The custom publisher (custom class) mechanism can be used for the following purposes:

• formatting or inserting data to the request before publishing
• taking full control of the publishing

Sample Custom Publisher for Inserting Data

Consider a scenario where you need to pass data that is not captured on the form or data is not provided by the customer when filling the form. Let's take the earlier example provided for database request where Credit Card details such as Card Number, Current Balance, Currency, Card Type and Minimum Payment are to be entered. Let's assume that data for Currency is not provided by the customer. However, you would like to pass the value for Currency in the request and publish the updated value to the database. You can achieve this using the custom publisher class as shown in the code sample:
/* This is a sample custom publisher Java class that inserts a value for Currency column, which is not entered on the form by the customer. */
import java.util.ArrayList;
import java.util.HashMap;
import com.intellectdesign.canvas.model.StateModelException;
import com.intellectdesign.canvas.reqmodel.external.CanvasPublishContext;
import com.intellectdesign.canvas.reqmodel.external.CanvasReqModelDBPublisher;
/* In this example, the form data is to be sent to database, hence the
custom publisher class must be extended from CanvasReqModelDBPublisher class. */
public class CustomPublisher extends CanvasReqModelDBPublisher
{
/* The prepareDataToBePublished method prepares the data to be sent
to the database and can be used for any data manipulation or
formatting needs. */
@Override
public void prepareDataToBePublished(CanvasPublishContext publishContext) throws StateModelException
{
super.prepareDataToBePublished(publishContext);
// Form data is stored in an array list.
ArrayList data = (ArrayList) publishContext.getFormattedData();
/* Two array list variables are used to store field IDs
and field values separately. */
ArrayList columnList, valueList;
columnList =(ArrayList) ((HashMap)data.get(0)).get("COLUMN_IDS");
valueList =(ArrayList) ((HashMap)data.get(0)).get("VALUES");
/* The getUserData method fetches the user details such as
GCIF, user ID, first/last name etc. */
publishContext.getUserData();
/* The index number of the Currency field in the
array list is stored in a variable. */
int ind = columnList.indexOf("CURRENCY");
/* The current value of the field is removed and
new value is assigned to it. */
valueList.remove(ind);
valueList.add(ind,"USD");
/* The setFormattedData method sets the data
in the CanvasPublishContext object. */
publishContext.setFormattedData(data);
}
/* The publish method publishes the formatted data
in the CanvasPublishContext object to the database. */
@Override
public boolean publish(CanvasPublishContext publishContext) throws StateModelException
{
return super.publish(publishContext);
}
}