Adds a textual null representation to Grid renderers(#16560)7.5.0.beta2

Adds an optional textual value for null to Grid.AbstractRenderer

Change-Id: I4998476308e4259306f1774f309968520d8672e5

11 files changed, 357 insertions, 95 deletions

diff --git a/server/src/com/vaadin/ui/Grid.java b/server/src/com/vaadin/ui/Grid.java
index 2c7e63ddf8..73d3a91176 100644
--- a/server/src/com/vaadin/ui/Grid.java
+++ b/server/src/com/vaadin/ui/Grid.java
@@ -3286,8 +3286,15 @@ public class Grid extends AbstractComponent implements SelectionNotifier,
 
         private final Class<T> presentationType;
 
-        protected AbstractRenderer(Class<T> presentationType) {
+        private final String nullRepresentation;
+
+        protected AbstractRenderer(Class<T> presentationType, String nullRepresentation) {
             this.presentationType = presentationType;
+            this.nullRepresentation = nullRepresentation;
+        }
+
+        protected AbstractRenderer(Class<T> presentationType) {
+            this(presentationType, null);
         }
 
         /**
@@ -3317,7 +3324,19 @@ public class Grid extends AbstractComponent implements SelectionNotifier,
 
         @Override
         public JsonValue encode(T value) {
-            return encode(value, getPresentationType());
+            if (value == null) {
+                return encode(getNullRepresentation(), String.class);
+            } else {
+                return encode(value, getPresentationType());
+            }
+        }
+
+        /**
+         * Null representation for the renderer
+         * @return a textual representation of {@code null}
+         */
+        protected String getNullRepresentation() {
+            return nullRepresentation;
         }
 
         /**
diff --git a/server/src/com/vaadin/ui/renderers/AbstractJavaScriptRenderer.java b/server/src/com/vaadin/ui/renderers/AbstractJavaScriptRenderer.java
index bed34cf6e3..104e07f02f 100644
--- a/server/src/com/vaadin/ui/renderers/AbstractJavaScriptRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/AbstractJavaScriptRenderer.java
@@ -105,8 +105,12 @@ public abstract class AbstractJavaScriptRenderer<T> extends AbstractRenderer<T>
     private JavaScriptCallbackHelper callbackHelper = new JavaScriptCallbackHelper(
             this);
 
+    protected AbstractJavaScriptRenderer(Class<T> presentationType, String nullRepresentation) {
+        super(presentationType, nullRepresentation);
+    }
+
     protected AbstractJavaScriptRenderer(Class<T> presentationType) {
-        super(presentationType);
+        super(presentationType, null);
     }
 
     @Override
diff --git a/server/src/com/vaadin/ui/renderers/ButtonRenderer.java b/server/src/com/vaadin/ui/renderers/ButtonRenderer.java
index 0b070d3f69..a747e45713 100644
--- a/server/src/com/vaadin/ui/renderers/ButtonRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/ButtonRenderer.java
@@ -15,6 +15,8 @@
  */
 package com.vaadin.ui.renderers;
 
+import elemental.json.JsonValue;
+
 /**
  * A Renderer that displays a button with a textual caption. The value of the
  * corresponding property is used as the caption. Click listeners can be added
@@ -27,9 +29,12 @@ public class ButtonRenderer extends ClickableRenderer<String> {
 
     /**
      * Creates a new button renderer.
+     *
+     * @param nullRepresentation
+     *            the textual representation of {@code null} value
      */
-    public ButtonRenderer() {
-        super(String.class);
+    public ButtonRenderer(String nullRepresentation) {
+        super(String.class, nullRepresentation);
     }
 
     /**
@@ -37,9 +42,34 @@ public class ButtonRenderer extends ClickableRenderer<String> {
      * 
      * @param listener
      *            the click listener to register
+     * @param nullRepresentation
+     *            the textual representation of {@code null} value
      */
-    public ButtonRenderer(RendererClickListener listener) {
-        this();
+    public ButtonRenderer(RendererClickListener listener, String nullRepresentation) {
+        this(nullRepresentation);
         addClickListener(listener);
     }
+
+    /**
+     * Creates a new button renderer.
+     */
+    public ButtonRenderer() {
+        this("");
+    }
+
+    /**
+     * Creates a new button renderer and adds the given click listener to it.
+     *
+     * @param listener
+     *            the click listener to register
+     */
+    public ButtonRenderer(RendererClickListener listener) {
+        this(listener, "");
+    }
+
+    @Override
+    public String getNullRepresentation() {
+        return super.getNullRepresentation();
+    }
+
 }
diff --git a/server/src/com/vaadin/ui/renderers/ClickableRenderer.java b/server/src/com/vaadin/ui/renderers/ClickableRenderer.java
index 38e9acef9c..01e939bb67 100644
--- a/server/src/com/vaadin/ui/renderers/ClickableRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/ClickableRenderer.java
@@ -103,7 +103,11 @@ public class ClickableRenderer<T> extends AbstractRenderer<T> {
     }
 
