vaadin-framework/documentation/articles/FormattingDataInGrid.asciidoc

---
title: Formatting Data In Grid
order: 24
layout: page
---

[[formatting-data-in-grid]]
= Formatting data in grid

Without any special configuration, Grid tries to find a `Converter` for
converting the property value into a String that can be shown in the
browser. The `ConverterFactory` configured for the session is used for
this purpose. If no compatible converter is found, Grid will instead
fall back to using `toString()` on the property value.

[[cellstylegenerator]]
CellStyleGenerator
^^^^^^^^^^^^^^^^^^

Grid does also provide a couple of mechanisms for fine-tuning how the
data is displayed. The simplest way of controlling the data output is to
use a `CellStyleGenerator` to add custom stylenames to individual cells,
thus affecting which CSS rules from the theme are applied to each cell.

[source,java]
....
grid.setCellStyleGenerator(new CellStyleGenerator() {
  @Override
  public String getStyle(CellReference cellReference) {
    if ("amount".equals(cellReference.getPropertyId())) {
      Double value = (Double) cellReference.getValue();
      if (value.doubleValue() == Math.round(value.doubleValue())) {
        return "integer";
      }
    }
    return null;
  }
});

getPage().getStyles().add(".integer { color: blue; }");
....

We have not yet defined any `Converter` or `Renderer` in this example. This
means that Grid will use a `StringToDoubleConverter` to convert the Double
values from the data source into Strings that are sent to the browser
and displayed in each cell.

To keep this example as simple as possible, we are dynamically injecting
new CSS styles into the page. In a real application, it's recommended to
instead add the styles to the theme since that helps with separation of
concerns.

[[renderer]]
Renderer
^^^^^^^^

The next thing you can do to control how the data is displayed is to use
a `Renderer`. The `Renderer` will receive the value from the data source
property, possibly after it has been converted to the `Renderer`{empty}'s input
type using a `Converter`. The `Renderer` is will then make sure the value
gets show in an appropriate way in the browser. A simple renderer might
just show the data as text, but there are also more complex `Renderer`{empty}s
that e.g. show a numerical value as a progress bar.

Will will use a `NumberRenderer` using a currency format to render the
cell values for the `Amount` column. To do this, we simply create and
configure it and then set it as the `Renderer` for the designated column.
No `Converter` will be used in this case since `NumberRenderer` already
knows ho to handle values of the type Double.

[source,java]
....
NumberFormat poundformat = NumberFormat.getCurrencyInstance(Locale.UK);
NumberRenderer poundRenderer = new NumberRenderer(poundformat);
grid.getColumn("amount").setRenderer(poundRenderer);
....

[[converter]]
Converter
^^^^^^^^^

The last way of controlling how data is displayed is to use a `Converter`.
The framework will in most cases find and use a suitable `Converter`, but
you can also supply your own if the default conversion is not what you
need. The following example uses a custom `Converter` for the `Count` column
to change the value into HTML strings with different HTML for even and
odd counts. Grid will by default protect you from cross-site scripting
vulnerabilities by not interpreting HTML in cell values. This can be
overridden by setting the column to use a `HtmlRenderer` instead of the
default `TextRenderer`. Both those renderers expect String values. Since
we will not be editing any values, the Converter doesn't need to support
changing the HTML strings back into integers.

[source,java]
....
grid.getColumn("count").setConverter(new StringToIntegerConverter() {
  @Override
  public String convertToPresentation(Integer value, Class<? extends String> targetType, Locale locale)
      throws Converter.ConversionException {
    String stringRepresentation = super.convertToPresentation(value, targetType, locale);
    if (value.intValue() % 2 == 0) {
      return "<strong>" + stringRepresentation + "</strong>";
    } else {
      return "<em>" + stringRepresentation + "</em>";
    }
  }
});

grid.getColumn("count").setRenderer(new HtmlRenderer());
....

[[full-example]]
Full example
^^^^^^^^^^^^

Putting all these pieces together, we end up with this class that uses
the same data as in the <<UsingGridWithAContainer#using-with-a-container,Using
Grid with a Container>> example.

[source,java]
....
import java.text.NumberFormat;
import java.util.Locale;

import com.vaadin.annotations.Theme;
import com.vaadin.data.util.converter.Converter;
import com.vaadin.data.util.converter.StringToIntegerConverter;
import com.vaadin.server.VaadinRequest;
import com.vaadin.ui.Grid;
import com.vaadin.ui.Grid.CellReference;
import com.vaadin.ui.Grid.CellStyleGenerator;
import com.vaadin.ui.UI;
import com.vaadin.ui.renderers.HtmlRenderer;
import com.vaadin.ui.renderers.NumberRenderer;

@Theme("valo")
public class FormattingDataInGrid extends UI {

  @Override
  protected void init(VaadinRequest request) {
    Grid grid = new Grid(GridExampleHelper.createContainer());

    setContent(grid);

    grid.setCellStyleGenerator(new CellStyleGenerator() {
      @Override
      public String getStyle(CellReference cellReference) {
        if ("amount".equals(cellReference.getPropertyId())) {
          Double value = (Double) cellReference.getValue();
          if (value.doubleValue() == Math.round(value.doubleValue())) {
            return "integer";
          }
        }
        return null;
      }
    });

    getPage().getStyles().add(".integer { color: blue; }");

    NumberFormat poundformat = NumberFormat.getCurrencyInstance(Locale.UK);
    NumberRenderer poundRenderer = new NumberRenderer(poundformat);
    grid.getColumn("amount").setRenderer(poundRenderer);

    grid.getColumn("count").setConverter(new StringToIntegerConverter() {
      @Override
      public String convertToPresentation(Integer value,
            Class<? extends String> targetType, Locale locale)
            throws Converter.ConversionException {
        String stringRepresentation = super.convertToPresentation(
            value, targetType, locale);
        if (value.intValue() % 2 == 0) {
          return "<strong>" + stringRepresentation + "</strong>";
        } else {
          return "<em>" + stringRepresentation + "</em>";
        }
      }
    });

    grid.getColumn("count").setRenderer(new HtmlRenderer());
  }
}
....