3 Oracle COM Automation Feature Core Functionality

Data Type Conversion for PL/SQL

Table 3-1 shows the mapping between PL/SQL data types and COM Automation data types.

This guide follows a convention where COM Automation data types are prefaced by an initial p when used as IN OUT or OUT parameters. Data types without the initial p are IN parameters.

Data Type Conversion for Java

Table 3-2 lists the supported COM Automation data types and related mappings to Java data types.

All data type mapping applies to properties, arguments, and return values, except void, which applies only to return values.

PL/SQL Use of HRESULT

The PL/SQL APIs return an integer return code. The return code is 0 when successful, or a nonzero value of HRESULT when an error occurs.

Java Use of HRESULT

In the Java API, HRESULT is a data member of the COMException class.

Information Required for COM Objects

Review the following information about the COM objects that you intend to use:

• You must determine the Program ID of the COM object. The Program ID, or progID, is a descriptive string that maps to the globally unique identifier (GUID), a hexadecimal number that uniquely identifies a COM object.

  The following string is an example of a progID:

  Excel.Worksheet.1
  
  

  Use the progID with the API that instantiates the COM object.

• You must be aware of the types of properties and methods that are exposed through the COM object's IDispatch interface. Usually, the ISV provides documentation describing the names and data type of the object's properties and the prototypes of the object's methods. Properties are referred to by a descriptive string, such as xpos or ypos. A property can be any standard COM Automation data type, such as INT or BSTR. The GetProperty and SetProperty APIs take the property name and a variable of the appropriate data type. Methods are referred to by a descriptive string, such as InsertChart. A method takes a set of parameters that are of different COM Automation data types and returns a COM Automation data type.

  The following is an example of a COM Automation method prototype in COM Interface Definition Language (IDL) grammar:

  [id(0x6003000)]
  long Post([in, out] long* lngAccountNo,
            [in, out] long* lngAmount,
            [in, out] BSTR* strResult);
  
  

  Interfaces define object methods and properties. COM IDL is used to specify interfaces that are defined on COM objects.

OLE/COM Object Viewer

Microsoft provides a tool called the OLE/COM Object Viewer with Microsoft Visual Studio for browsing the properties and methods of COM objects on a local system. This tool enables you to quickly and easily determine the properties and methods that each COM object exposes. See Figure 3-1 for an example.

Figure 3-1 OLE/COM Object Viewer

Description of "Figure 3-1 OLE/COM Object Viewer"

Using COM Automation Feature APIs

In a typical use of Oracle COM Automation Feature, you design a Java class or PL/SQL block to create and manipulate a COM object. The class or code block performs the following steps:

1. Creates the COM object as follows:

   • In PL/SQL, using CreateObject

   • In Java, using a constructor or the Create method

2. Manipulates the COM object calling the following APIs:

   • GetProperty to get a property value

   • SetProperty to set a property value to a new value

3. Calls Invoke to call a method

   To prepare for the Invoke call, you use InitArg and SetArg to package the argument to be sent to the COM Automation method.

4. Calls GetLastError in PL/SQL to get the most recent error information

5. Destroys the object using DestroyObject in PL/SQL or Destroy in Java

PL/SQL APIs

Oracle COM Automation Feature externalizes the following APIs for PL/SQL development:

• CreateObject

• DestroyObject

• GetLastError

• GetProperty

• SetProperty

• InitArg

• InitOutArg

• GetArg

• SetArg

• Invoke

Java APIs

Oracle COM Automation Feature externalizes the following APIs for Java development:

• Automation Constructor

• Automation Methods

  • Create

  • Destroy

  • GetProperty

  • SetProperty

  • InitArg

  • SetArg

  • Invoke

• Currency Constructor

• Currency Methods

  • Get

  • Set

CreateObject

This API instantiates a COM object in a COM Automation server.