     protected ClickableRenderer(Class<T> presentationType) {
-        super(presentationType);
+        this(presentationType, null);
+    }
+
+    protected ClickableRenderer(Class<T> presentationType, String nullRepresentation) {
+        super(presentationType, nullRepresentation);
         registerRpc(new RendererClickRpc() {
             @Override
             public void click(String rowKey, String columnId,
diff --git a/server/src/com/vaadin/ui/renderers/DateRenderer.java b/server/src/com/vaadin/ui/renderers/DateRenderer.java
index 9dd4d19e87..092b3f405e 100644
--- a/server/src/com/vaadin/ui/renderers/DateRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/DateRenderer.java
@@ -41,7 +41,7 @@ public class DateRenderer extends AbstractRenderer<Date> {
      * representation for the default locale.
      */
     public DateRenderer() {
-        this(Locale.getDefault());
+        this(Locale.getDefault(), "");
     }
 
     /**
@@ -56,7 +56,24 @@ public class DateRenderer extends AbstractRenderer<Date> {
      *             if {@code locale} is {@code null}
      */
     public DateRenderer(Locale locale) throws IllegalArgumentException {
-        this("%s", locale);
+        this("%s", locale, "");
+    }
+
+    /**
+     * Creates a new date renderer.
+     * <p>
+     * The renderer is configured to render with the {@link Date#toString()}
+     * representation for the given locale.
+     *
+     * @param locale
+     *            the locale in which to present dates
+     * @param nullRepresentation
+     *            the textual representation of {@code null} value
+     * @throws IllegalArgumentException
+     *             if {@code locale} is {@code null}
+     */
+    public DateRenderer(Locale locale, String nullRepresentation) throws IllegalArgumentException {
+        this("%s", locale, nullRepresentation);
     }
 
     /**
@@ -74,7 +91,27 @@ public class DateRenderer extends AbstractRenderer<Date> {
      *      String Syntax</a>
      */
     public DateRenderer(String formatString) throws IllegalArgumentException {
-        this(formatString, Locale.getDefault());
+        this(formatString, "");
+    }
+
+    /**
+     * Creates a new date renderer.
+     * <p>
+     * The renderer is configured to render with the given string format, as
+     * displayed in the default locale.
+     *
+     * @param formatString
+     *            the format string with which to format the date
+     * @param nullRepresentation
+     *            the textual representation of {@code null} value
+     * @throws IllegalArgumentException
+     *             if {@code formatString} is {@code null}
+     * @see <a
+     *      href="http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax">Format
+     *      String Syntax</a>
+     */
+    public DateRenderer(String formatString, String nullRepresentation) throws IllegalArgumentException {
+        this(formatString, Locale.getDefault(), nullRepresentation);
     }
 
     /**
@@ -95,7 +132,29 @@ public class DateRenderer extends AbstractRenderer<Date> {
      */
     public DateRenderer(String formatString, Locale locale)
             throws IllegalArgumentException {
-        super(Date.class);
+        this(formatString,locale, "");
+    }
+    /**
+     * Creates a new date renderer.
+     * <p>
+     * The renderer is configured to render with the given string format, as
+     * displayed in the given locale.
+     *
+     * @param formatString
+     *            the format string to format the date with
+     * @param locale
+     *            the locale to use
+     * @param nullRepresentation
+     *            the textual representation of {@code null} value
+     * @throws IllegalArgumentException
+     *             if either argument is {@code null}
+     * @see <a
+     *      href="http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax">Format
+     *      String Syntax</a>
+     */
+    public DateRenderer(String formatString, Locale locale, String nullRepresentation)
+            throws IllegalArgumentException {
+        super(Date.class, nullRepresentation);
 
