Tutorial: Creating Web Forms in COBOL

Overview

This tutorial shows how to create a Web page and how to make this interact with an existing COBOL program. The page is generated in managed COBOL. The page calls an intermediary program to map .NET data types onto COBOL data types. The intermediary program then calls the existing COBOL program to perform the business logic.

The Web Site has three programs:

Web page. The Microsoft form designer enables you to create a Web page (also known as a Web form) in any .NET language, such as C# and COBOL. This tutorial shows how to generate these forms in .NET COBOL.
Existing COBOL program, the Book program. This program simulates a pre-existing COBOL program, which contains the business logic and which remains unchanged. This program is supplied and this tutorial adds it to the Web Site so that it is recompiled as managed code and exposed as a class that can be called by .NET managed code without needing any changes to the source.
Intermediary COBOL class, the BookWrapper program. This program acts as an interface between the client form and the pre-existing COBOL program. This intermediary class interfaces with the .NET client form using objects, and it interfaces with the existing COBOL using the standard COBOL PIC X data types. This intermediary class is supplied and this tutorial adds it to the Web Site.

Prerequisites

As a prerequisite step for this tutorial, you need to build the BookWrapper and LegacyBook projects that are part of the WinBook sample as follows:

Start the Visual COBOL Samples Browser. If you need instructions, see To start the Samples Browser.
Click Windows Forms in the left pane and then Win Book.
Click Open sample in Visual Studio.
In Solution Explorer, right-click WinBook solution and choose Build Solution.

The build creates two binaries, BookWrapper.dll and LegacyBook.dll, in the bin subfolder of the WinBook solution.

Create a Web Site

The first task is to create a Web Site, which you do as follows:

Start Visual Studio.
Create a new Web Site by clicking File > New > Web Site.
Expand Installed > Templates and click COBOL.
Ensure .NET Framework 4.5 is selected in the dropdown list above the installed templates pane.
Select ASP.NET Web Site.
In the Web location field, select File System and browse to a directory where you want to put this tutorial, and specify the directory WebBook.
Click OK.

This creates the WebBook Web Site, which is then displayed in the Solution Explorer. The Web Site contains:

App_Data, which is an empty folder for holding application data
Default.aspx, which is the trigger program that displays the main form
Default.aspx.cbl, which contains your code for the form
Web.config, which is the application configuration file

A Web Site appears in the solution explorer in a similar way to a project, but a Web Site is not a project. It is a directory, which enables you to publish the Web Site simply. For full details see the Visual Studio Help, such as the topic .NET Development\Web Applications. This tutorial shows some of the other differences, which include:

A Web Site does not have extensive project properties, but has Web configuration settings in the Web.config file. You use the Web.config file to specify the location of copybooks, copypath, which is added to the directives file or to the COBCPY environment variable.
To include dependent code in your Web Site, you add a reference to the code in the usual way, but the code appears in a Bin folder in your Web Site, rather than as a reference in your solution.
You can add Web pages of any language to the Web Site, because it is not a project and is therefore language independent.

Start Painting the Form

In this section, you paint the form. You can also examine the code generated. For basic help on painting a form, see the tutorial Tutorial: Developing .NET COBOL Application.

Display the empty form by right-clicking Default.aspx in the Solution Explorer and clicking View Designer.
Paint four labels, three text boxes and one button on the form.
To lay out the Web form, use spaces and new lines, in the same way as you do in a text editor or in HTML.

Edit the properties of the controls, being careful to not double-click any of the controls. Double-clicking creates an event for the control, which we don't want to do till the next step. Edit the properties to the following values:

Control	ID Property	Text Property
Label	label1	Stock Number
TextBox	textBoxStockNo (the case is significant)	(blank)
Label	label2	Title
TextBox	textBoxTitle (the case is significant)	(blank)
Label	label3	Price
Label	label4 (the case is significant)	(blank)
TextBox	textBoxPrice (the case is significant)	(blank)
Button	button1 (the case is significant)	Search

To display the properties, click the label and then view the Properties pane. You can then scroll to the relevant property and edit it.

Create a click event for the Search button. Do this by double-clicking the button, which creates an event called button1_Click, and then displays the code that is generated for the form.
Notice that the code for the button1_Click method doesn't do anything yet; the procedure division is empty. You can scroll through and review the rest of the generated code.
You can build the form, by clicking Default.aspx in Solution Explorer and choosing Build > Build Page. You should have no errors.