Syntax

FUNCTION CreateObject(progid VARCHAR2, reserved BINARY_INTEGER, servername VARCHAR2, objecttoken OUT BINARY_INTEGER) RETURN BINARY_INTEGER;

Remarks

The created COM Automation object is freed with a corresponding call to DestroyObject. This nullifies the internal representation of the object in the Oracle COM Automation Feature and releases all interfaces associated with the object.

This funtion returns 0 when successful, or a nonzero value for HRESULT when an error occurs.

Code Sample

HRESULT BINARY_INTEGER;
applicationToken BINARY_INTEGER:=-1;

HRESULT :=ORDCOM.CreateObject('Excel.Application', 0, '', applicationToken);
IF (HRESULT!=0) THEN
  dbms_output.put_line(HRESULT);
END IF;

DestroyObject

This API destroys a created COM Automation object.

Syntax

FUNCTION DestroyObject(objecttoken BINARY_INTEGER) RETURN BINARY_INTEGER;

Remarks

Calling DestroyObject nullifies the internal representation of the object in the Oracle COM Automation Feature and releases all interfaces associated with the object.

This function returns 0 when successful, or a nonzero value of HRESULT when an error occurs.

Code Sample

HRESULT BINARY_INTEGER;
applicationToken BINARY_INTEGER:=-1;

/* Assume applicationToken is initialized. */

HRESULT:=ORDCOM.DestroyObject(applicationToken);
IF (HRESULT!=0) THEN
   dbms_output.put_line(HRESULT);

GetLastError

This API obtains the COM Automation error information about the last error that occurred.

Syntax

FUNCTION GetLastError(source OUT VARCHAR2, description OUT VARCHAR2, helpfile OUT VARCHAR2, helpid OUT BINARY_INTEGER) RETURN BINARY_INTEGER;

Remarks

Each call to an Oracle COM Automation Feature API (except GetLastError) resets the error information, so that GetLastError obtains error information only for the most recent Oracle COM Automation Feature API call. Because GetLastError does not reset the last error information, it can be called multiple times to get the same error information.

This funtion returns 0 when successful, or a nonzero value of HRESULT when an error occurs.

See "Microsoft COM Automation Errors" for a description of the types of errors that can be returned by this function.

Code Sample

HRESULT BINARY_INTEGER;
applicationToken BINARY_INTEGER:=-1;
error_src VARCHAR2(255);
error_description VARCHAR2(255);
error_helpfile VARCHAR2(255);
error_helpID BINARY_INTEGER;

HRESULT:=ORDCOM.CreateObject('Excel.Application', 0, '', applicationToken);
IF (HRESULT!=0) THEN
  ORDCOM.GetLastError(error_src, error_description, error_helpfile, 
      error_helpID);
  dbms_output.put_line(error_src);
  dbms_output.put_line(error_description);

  dbms_output.put_line(error_helpfile);
END IF;

GetProperty

This API returns the property value of a COM Automation object.

Syntax

FUNCTION GetProperty(objecttoken BINARY_INTEGER, propertyname VARCHAR2, argcount BINARY_INTEGER, propertyvalue OUT any_PL/SQL_data type) RETURN BINARY_INTEGER;

Remarks

If the property returns a COM object, then you must specify a local variable of data type BINARY_INTEGER for the propertyvalue parameter. An object token is stored in the local variable, and this object token can be used with other COM Automation stored procedures.

When the property returns an array, if propertyvalue is specified, then it is set to NULL.

This function returns 0 when successful, or a nonzero value of HRESULT when an error occurs.

Code Sample

/*
 * This is an excerpt from a Microsoft Excel application.
 */

HRESULT BINARY_INTEGER;
ChartObject BINARY_INTEGER := -1;
ChartToken BINARY_INTEGER := -1;

/* Assume ChartObject is initialized. */

HRESULT := ORDCOM.GetProperty(ChartObject, 'Chart', 0, ChartToken);
IF (HRESULT!=0) THEN    
  dbms_output.put_line(HRESULT);
END IF;

SetProperty

This API sets a property of a COM Automation object to a new value.