         if (formatString == null) {
             throw new IllegalArgumentException("format string may not be null");
@@ -121,7 +180,20 @@ public class DateRenderer extends AbstractRenderer<Date> {
      *             if {@code dateFormat} is {@code null}
      */
     public DateRenderer(DateFormat dateFormat) throws IllegalArgumentException {
-        super(Date.class);
+        this(dateFormat, "");
+    }
+    /**
+     * Creates a new date renderer.
+     * <p>
+     * The renderer is configured to render with he given date format.
+     *
+     * @param dateFormat
+     *            the date format to use when rendering dates
+     * @throws IllegalArgumentException
+     *             if {@code dateFormat} is {@code null}
+     */
+    public DateRenderer(DateFormat dateFormat, String nullRepresentation) throws IllegalArgumentException {
+        super(Date.class, nullRepresentation);
         if (dateFormat == null) {
             throw new IllegalArgumentException("date format may not be null");
         }
@@ -132,9 +204,16 @@ public class DateRenderer extends AbstractRenderer<Date> {
     }
 
     @Override
+    public String getNullRepresentation() {
+        return super.getNullRepresentation();
+    }
+
+    @Override
     public JsonValue encode(Date value) {
         String dateString;
-        if (dateFormat != null) {
+        if (value == null) {
+            dateString = getNullRepresentation();
+        } else if (dateFormat != null) {
             dateString = dateFormat.format(value);
         } else {
             dateString = String.format(locale, formatString, value);
diff --git a/server/src/com/vaadin/ui/renderers/HtmlRenderer.java b/server/src/com/vaadin/ui/renderers/HtmlRenderer.java
index 34774b3825..df89c60ad2 100644
--- a/server/src/com/vaadin/ui/renderers/HtmlRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/HtmlRenderer.java
@@ -16,18 +16,33 @@
 package com.vaadin.ui.renderers;
 
 import com.vaadin.ui.Grid.AbstractRenderer;
+import elemental.json.JsonValue;
 
 /**
  * A renderer for presenting HTML content.
- * 
- * @since 7.4
+ *
  * @author Vaadin Ltd
+ * @since 7.4
  */
 public class HtmlRenderer extends AbstractRenderer<String> {
     /**
      * Creates a new HTML renderer.
+     *
+     * @param nullRepresentation the html representation of {@code null} value
+     */
+    public HtmlRenderer(String nullRepresentation) {
+        super(String.class, nullRepresentation);
+    }
+
+    /**
+     * Creates a new HTML renderer.
      */
     public HtmlRenderer() {
-        super(String.class);
+        this("");
+    }
+
+    @Override
+    public String getNullRepresentation() {
+        return super.getNullRepresentation();
     }
 }
diff --git a/server/src/com/vaadin/ui/renderers/ImageRenderer.java b/server/src/com/vaadin/ui/renderers/ImageRenderer.java
index 4bb3671033..2fb872583e 100644
--- a/server/src/com/vaadin/ui/renderers/ImageRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/ImageRenderer.java
@@ -39,7 +39,7 @@ public class ImageRenderer extends ClickableRenderer<Resource> {
      * Creates a new image renderer.
      */
     public ImageRenderer() {
-        super(Resource.class);
+        super(Resource.class, null);
     }
 
     /**
@@ -55,7 +55,7 @@ public class ImageRenderer extends ClickableRenderer<Resource> {
 
     @Override
     public JsonValue encode(Resource resource) {
-        if (!(resource instanceof ExternalResource || resource instanceof ThemeResource)) {
+        if (!(resource == null || resource instanceof ExternalResource || resource instanceof ThemeResource)) {
             throw new IllegalArgumentException(
                     "ImageRenderer only supports ExternalResource and ThemeResource ("
                             + resource.getClass().getSimpleName() + "given )");
diff --git a/server/src/com/vaadin/ui/renderers/NumberRenderer.java b/server/src/com/vaadin/ui/renderers/NumberRenderer.java
index 5c30e55b17..1d4d7e0ec9 100644
--- a/server/src/com/vaadin/ui/renderers/NumberRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/NumberRenderer.java
@@ -24,7 +24,7 @@ import elemental.json.JsonValue;
 
 /**
  * A renderer for presenting number values.
- * 
+ *
  * @since 7.4
  * @author Vaadin Ltd
  */
@@ -35,7 +35,7 @@ public class NumberRenderer extends AbstractRenderer<Number> {
 
