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Context information – PB Docs 115 – PowerBuilder Library

Context information – PB Docs 115

  2. Powerbuilder Documentation
  3. Powerbuilder Documentation Older
  4. Powerbuilder Documentation 11.5
  5. Context information – PB Docs 115

Context information

The PowerBuilder context feature allows applications to access
certain host (non-PowerBuilder) services. This is a PowerBuilder
implementation of functionality similar to the COM QueryInterface.
PowerBuilder provides access to the following host services:

PowerBuilder creates service objects appropriate for the current
execution context (native PowerBuilder or transaction server). This
allows your application to take full advantage of the execution
environment.

The context feature uses seven PowerBuilder service objects: ContextInformation,
ContextKeyword, CORBACurrent, ErrorLogging, Inet, SSLServiceProvider,
and TransactionServer; it also uses the InternetResult object. (The
context feature is sometimes called the Context object, but it is not a
PowerBuilder system object.)

For more information about these objects,
see Objects and Controls
or the PowerBuilder
Browser.

Enabling a service

Before you use a service, you instantiate it by calling the GetContextService function.
When you call this function, PowerBuilder returns a reference to
the instantiated service. Use this reference in dot notation when
calling the service’s functions.

proc.gif To enable a service:

  1. Establish an instance variable of the appropriate
    type:

  2. Instantiate the instance variable by calling the GetContextService function:

Using a CREATE statement

You can instantiate a service object with a PowerScript CREATE statement. However,
this always creates an object for the default context (native PowerBuilder
execution environment), regardless of where the application is running.

Context information service

You use the context information service to obtain information
about an application’s execution context. The service provides
current version information, as well as whether the application
is running in the PowerBuilder execution environment.

Accessing context information

Using the context information service, you can access the
information in Table 21-4.

Table 21-4: Context information
Item Use this function Comment
Full context name GetName Value returned depends on the context:

  • Default: PowerBuilder Runtime
Abbreviated context name GetShortName Value returned depends on the context:

  • Default: PBRUN
Company name GetCompanyName Returns Sybase, Inc.
Version GetVersionName Returns the full version number (for example,
11.5.0.1)
Major version GetMajorVersion Returns the major version number (for example,
11.5)
Minor version GetMinorVersion Returns the minor version number (for example,
0)
Fix version GetFixesVersion Returns the fix version number (for example,
1)

note.gif Using the ClassName function for context information You can also use the ClassName function
to determine the context of the object.

You can use this information to verify that the context supports
the current version. For example, if your application requires features
or fixes from Version 11.5.0.1, you can use the context information
service to check the version in the current execution context.

proc.gif To access context information:

  1. Declare an instance or global variable
    of type ContextInformation:

  2. Create the context information service by calling
    the GetContextService function:

  3. Call context information service functions as
    necessary.

    This example calls the GetShortName function
    to determine the current context and the GetVersionName function
    to determine the current version:

Context keyword service

Use the context keyword service to access environment information
for the current context. In the default environment, this service
returns host workstation environment variables. When running within EAServer, you can use the keyword
service to get a specific component property value (on all EAServer platforms except AIX,
you must use Keyword as the string parameter in the GetContextService function).

For information about using the context keyword service in EAServer, see “Accessing component properties”.

Accessing environment variables

When running in the PowerBuilder execution environment (the
default context), you use this service to return environment variables.

proc.gif To access environment variables:

  1. Declare an instance or global variable
    of type ContextKeyword. Also declare an unbounded array of type
    String to contain returned values:

  2. Create the context information service by calling
    the GetContextService function:

  3. Call the GetContextKeywords function
    to access the environment variable you want. This example calls
    the GetContextKeywords function to determine
    the current application Path:

  4. Extract values from the returned array as necessary.
    When accessing environment variables, the array should always have
    a single element:

CORBACurrent service

Client applications and EAServer components
marked as OTS style can create, control, and obtain information
about EAServer transactions using
functions of the CORBACurrent context service object. The CORBACurrent
object provides most of the methods defined for the CORBA Current
interface.

For more information, see “Client- and component-demarcated
transactions”.

Error logging service

To record errors generated by PowerBuilder objects running
in a transaction server to a log file, create an instance of the
ErrorLogging service object and invoke its log method. For example:

The errors are recorded in the EAServer log
if the component is running in EAServer,
and in the Windows system application log if the component is running
in COM+.