Handle the Click Events

Now you need to add the code for the button click, which needs to call the legacy COBOL program and to populate the form with the information returned.

In code view, find the button1_Click method. Update the code so that it reads as follows:

       method-id  button1_Click protected.
       local-storage section.
       01 input-string string.
       01 my-exception type System.Exception.
       procedure division using by value lnkSender as object lnkEvent as type System.EventArgs.
           set input-string to textBoxStockNo::Text
           try
               set my-book to type BookWrapper.Book::Read(input-string)
               invoke self::PopulateForm(my-book)
           catch my-exception
               invoke self::DisplayException(my-exception)
           end-try
       end method.

Notice the red squigglies underlining some words. These indicate a syntax error from automatic parsing happening in the background. Hover over an underlined word and read the popup that gives information on the error. Notice that the status bar tells you the number of background parsing errors.

Notice that the above code invokes the PopulateForm and the DisplayException method. Add the following methods to your code, after the button1_Click method and before the end object statement.

       method-id  PopulateForm final private.
       procedure division using my-book as type BookWrapper.Book.
           if my-book <> null
               set textBoxStockNo::Text      to my-book::StockNumber
               set textBoxTitle::Text        to my-book::Title
               set textBoxPrice::Text        to type System.Convert::ToString(my-book::RetailPrice)
           else
               set textBoxStockNo::Text      to "****"
               set textBoxTitle::Text        to "*************************************"
               set textBoxPrice::Text        to "****"
           end-if
       end method.

       method-id DisplayException private.
       procedure division using by value lnkException as type System.Exception.
           set label4::Text to lnkException::Message
           set my-book to null
           invoke self::PopulateForm(my-book)
       end method.

Add the Legacy Code and the Wrapper Code

You now need to add the existing COBOL code that contains the business logic, so that the form can use it. This code is supplied in a LegacyBook project containing book.cbl.

In addition, you need some wrapper code to convert the data from .NET types to COBOL types. The Web page uses .NET data types; these are System.String objects in our case. The book program uses COBOL types such as PIC X and PIC 99V99. The supplied program BookWrapper.cbl does this conversion, and you need to add this to the solution.

Create a bin directory for the WebBook Web Site. To do this, right-click the Web Site in the Solution Explorer and click Add > Add ASP.NET Folder > Bin.
Add the prebuilt files for the supplied LegacyBook and BookWrapper programs. To do this, right click Bin in the Solution Explorer, click Add > Add Existing Item and browse to the bin\Debug subfolder in the Forms\WinBook\WinFormBook\bin\Debug folder within the samples folder. Select the .dll files, and also the .pdb files in case you want to debug the application and click Add. The programs are now part of the Web Site.

Provide Access to the Legacy Code

You now need to add some code to the form to call the wrapper code and to clear the last of the red squigglies to do with my-book.

Declare the data item my-book in object working storage, as follows:
```
       01 my-book   type BookWrapper.Book.
```
You should now have no parsing errors, now that BookWrapper is declared.

In the Web.config file, add the following configuration sections after the opening tag line that starts with <configuration>:

<!--The following code declares a section group for application configuration -->
  <configSections>
  <sectionGroup name="MicroFocus.COBOL.Application">
    <section name="Switches" type="System.Configuration.NameValueSectionHandler" />
    <section name="Environment" type="System.Configuration.NameValueSectionHandler" />
  </sectionGroup>
  <!--The following code declares a section group for run-time configuration -->
  <sectionGroup name="MicroFocus.COBOL.Runtime">
    <section name="Tunables" type="System.Configuration.NameValueSectionHandler" />
    <section name="Switches" type="System.Configuration.NameValueSectionHandler" />
  </sectionGroup>
</configSections>

Set up an environment variable to point to the bookfile.* data files, which are supplied in WinBook. To do this:
In the Web.config file, add the following text immediately after the </configSections> line:
```
<appSettings />
<MicroFocus.COBOL.Application>
      <Switches/>
      <Environment>
         <add key="dd_bookfile" value="MyPath\bookfile.dat"/>
      </Environment>
   </MicroFocus.COBOL.Application>
```
Where MyPath is the full path to the data file bookfile.dat, which is in the \Forms\WinBook\WinFormBook\bin\Debug subfolder in the samples.