     /**
      * Creates a new number renderer.
-     * <p>
+     * <p/>
      * The renderer is configured to render with the number's natural string
      * representation in the default locale.
      */
@@ -45,18 +45,35 @@ public class NumberRenderer extends AbstractRenderer<Number> {
 
     /**
      * Creates a new number renderer.
-     * <p>
+     * <p/>
      * The renderer is configured to render the number as defined with the given
      * number format.
-     * 
+     *
      * @param numberFormat
      *            the number format with which to display numbers
      * @throws IllegalArgumentException
      *             if {@code numberFormat} is {@code null}
      */
-    public NumberRenderer(NumberFormat numberFormat)
+    public NumberRenderer(NumberFormat numberFormat) {
+        this(numberFormat, "");
+    }
+
+    /**
+     * Creates a new number renderer.
+     * <p/>
+     * The renderer is configured to render the number as defined with the given
+     * number format.
+     *
+     * @param numberFormat
+     *            the number format with which to display numbers
+     * @param nullRepresentation
+     *            the textual representation of {@code null} value
+     * @throws IllegalArgumentException
+     *            if {@code numberFormat} is {@code null}
+     */
+    public NumberRenderer(NumberFormat numberFormat, String nullRepresentation)
             throws IllegalArgumentException {
-        super(Number.class);
+        super(Number.class, nullRepresentation);
 
         if (numberFormat == null) {
             throw new IllegalArgumentException("Number format may not be null");
@@ -69,10 +86,10 @@ public class NumberRenderer extends AbstractRenderer<Number> {
 
     /**
      * Creates a new number renderer.
-     * <p>
+     * <p/>
      * The renderer is configured to render with the number's natural string
      * representation in the given locale.
-     * 
+     *
      * @param locale
      *            the locale in which to display numbers
      * @throws IllegalArgumentException
@@ -84,12 +101,29 @@ public class NumberRenderer extends AbstractRenderer<Number> {
 
     /**
      * Creates a new number renderer.
-     * <p>
-     * The renderer is configured to render with the given format string in the
-     * default locale.
-     * 
+     * <p/>
+     * The renderer is configured to render with the number's natural string
+     * representation in the given locale.
+     *
      * @param formatString
      *            the format string with which to format the number
+     * @param locale
+     *            the locale in which to display numbers
+     * @throws IllegalArgumentException
+     *             if {@code locale} is {@code null}
+     */
+    public NumberRenderer(String formatString, Locale locale) throws IllegalArgumentException {
+        this(formatString, locale, "");  //This will call #toString() during formatting
+    }
+
+    /**
+     * Creates a new number renderer.
+     * <p/>
+     * The renderer is configured to render with the given format string in the
+     * default locale.
+     *
+     * @param
+     *            formatString the format string with which to format the number
      * @throws IllegalArgumentException
      *             if {@code formatString} is {@code null}
      * @see <a
@@ -97,15 +131,15 @@ public class NumberRenderer extends AbstractRenderer<Number> {
      *      String Syntax</a>
      */
     public NumberRenderer(String formatString) throws IllegalArgumentException {
-        this(formatString, Locale.getDefault());
+        this(formatString, Locale.getDefault(), "");
     }
 
     /**
      * Creates a new number renderer.
-     * <p>
+     * <p/>
      * The renderer is configured to render with the given format string in the
      * given locale.
-     * 
+     *
      * @param formatString
      *            the format string with which to format the number
      * @param locale
@@ -116,8 +150,8 @@ public class NumberRenderer extends AbstractRenderer<Number> {
      *      href="http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax">Format
      *      String Syntax</a>
      */
-    public NumberRenderer(String formatString, Locale locale) {
-        super(Number.class);
+    public NumberRenderer(String formatString, Locale locale, String nullRepresentation) {
+        super(Number.class, nullRepresentation);
 
         if (formatString == null) {
             throw new IllegalArgumentException("Format string may not be null");
@@ -135,7 +169,9 @@ public class NumberRenderer extends AbstractRenderer<Number> {
     @Override
     public JsonValue encode(Number value) {
         String stringValue;
-        if (formatString != null && locale != null) {
+        if (value == null) {
+            stringValue = getNullRepresentation();
+        } else if (formatString != null && locale != null) {
             stringValue = String.format(locale, formatString, value);
         } else if (numberFormat != null) {
             stringValue = numberFormat.format(value);
@@ -160,4 +196,9 @@ public class NumberRenderer extends AbstractRenderer<Number> {
 