Internet service

Use the Internet service to:

  • Display
    a Web page in the default browser (HyperLinkToURL function, which
    starts the default browser with the specified URL)
  • Access the HTML for a specified page (GetURL function,
    which performs an HTTP Get)
  • Send data to a CGI, ISAPI, or NSAPI program (PostURL function,
    which performs an HTTP Post)

Hyperlinking to a URL

You call the Internet service’s HyperLinkToURL function
to start the default browser with a specified URL.

proc.gif To hyperlink to a URL:

  1. Declare an instance or global variable
    of type Inet:

  2. Create the Internet service by calling the GetContextService function:

  3. Call the HyperLinkToURL function,
    passing the URL of the page to display when the browser starts:

Getting a URL

You call the Internet service’s GetURL function
to perform an HTTP Get, returning raw HTML for
a specified URL. This function returns the raw HTML using the InternetResult
object.

proc.gif To perform an HTTP Get:

  1. Declare an instance or global variable
    of type Inet. Also declare an instance or global variable using
    the descendent InternetResult object as the datatype (n_ir_msgbox in
    this example):

  2. Create the Internet service by calling the GetContextService function:

  3. Create an instance of the descendent InternetResult
    object:

  4. Call the GetURL function, passing
    the URL of the page to be returned and a reference to the instance
    of the descendent InternetResult object:

    When the GetURL function completes, it
    calls the InternetData function defined in the
    descendent InternetResult object, passing the HTML for the specified
    URL.

Posting to a URL

You call the Internet service’s PostURL function
to perform an HTTP Post, sending data to a CGI,
ISAPI, or NSAPI program. This function returns the raw HTML using
the InternetResult object.

proc.gif To perform an HTTP Post:

  1. Declare an instance or global variable
    of type Inet. Also declare an instance or global variable using
    the descendent InternetResult object as the datatype (n_ir_msgbox in
    this example):

  2. Create the Internet service by calling the GetContextService function:

  3. Create an instance of the descendent InternetResult
    object:

  4. Establish the arguments to the PostURL function:

  5. Call the PostURL function,
    passing the URL of the routine to be executed, the arguments, the
    header, an optional server port specification, and a reference to
    the instance of the descendent InternetResult object:

    When the PostURL function completes, it
    calls the InternetData function defined in the
    descendent InternetResult object, passing the HTML returned by the
    specified routine.

Using the InternetResult object

The GetURL and PostURL functions
both receive data in an InternetResult object. This object acts
as a buffer, receiving and caching the asynchronous data as it is
returned by means of the Internet. When all data is received, the InternetResult
object calls its InternetData function, which
you override to process the data as appropriate.

note.gif Implement in descendants of InternetResult You implement this feature by creating standard class user
objects of type InternetResult. In each of these descendent user
objects, define an InternetData function to process
the passed HTML as appropriate.

proc.gif To implement a descendent InternetResult object:

  1. Create a standard class user object of
    type InternetResult.

  2. Declare a new user object function as follows:

    • Name InternetData
    • Access Public
    • Returns Integer
    • Argument name Data, passed by value
    • Argument datatype Blob

  3. Add code to the InternetData function
    that processes the returned HTML as appropriate. This example simply
    displays the HTML in a MessageBox:

Secure Sockets Layer service

PowerBuilder allows you to establish Secure Sockets Layer
(SSL) connections to EAServer.
The SSL protocol allows connections to be secured using public-key
encryption and authentication algorithms that are based on digital certificates.
SSL is a “wrapper” protocol: packets for another protocol are secured
by embedding them inside SSL packets. For example, HTTPS is HTTP secured
by embedding each HTTP packet within an SSL packet. Likewise, IIOPS
is IIOP embedded within SSL.

You use an instance of the SSLServiceProvider object to establish
the connection from the client to the server. For more information,
see the PowerScript Reference
and Chapter 25, “Using SSL in PowerBuilder clients.”

Transaction server service

Use the transaction server service to access information about
the context of an object running in a transaction server such as EAServer. You can use the TransactionServer
object to influence transaction behavior programmatically, and to
access the methods of another component on the transaction server.

For more information, see Chapter 23, “Building an EAServer Component.”

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Powerbuilder Documentation 11.5
PB Docs 115 Powerbuilder Application Techniques Powerbuilder Documentation Powerbuilder Documentation 11.5 Powerbuilder Documentation Older
August 3, 2023
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