Run the Application

You can now run the application.

Build the Web Site.
Click Debug > Start Without Debugging.
Experiment entering information and using the Search button.
You can search for data for stock numbers 1111 and 2222.

Examine the Sample Code

The following sections provide a little bit more details about what the sample code does.

Legacy Book Program

The book.cbl program is a long-standing demonstration program that has been shipped with Micro Focus products for several years. It is written in procedural COBOL. The program reads and writes to an indexed file containing book records.

In this solution, the Book program is recompiled to managed code without any changes. Recompiling the program exposes it as a class and exposes its main entry point as a static method.

The program's Linkage section defines data as standard COBOL types, such as PIC X, which non-COBOL client programs do not handle. These types need to be mapped to .NET compatible types before communication with the client program. This mapping is done by the intermediary program BookWrapper.cbl.

Client Web Form

The client Web form Default.aspx.cbl is generated as COBOL. The user enters data into the form and receives the return data there. The client form does the following:

Extracts the input data from text boxes on the form as System.Strings.
Calls BookWrapper passing it the string objects.
Populates the text boxes on the form with the System.Strings.

Book Wrapper Program

The BookWrapper.cbl program acts as an intermediary between the pre-existing COBOL program book.cbl and the Web form. This enables you to leave the pre-existing COBOL unchanged.

The important point here is that you need to use compatible types when mixing languages. The Web form stores the data as .NET types and yet the Book program expects data as COBOL types.

The purpose of the BookWrapper program is to map your COBOL PICTUREs to .NET System.Strings. The program receives data from the Web form as System.Strings, and maps them onto standard COBOL data types before passing them to the pre-existing book program.

The working storage declares the data items in a book record by using a copybook, as follows:

working-storage section.
        copy "book-rec-dotnet.cpy" replacing == (prefix) == by == book ==.
    ...

The copybook book-rec-dotnet.cpy declares the book-details record. It declares book-title and book-stockno as COBOL pictures and also as properties so that Getter/Setter methods can be used to access them. The copybook contains:

    01 (prefix)-details.
        03 (prefix)-text-details.
            05 (prefix)-title  pic x(50) property as "Title".
        ...
        03 (prefix)-stockno pic x(4) property as "StockNumber".

The following property method gets a pointer to the book-details record:

       property-id BookDetails pointer.
       getter. 
           set property-value to address of book-details
       end property.

The Read method is implemented as follows:

       method-id Read static. 
       local-storage section.
       01 file-status pic xx.
       procedure division using by value stockno-in as string
                          returning      myBook     as type BookWrapper.Book. 

           set myBook to new BookWrapper.Book()
           set myBook::StockNumber to stockno-in

           call "BookLegacy" using by value readRecord
                                   by value myBook::BookDetails
                                   by reference file-status       
            
           invoke self:RaiseExceptionIfError(file-status)
           goback.
       end method.

Where:

```
procedure division using ...
```
shows a .NET System.String, stockno-in, being passed in from client form. It also shows an instance of the Book class being returned. BookWrapper.cbl defines a new .NET type, Book, which can be used by programs written in any .NET language.
```
set myBook to new BookWrapper.Book() 
```
creates a new instance of the BookWrapper class.
```
set mybook::StockNumber
```
takes the data from the .NET System.String (stockno-in) and stores it as the StockNumber property of myBook. This property is declared in the copybook as a picture string, and so the data is stored as a standard COBOL data type in book-stockno. The COBOL Compiler implicitly converts the data from the .NET string into a COBOL usage display item (pic x).
```
call BookLegacy using ...
```
calls the legacy program, book.cbl. It passes it the “BookDetails” property of myBook. If you look at the code in BookWrapper.cbl, you can see that what BookDetails does is pass a pointer to the BookRecord structure defined in book-rec-net.cpy. This structure matches the structure in the old book-rec.cpy, so what the legacy Book program sees is a book record being passed in by reference – which is what it expects. Book reads the stock number from this record, reads a record from the indexed file, and then puts the data in the other fields of the record.
```
invoke self::RaiseExceptionIfError(file-status)
```
checks the file status returned from reading the file, and raises a .NET exception if there was an error. Exceptions are the standard .NET mechanism for signaling error conditions.