         return String.format("%s [%s]", getClass().getSimpleName(), fieldInfo);
     }
+
+    @Override
+    public String getNullRepresentation() {
+        return super.getNullRepresentation();
+    }
 }
diff --git a/server/src/com/vaadin/ui/renderers/ProgressBarRenderer.java b/server/src/com/vaadin/ui/renderers/ProgressBarRenderer.java
index a077cd8012..1566c47222 100644
--- a/server/src/com/vaadin/ui/renderers/ProgressBarRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/ProgressBarRenderer.java
@@ -21,9 +21,9 @@ import elemental.json.JsonValue;
 
 /**
  * A renderer that represents a double values as a graphical progress bar.
- * 
- * @since 7.4
+ *
  * @author Vaadin Ltd
+ * @since 7.4
  */
 public class ProgressBarRenderer extends AbstractRenderer<Double> {
 
@@ -31,13 +31,15 @@ public class ProgressBarRenderer extends AbstractRenderer<Double> {
      * Creates a new text renderer
      */
     public ProgressBarRenderer() {
-        super(Double.class);
+        super(Double.class, null);
     }
 
     @Override
     public JsonValue encode(Double value) {
         if (value != null) {
             value = Math.max(Math.min(value, 1), 0);
+        } else {
+            value = 0d;
         }
         return super.encode(value);
     }
diff --git a/server/src/com/vaadin/ui/renderers/TextRenderer.java b/server/src/com/vaadin/ui/renderers/TextRenderer.java
index 3723a45f70..0045024b2f 100644
--- a/server/src/com/vaadin/ui/renderers/TextRenderer.java
+++ b/server/src/com/vaadin/ui/renderers/TextRenderer.java
@@ -16,6 +16,7 @@
 package com.vaadin.ui.renderers;
 
 import com.vaadin.ui.Grid.AbstractRenderer;
+import elemental.json.JsonValue;
 
 /**
  * A renderer for presenting simple plain-text string values.
@@ -29,6 +30,20 @@ public class TextRenderer extends AbstractRenderer<String> {
      * Creates a new text renderer
      */
     public TextRenderer() {
-        super(String.class);
+        this("");
+    }
+
+    /**
+     * Creates a new text renderer
+     * @param nullRepresentation
+     *            the textual representation of {@code null} value
+     */
+    public TextRenderer(String nullRepresentation) {
+        super(String.class, nullRepresentation);
+    }
+
+    @Override
+    public String getNullRepresentation() {
+        return super.getNullRepresentation();
     }
 }
diff --git a/server/tests/src/com/vaadin/tests/server/renderer/RendererTest.java b/server/tests/src/com/vaadin/tests/server/renderer/RendererTest.java
index 8bcbc6a5a9..8a01464180 100644
--- a/server/tests/src/com/vaadin/tests/server/renderer/RendererTest.java
+++ b/server/tests/src/com/vaadin/tests/server/renderer/RendererTest.java
@@ -15,15 +15,6 @@
  */
 package com.vaadin.tests.server.renderer;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertSame;
-
-import java.util.Locale;
-
-import org.junit.Before;
-import org.junit.Test;
-
 import com.vaadin.data.Item;
 import com.vaadin.data.RpcDataProviderExtension;
 import com.vaadin.data.util.IndexedContainer;
@@ -34,9 +25,21 @@ import com.vaadin.tests.server.component.grid.TestGrid;
 import com.vaadin.tests.util.AlwaysLockedVaadinSession;
 import com.vaadin.ui.Grid;
 import com.vaadin.ui.Grid.Column;
+import com.vaadin.ui.renderers.ButtonRenderer;
+import com.vaadin.ui.renderers.DateRenderer;
+import com.vaadin.ui.renderers.HtmlRenderer;
+import com.vaadin.ui.renderers.NumberRenderer;
 import com.vaadin.ui.renderers.TextRenderer;
-
 import elemental.json.JsonValue;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Date;
+import java.util.Locale;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
 
 public class RendererTest {
 
@@ -64,14 +67,14 @@ public class RendererTest {
 
         @Override
         public TestBean convertToModel(String value,
-                Class<? extends TestBean> targetType, Locale locale)
+                                       Class<? extends TestBean> targetType, Locale locale)
                 throws ConversionException {
             return null;
         }
 