Syntax

FUNCTION SetProperty(objecttoken BINARY_INTEGER, propertyname VARCHAR2, newvalue any_PL/SQL_data type, data type VARCHAR2) RETURN BINARY_INTEGER;

Remarks

This function returns a 0 when successful, or a nonzero value of HRESULT when an error occurs.

Code Sample

/*
 * This is an excerpt from a Microsoft Excel application.
 */

HRESULT BINARY_INTEGER;
RangeToken BINARY_INTEGER := -1;

/* Assume RangeToken is initialized. */

HRESULT := ORDCOM.SetProperty(RangeToken, 'Value', 'EmpNo', 'BSTR');
IF (HRESULT!=0) THEN    
  dbms_output.put_line(HRESULT);
END IF;

InitArg

This API initializes the parameter set passed to an Invoke call.

Syntax

PROCEDURE InitArg();

Remarks

The InitArg call initializes the parameter set. After InitArg has been called, a SetArg call sets the first parameter to the specified value. A second SetArg call sets the second parameter in the parameter list. Subsequent calls set the nth parameters in the parameter list, where n is the number of times SetArg has been called after an InitArg call. Another call to InitArg resets the argument list and a call to SetArg sets the first parameter again.

Code Sample

See "Invoke" for sample code.

InitOutArg

InitOutArg must be called after a COM method is invoked in preparation for getting the values of OUT and IN OUT parameters using GetArg. After calling InitOutArg, the first call to GetArg gets the value for the first OUT or IN OUT parameter, the second call to GetArg gets the value for the second OUT or IN OUT parameters, and so on. Calling InitOutArg again restarts this process.

Syntax

PROCEDURE InitOutArg();

Remarks

See the section on SetArg data type strings in "SetArg" for information about IN and OUT parameters.

Code Sample

See "Invoke" for sample code.

GetArg

Gets the argument of OUT and IN OUT parameters after the COM method has been invoked.

Syntax

PROCEDURE GetArg(data OUT any_PL/SQL_data type, type VARCHAR2);

Remarks

See the section on SetArg data type strings in "SetArg" for information about IN and OUT parameters.

Code Sample

See "Invoke" for sample code.

SetArg

Used to construct the parameter list for the next Invoke call.

SetArg sets a parameter's value to be passed by value.

Syntax

PROCEDURE SetArg(paramvalue any_PL/SQL_data type, data type VARCHAR2);

Remarks

Each SetArg procedure sets the nth parameter value. The InitArg call initializes the parameter set. After InitArg has been called, a SetArg call sets the first parameter to the specified value. A second SetArg call sets the second parameter in the parameter list. Subsequent calls set the nth parameters in the parameter list, where n is the number of times SetArg has been called after an InitArg call. Another call to InitArg resets the argument list and a call to SetArg sets the first parameter again.

Data types without the initial p are IN parameters. Those data types prefaced by an initial p are IN OUT or OUT parameters.

Code Sample

See "Invoke" for sample code.

Invoke

This API calls a method of a COM Automation object. This function uses the parameter list, previously created by the calls to InitArg and SetArg as input for the COM Automation method.

Syntax

FUNCTION Invoke(objecttoken BINARY_INTEGER, methodname VARCHAR2, argcount BINARY_INTEGER, returnvalue OUT any_PL/SQL_data type) RETURN BINARY_INTEGER;

Remarks

If the return value of the function is a COM object, then the developer must specify a local variable of data type BINARY_INTEGER for the returnvalue parameter. An object token is stored in the local variable, and this object token can be used with other Oracle COM Automation Feature APIs.

This function returns 0 when successful, or a nonzero value of HRESULT when an error occurs.

