Parsing JBehave tables

This is a simple sample how to parse JBehave tables.

In our project we often have to parse JBehave tables that might look like this one:

Given currencies are truncated to these decimal places
| Currency | Decimal places |
|   USD    |       2        |
|   JPY    |       0        |
|   LYD    |       3        |

The standard approach is to write something like this

    @Given("currencies are truncated to these decimal places $currencyDecimalPlaces")
    public void currencyDecimalPlaces(ExamplesTable currencyDecimalPlacesTable) {
        ...
        for (Parameters row : currencyDecimalPlacesTable.getRowsAsParameters()) {
            // read row data            
        }
        ...
    }                   

where reading row data may look like this:

            CurrencyCode currencyCode = row.valueAs("Currency", CurrencyCode.class);
            Integer decimalPlaces = row.valueAs("Decimal places", Integer.class);

or we can make it a little more readable like this:

            CurrencyCode currencyCode = Currency.in(row);
            Integer decimalPlaces = DecimalPlaces.in(row);

To make the readable code we define a new Column class:

public class Column<T> {

    private final String label;
    private final Class<T> defaultType;


    public Column(String label, Class<T> defaultType) {
        this.label = label;
        this.defaultType = defaultType;
    }


    public <T> T in(Parameters row, Class<T> type) {
        return row.valueAs(label, type);
    }


    public T in(Parameters row) {
        return in(row, defaultType);
    }


    public String asString(Parameters row) {
        return in(row, String.class);
    }


    public static <T> Column<T> column(String label, Class<T> defaultType) {
        return new Column<T>(label, defaultType);
    }


    public static Column<String> column(String label) {
        return new Column<String>(label, String.class);
    }
}

and registering custom columns:

public interface Columns {

    ...
    
    public static final Column<CurrencyCode> Currency = column("Currency", CurrencyCode.class);
    public static final Column<Integer> DecimalPlaces = column("Decimal places", Integer.class);
    
    ...
}   

now we can convert the column to the default registered class

    CurrencyCode currencyCode = Currency.in(row);

or to a specified class:

    String currencyCode = Currency.in(row, String.class);