         @Override
         public String convertToPresentation(TestBean value,
-                Class<? extends String> targetType, Locale locale)
+                                            Class<? extends String> targetType, Locale locale)
                 throws ConversionException {
             if (value instanceof ExtendedBean) {
                 return "ExtendedBean(" + value.i + ", "
@@ -94,101 +97,151 @@ public class RendererTest {
 
     private Grid grid;
 
-    private Column foo;
-    private Column bar;
-    private Column baz;
-    private Column bah;
+    private Column intColumn;
+    private Column textColumn;
+    private Column beanColumn;
+    private Column htmlColumn;
+    private Column numberColumn;
+    private Column dateColumn;
+    private Column extendedBeanColumn;
+    private Column buttonColumn;
 
     @Before
+    @SuppressWarnings("unchecked")
     public void setUp() {
         VaadinSession.setCurrent(new AlwaysLockedVaadinSession(null));
 
         IndexedContainer c = new IndexedContainer();
 
-        c.addContainerProperty("foo", Integer.class, 0);
-        c.addContainerProperty("bar", String.class, "");
-        c.addContainerProperty("baz", TestBean.class, null);
-        c.addContainerProperty("bah", ExtendedBean.class, null);
+        c.addContainerProperty("int", Integer.class, 0);
+        c.addContainerProperty("text", String.class, "");
+        c.addContainerProperty("html", String.class, "");
+        c.addContainerProperty("number", Number.class, null);
+        c.addContainerProperty("date", Date.class, null);
+        c.addContainerProperty("bean", TestBean.class, null);
+        c.addContainerProperty("button", String.class, null);
+        c.addContainerProperty("extendedBean", ExtendedBean.class, null);
 
         Object id = c.addItem();
         Item item = c.getItem(id);
-        item.getItemProperty("foo").setValue(123);
-        item.getItemProperty("bar").setValue("321");
-        item.getItemProperty("baz").setValue(new TestBean());
-        item.getItemProperty("bah").setValue(new ExtendedBean());
+        item.getItemProperty("int").setValue(123);
+        item.getItemProperty("text").setValue("321");
+        item.getItemProperty("html").setValue("<b>html</b>");
+        item.getItemProperty("number").setValue(3.14);
+        item.getItemProperty("date").setValue(new Date(123456789));
+        item.getItemProperty("bean").setValue(new TestBean());
+        item.getItemProperty("extendedBean").setValue(new ExtendedBean());
 
         grid = new TestGrid(c);
 
-        foo = grid.getColumn("foo");
-        bar = grid.getColumn("bar");
-        baz = grid.getColumn("baz");
-        bah = grid.getColumn("bah");
+        intColumn = grid.getColumn("int");
+        textColumn = grid.getColumn("text");
+        htmlColumn = grid.getColumn("html");
+        numberColumn = grid.getColumn("number");
+        dateColumn = grid.getColumn("date");
+        beanColumn = grid.getColumn("bean");
+        extendedBeanColumn = grid.getColumn("extendedBean");
+        buttonColumn = grid.getColumn("button");
+
     }
 
     @Test
     public void testDefaultRendererAndConverter() throws Exception {
-        assertSame(TextRenderer.class, foo.getRenderer().getClass());
-        assertSame(StringToIntegerConverter.class, foo.getConverter()
+        assertSame(TextRenderer.class, intColumn.getRenderer().getClass());
+        assertSame(StringToIntegerConverter.class, intColumn.getConverter()
                 .getClass());
 
-        assertSame(TextRenderer.class, bar.getRenderer().getClass());
+        assertSame(TextRenderer.class, textColumn.getRenderer().getClass());
         // String->String; converter not needed
-        assertNull(bar.getConverter());
+        assertNull(textColumn.getConverter());
 
-        assertSame(TextRenderer.class, baz.getRenderer().getClass());
+        assertSame(TextRenderer.class, beanColumn.getRenderer().getClass());
         // MyBean->String; converter not found
-        assertNull(baz.getConverter());
+        assertNull(beanColumn.getConverter());
     }
 
     @Test
     public void testFindCompatibleConverter() throws Exception {
-        foo.setRenderer(renderer());
-        assertSame(StringToIntegerConverter.class, foo.getConverter()
+        intColumn.setRenderer(renderer());
+        assertSame(StringToIntegerConverter.class, intColumn.getConverter()
                 .getClass());
 