Code Sample

/*
* Following is the IDL definition of the COM Automation method
* being called:
*
* HRESULT TestOutArg([in, out] short *x1,
* [in] short x2,
* [out] short *x3,
* [out, retval] short *x4);
*/

HRESULT BINARY_INTEGER := -1;
applicationToken BINARY_INTEGER := -1;
x1 DOUBLE PRECISION := 12;
x2 DOUBLE PRECISION := 7;
x3 DOUBLE PRECISION := 0;
x4 DOUBLE PRECISION := 0;

/* Assume applicationToken is initialized. */

ORDCOM.InitArg();
ORDCOM.SetArg(x1, 'pI2');
ORDCOM.SetArg(x2, 'I2');
ORDCOM.SetArg(x3, 'pI2');

HRESULT := ORDCOM.Invoke(applicationToken, 'TestOutArg', 3, x4);
IF (HRESULT!=0) THEN    
  dbms_output.put_line(HRESULT);
END IF;

ORDCOM.InitOutArg();
ORDCOM.GetArg(x1, 'pI2');
ORDCOM.GetArg(x3, 'pI2');

Automation Constructor

This API creates a COM object.

Syntax

public Automation()
        public Automation(String progID)
        public Automation(String progID, String serverName)

Remarks

The default constructor public Automation() does nothing. It is used with a Create method.

Using a constructor that takes only the progID parameter forces Oracle COM Automation Feature to check the registry for the location of the COM object. Registry information indicates whether the COM object is local or remote.

COM Automation objects created using the nondefault constructors are freed with a corresponding call to Destroy. This nullifies the internal representation of the objects in Oracle COM Automation Feature and releases all interfaces associated with the objects.

Oracle COM Automation Feature for Java does not allow in-process COM Automation servers. Developers can use dllhost to support in-process servers.

The COMException exception is thrown if an error occurs.

Code Sample

The following code sample demonstrates the nondefault constructors.

// Use the registry to determine where to create the COM object.
   Automation word = new Automation("Word.Basic");

   // Create the COM object on the specified server.
   Automation excel = new Automation("Excel.Application", 
                                     "\\ServerName");

   // Free the COM objects.
   word.Destroy();
   excel.Destroy();

Create

This API instantiates a COM object in a COM Automation server.

Syntax

public void Create(String progID)
public void Create(String progID, String serverName)

Remarks

The COM Automation object created with the Create method is freed with a corresponding call to Destroy. This nullifies the internal representation of the object in Oracle COM Automation Feature and releases all interfaces associated with the object.

Using the constructor that takes only the progID parameter forces Oracle COM Automation Feature to check the registry for the location of the COM object. Registry information indicates whether the COM object is local or remote.

Oracle COM Automation Feature for Java does not allow in-process COM Automation servers. Developers can use dllhost to support in-process servers.

The COMException exception is thrown if an error occurs.

Code Sample

// Use the default constructor.
   Automation word = new Automation();
   Automation excel = new Automation();

   // Use the registry to determine where to create the COM object.
   word.Create("Word.Basic");

   // Create the COM object on the specified server system.
   excel.Create("Excel.Application", "\\ServerName");

   // Free the COM objects.
   word.Destroy();
   excel.Destroy();

Destroy

This API destroys a created COM Automation object.

Syntax

public void Destroy()

Remarks

Calling Destroy nullifies the internal representation of the object in the Oracle COM Automation Feature and releases all interfaces associated with the object.

Code Sample

See "Create" for code sample.

GetProperty

This API gets a property value of a COM Automation object.

Syntax

public allowed_type GetProperty(String propName, allowed_type[] propVal)

Remarks

If the property is a COM object, then it can be retrieved using the allowed_type of oracle.win.com.Automation. The Automation Java object that is returned can be used to get and set properties and call methods on the property.

GetProperty uses an array parameter to return the property value to overload the GetProperty method. Overloading would not be possible if the property value were returned as a return value. The array solves the problem caused by Java not having an out parameter.

The property is still returned as a return value for convenience.

The COMException exception is thrown if an error occurs.

