
    This refers to the data in your applications. This can be in the form of data retrieved from tabels, or view model objects that message data into the required data to be ready for display.

  • View
    A view is responsible for turning passed in Model data (if any) into output - typically an HTML document. This is done via templates or scripts that typically mix HTML with code expressions and bits of control statement code (if, case, for, while, scan etc.) to produce the final text merged output. In Web Connection this is done via Scripts and Templates that let you use FoxPro code within Html templates using ASP like template expansion syntax (<%= expression %>).

  • Controller
    The controller is the entry point for an MVC request. In Web Connection it's a Process method that receives a request. The controller receives input via the Request object, then runs the logic required to create a Model from the Request. Controller code should preferrably defer operations to other objects to perform the heavy application logic responsible for retrieving or updating of data using Business objects or other abstracted data operations. The result that is returned can then be sent to the view for rendering. If necessary the result data can be stored into an explicitly created View Model object that further formats and messages the data so it's ready for display in the View.

MVC is an attractive strategy for Web development as it results in small bits of Controller code, with the display logic moved into an external HTML template that behaves like a standard HTML document with embedded server logic. Because the file is external, you can use standard HTML editors for editing HTML rather than editing HTML in code. Templates and scripts are external to your code project, so you can easily change them without recompiling and redeploying your entire project.

MVC is a commonly used pattern for Web Development so it's familar to developers for other frameworks. If you move to another technology in the future you are likely to find MVC frameworks and might even be able to reuse most of your HTML template content.

more info on Scripts and Templates

Pros

  • Very easy to understand and get started with
  • Efficient and fast executing code
  • Easy to modify templates on the fly
  • Use standard HTML editors

Cons

  • Templates and Scripts have some processing overhead
  • Script Compilation at runtime can be confusing

Hello World Example

HTML Markup:

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>HelloWorld</title>
    <link href="../westwind.css" rel="stylesheet" type="text/css" />
</head>
<body>
    <form id="form1" runat="server" method="POST">

    <h1>HelloWorld</h1>
    
    <div class="containercontent">    
        Enter your name:
        <input type="textbox" id="txtName" name="txtName" value="<%= pcName %>" />
        <input type="submit" id="btnSayHello" name="btnSayHello" value="Say Hello" />
        <hr />
        <%= pcMessage %>
    </div>
    
    </form>
</body>
</html>

The FoxPro Controller code in a Process class method then looks like this:

FUNCTION HelloWorldTemplate
PRIVATE pcName, pcMessage

*** Variables to embed in the Template View
pcName = ""
pcMessage = ""

*** if we're posting back
IF Request.IsFormVar("btnSayHello")
   pcName = Request.Form("txtName")
   pcMessage = "Hello World " + pcName + ". Time is: " + TIME()
ENDIF

* **Call the template from Web path (HelloWorldTemplate.wwd)
* **Alternately you can explicitly point at a path
Response.ExpandScript( )

*** Some Alternatives
* Response.ExpandScript(Response.GetPhysicalPath())
* Response.ExpandScript("~/SomeOtherPage.wwd")
* Response.ExpandTemplate()

ENDFUNC

REST API

You can also build API Services quite easily with Web Connection. APIs are non-visual interfaces that return raw data, rather than HTML. You pass data/parameters to a service, the service does some work based on the input and then returns a data result - most commonly in JSON format.

The approach is very similar to the way you build an MVC application minus the HTML template merging to render your model. Rather than rendering a model to HTML, an API simply returns a result value which is turned into JSON or XML.

As with MVC, REST API services work with a custom Process class (which is the top level 'handler') that handle the routing of requests to the appropriate methods as well as de-serializing incoming JSON data to FoxPro value/objects and serializing the return value into JSON.

Each method can take a single POST or PUT JSON parameter as input, or you can use Form and Query variables just as you can in standard wwProcess handlers.

More info on REST Services

What does a REST API Look like?

An API endpoint is just a method inside of a wwProcess class with a single input parameter and a return value. The input can map an optional single JSON value, object or collection into a FoxPro object. Your code can then use that object to create new output in the form of a result value, object, collection or cursor.

Here's a simple example:

*********************************************************************
FUNCTION GetData(lvParm)
************************

*** Any posted JSON string is automatically deserialized
*** into lvParm FoxPro object or value 

*** In this example an object with multiple query values
*** was passed
lcSearchName = lvParm.searchName
lcSearchDate = lvParm.searchDate


*** Run your business logic...
select * from customers ;
    where lastName = lcSearchName AND ; 
          entered > lcSearchDate ; 
    into cursor TCustomers
    

*** Simply create objects, collections, values and return them
*** they are automatically serialized to JSON

*** Create an object on the fly here to return 'multiple' values
*** But you can return any object, collection, cursor or value
loObject = CREATEOBJECT("EMPTY")
ADDPROPERTY(loObject,"searchFor",lcSearchName)
ADDPROPERTY(loObject,"serachDate", lcSearchDate)

*** Attach the cursor as a JSON array
ADDPROPERTY(loObject,"customers","cursor:TCustomers")


*** Properties by default serialize to *all lower case*
*** This allows overriding property case for specific properties
Serializer.PropertyNameOverrides = "searchFor,searchDate"

*** Return value of this API - serialized to JSON
RETURN loObject

A client could POST to this API with the following JSON:

{
    searchFor: "Strahl",
    searchDate: "2018-09-27T18:00:00Z"
}

The method then produces the following output:

{
    searchFor: "Strahl",
    searchDate: "2018-09-27T18:00:00Z",
    customers: [  
        lastname: "Strahl",
        firstname: "Rick",
        entered: "2018-09-29T18:00:00Z",
        ...
    ]
}

In short it's very simple to create APIs using this interface.

Pros

  • Very easy to understand and get started with
  • Efficient and fast executing code
  • Great for any sort of Data access from HTTP clients

Cons

  • FoxPro JSON conversion issues - casing requires special fix up
  • Huge data sets can be slow

© West Wind Technologies, 1996-2022 • Updated: 01/17/22
Comment or report problem with topic