-        bar.setRenderer(renderer());
-        assertNull(bar.getConverter());
+        textColumn.setRenderer(renderer());
+        assertNull(textColumn.getConverter());
     }
 
     @Test(expected = IllegalArgumentException.class)
     public void testCannotFindConverter() {
-        baz.setRenderer(renderer());
+        beanColumn.setRenderer(renderer());
     }
 
     @Test
     public void testExplicitConverter() throws Exception {
-        baz.setRenderer(renderer(), converter());
-        bah.setRenderer(renderer(), converter());
+        beanColumn.setRenderer(renderer(), converter());
+        extendedBeanColumn.setRenderer(renderer(), converter());
     }
 
     @Test
     public void testEncoding() throws Exception {
-        assertEquals("42", render(foo, 42).asString());
-        foo.setRenderer(renderer());
-        assertEquals("renderer(42)", render(foo, 42).asString());
+        assertEquals("42", render(intColumn, 42).asString());
+        intColumn.setRenderer(renderer());
+        assertEquals("renderer(42)", render(intColumn, 42).asString());
 
-        assertEquals("2.72", render(bar, "2.72").asString());
-        bar.setRenderer(new TestRenderer());
-        assertEquals("renderer(2.72)", render(bar, "2.72").asString());
+        assertEquals("2.72", render(textColumn, "2.72").asString());
+        textColumn.setRenderer(new TestRenderer());
+        assertEquals("renderer(2.72)", render(textColumn, "2.72").asString());
     }
 
     @Test
     public void testEncodingWithoutConverter() throws Exception {
-        assertEquals("TestBean [42]", render(baz, new TestBean()).asString());
+        assertEquals("TestBean [42]", render(beanColumn, new TestBean())
+                .asString());
     }
 
     @Test
     public void testBeanEncoding() throws Exception {
-        baz.setRenderer(renderer(), converter());
-        bah.setRenderer(renderer(), converter());
+        beanColumn.setRenderer(renderer(), converter());
+        extendedBeanColumn.setRenderer(renderer(), converter());
 
-        assertEquals("renderer(TestBean(42))", render(baz, new TestBean())
-                .asString());
+        assertEquals("renderer(TestBean(42))",
+                render(beanColumn, new TestBean()).asString());
         assertEquals("renderer(ExtendedBean(42, 3.14))",
-                render(baz, new ExtendedBean()).asString());
+                render(beanColumn, new ExtendedBean()).asString());
 
         assertEquals("renderer(ExtendedBean(42, 3.14))",
-                render(bah, new ExtendedBean()).asString());
+                render(extendedBeanColumn, new ExtendedBean()).asString());
+    }
+
+    @Test
+    public void testNullEncoding() {
+
+        textColumn.setRenderer(new TextRenderer());
+        htmlColumn.setRenderer(new HtmlRenderer());
+        numberColumn.setRenderer(new NumberRenderer());
+        dateColumn.setRenderer(new DateRenderer());
+        buttonColumn.setRenderer(new ButtonRenderer());
+
+        assertEquals("", textColumn.getRenderer().encode(null).asString());
+        assertEquals("", htmlColumn.getRenderer().encode(null).asString());
+        assertEquals("", numberColumn.getRenderer().encode(null).asString());
+        assertEquals("", dateColumn.getRenderer().encode(null).asString());
+        assertEquals("", buttonColumn.getRenderer().encode(null).asString());
+    }
+    @Test
+
+    public void testNullEncodingWithDefault() {
+
+        textColumn.setRenderer(new TextRenderer("default value"));
+        htmlColumn.setRenderer(new HtmlRenderer("default value"));
+        numberColumn.setRenderer(new NumberRenderer("%s", Locale.getDefault(), "default value"));
+        dateColumn.setRenderer(new DateRenderer("%s", "default value"));
+        buttonColumn.setRenderer(new ButtonRenderer("default value"));
+
+        assertEquals("default value", textColumn.getRenderer().encode(null).asString());
+        assertEquals("default value", htmlColumn.getRenderer().encode(null).asString());
+        assertEquals("default value", numberColumn.getRenderer().encode(null).asString());
+        assertEquals("default value", dateColumn.getRenderer().encode(null).asString());
+        assertEquals("default value", buttonColumn.getRenderer().encode(null).asString());
     }
 
     private TestConverter converter() {