Code Sample

// A Microsoft Excel ChartObject object.
   Automation chartObject = null;
   // A Microsoft Excel Chart object.
   Automation chart = null;
   // Used for properties of type Automation.
   Automation[] autoProp = { null };

   // Assume the Microsoft Excel ChartObject object is initialized.

   // Get the Chart property.
   chartObject.GetProperty("Chart", autoProp);
   chart = autoProp[0];

   // Set the Chart property.
   chartObject.SetProperty("Chart", chart);

SetProperty

This API sets a property of a COM Automation object to a new value.

Syntax

public void SetProperty(String propName, allowed_type propVal)

Remarks

If the property is a COM object, it can be set using the allowed type of oracle.win.com.Automation. The property value must be a valid Automation Java object.

The COMException exception is thrown if an error occurs.

Code Sample

See "GetProperty" for sample code.

InitArg

This API initializes the parameter set passed to an Invoke call.

Syntax

public void InitArg()

Remarks

The InitArg call initializes the parameter set and must be called even if the COM method does not take any parameters. After InitArg has been called, a SetArg call sets the first parameter to the specified value. A second SetArg call sets the second parameter in the parameter list. Subsequent calls set the nth parameters in the parameter list, where n is the number of times SetArg has been called after an InitArg call. Another call to InitArg resets the argument list and a call to SetArg sets the first parameter again.

Code Sample

See "Invoke" for sample code.

SetArg

This API is used to construct the parameter list for the next Invoke call.

Syntax

public void SetArg(allowed_type val)

Remarks

If a parameter is a COM object, then the allowed_type of the corresponding argument should be oracle.win.com.Automation. The argument should be a valid Automation Java object.

No exceptions are thrown at this time. However, if an error occurs, for example, if the wrong argument type is passed, then it will be caught when the Invoke method is called.

Code Sample

See "Invoke" for sample code.

Invoke

Calls a method of a COM Automation object. This function uses the parameter list, previously created by the calls to InitArg and SetArg, as input for the COM Automation method.

Syntax

public void Invoke(String methodName, allowed_type[] retVal)
public void Invoke(String methodName)

Remarks

If the COM method returns a COM object as the return value, then the allowed_type of the return value is oracle.win.com.Automation. The Automation Java object that is returned can be used to get and set properties, and call methods on the return value.

To overload the Invoke method, Invoke uses an array parameter to return the values of COM object methods. Overloading would not be possible if the property value was returned as a return value. The array solves the problem caused by Java not having an out parameter.

The version of Invoke that takes only one parameter, public void Invoke(String methodName), is used for COM object methods with void return types.

The property is still returned as a return value for convenience.

The COMException exception is thrown if an error occurs.

Code Sample

// A Microsoft Excel Worksheet object.
   Automation workSheet = null;
   // A Microsoft Excel ChartObjects collection object.
   Automation chartObjects = null;
   // A Microsoft Excel ChartObject object.
   Automation chartObject = null;
   // Used for return values of type Automation.
   Automation[] autorv = { null };
   // Dimensions for a Microsoft Excel ChartObject object.
   short xpos = 100, ypos = 30, width = 400, height = 250;

   // Assume the Microsoft Excel Worksheet object is initialized.

   // Invoke a method that takes no arguments.
   workSheet.InitArg();
   workSheet.Invoke("ChartObjects", autorv);
   chartObjects = autorv[0];
   
   // Invoke a method that takes multiple arguments.
   chartObjects.InitArg();
   chartObjects.SetArg(xpos);
   chartObjects.SetArg(ypos);
   chartObjects.SetArg(width);
   chartObjects.SetArg(height);
   chartObjects.Invoke("Add", autorv);
   chartObject = autorv[0];

Currency Constructor

This API creates a currency Java object.

Syntax

public Currency(long value)

Get

This API gets the 8-byte CURRENCY number.

Syntax

public long Get()

Remarks

Returns the 8-byte CURRENCY number.

Set

This API sets the 8-byte CURRENCY number.

Syntax

public void Set(long value)