Updates field contents of a AbstractValidatableColumn

ValidatableFieldUpdater

import java.util.Set;

import javax.validation.ConstraintViolation;

import org.spp.im.mui.gwt.client.module.common.widget.grid.ValidatableInputCell.ValidationData;
import org.spp.im.mui.gwt.shared.i18n.UiMessages;

import com.google.gwt.cell.client.FieldUpdater;
import com.google.gwt.user.cellview.client.AbstractHasData;
import com.google.gwt.view.client.ProvidesKey;


/**
 * Encapsulates logic for validating then updating a row-column value.
 * @author cphillipson
 *
 * @param <T> the type
 * @param <O> the owning type of the field to be validated; in many cases T may have only primitive or wrapper types, therefore O could be the same type as T
 */
final class ValidatableFieldUpdater<T, O> implements FieldUpdater<T, String> {

    private final AbstractHasData<T> table;
    private final AbstractValidatableColumn<T, O> column;

    ValidatableFieldUpdater(AbstractHasData<T> table, AbstractValidatableColumn<T, O> column) {
        this.table = table;
        this.column = column;
    }

    @Override
    public void update(int index, T dto, String newValue) {
        final ValidatableInputCell cell = column.getCell();
        final ConversionResult cr = column.attemptValueConversion(newValue);
        final ProvidesKey<T> keyProvider = table.getKeyProvider();
        final ValidationData viewData =  cell.getViewData(keyProvider.getKey(dto));
        if (cr.wasConvertedSuccessfully()) {
            final Set<ConstraintViolation<O>> violations = column.validate(cr.getValue());
            if (!violations.isEmpty()) {  // invalid
                final StringBuffer errorMessage = new StringBuffer();
                for (final ConstraintViolation<O> constraintViolation : violations) {
                    errorMessage.append(constraintViolation.getMessage());
                }
                viewData.setInvalid(true);
                cell.setErrorMessage(errorMessage.toString());
                table.redraw();
            } else {  // valid
                viewData.setInvalid(false);
                cell.setErrorMessage("");
                column.doUpdate(index, dto, newValue);
            }
        } else { // conversion exception
            viewData.setInvalid(true);
            cell.setErrorMessage(UiMessages.INSTANCE.improper_input_format());
        }
    }
}