1 files changed, 139 insertions, 0 deletions
diff --git a/server/src/main/java/com/vaadin/ui/renderers/AbstractRenderer.java b/server/src/main/java/com/vaadin/ui/renderers/AbstractRenderer.java
new file mode 100644
index 0000000000..4dcf911515
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+++ b/server/src/main/java/com/vaadin/ui/renderers/AbstractRenderer.java
@@ -0,0 +1,139 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.ui.renderers;
+
+import java.util.Objects;
+
+import com.vaadin.server.AbstractClientConnector;
+import com.vaadin.server.AbstractExtension;
+import com.vaadin.server.JsonCodec;
+import com.vaadin.ui.Grid.Column;
+
+import elemental.json.JsonValue;
+
+/**
+ * An abstract base class for server-side
+ * {@link com.vaadin.ui.renderers.Renderer Grid renderers}. This class currently
+ * extends the AbstractExtension superclass, but this fact should be regarded as
+ * an implementation detail and subject to change in a future major or minor
+ * Vaadin version.
+ *
+ * @param <T>
+ *            the type this renderer knows how to present
+ */
+public abstract class AbstractRenderer<T> extends AbstractExtension
+        implements Renderer<T> {
+    private final Class<T> presentationType;
+
+    private final String nullRepresentation;
+
+    /**
+     * Creates a new renderer with the given presentation type and null
+     * representation.
+     *
+     * @param presentationType
+     *            the data type that this renderer displays, not
+     *            <code>null</code>
+     * @param nullRepresentation
+     *            a string that will be sent to the client instead of a regular
+     *            value in case the actual cell value is <code>null</code>. May
+     *            be <code>null</code>.
+     */
+    protected AbstractRenderer(Class<T> presentationType,
+            String nullRepresentation) {
+        Objects.requireNonNull(presentationType,
+                "Presentation type cannot be null");
+        this.presentationType = presentationType;
+        this.nullRepresentation = nullRepresentation;
+    }
+
+    /**
+     * Creates a new renderer with the given presentation type. No null
+     * representation will be used.
+     *
+     * @param presentationType
+     *            the data type that this renderer displays, not
+     *            <code>null</code>
+     */
+    protected AbstractRenderer(Class<T> presentationType) {
+        this(presentationType, null);
+    }
+
+    /**
+     * This method is inherited from AbstractExtension but should never be
+     * called directly with an AbstractRenderer.
+     */
+    @Deprecated
+    @Override
+    @SuppressWarnings("rawtypes")
+    protected Class<Column> getSupportedParentType() {
+        return Column.class;
+    }
+
+    /**
+     * This method is inherited from AbstractExtension but should never be
+     * called directly with an AbstractRenderer.
+     */
+    @Deprecated
+    @Override
+    protected void extend(AbstractClientConnector target) {
+        super.extend(target);
+    }
+
+    @Override
+    public Class<T> getPresentationType() {
+        return presentationType;
+    }
+
+    @Override
+    public JsonValue encode(T value) {
+        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;
+    }
+
+    /**
+     * Encodes the given value to JSON.
+     * <p>
+     * This is a helper method that can be invoked by an {@link #encode(Object)
+     * encode(T)} override if serializing a value of type other than
+     * {@link #getPresentationType() the presentation type} is desired. For
+     * instance, a {@code Renderer<Date>} could first turn a date value into a
+     * formatted string and return {@code encode(dateString, String.class)}.
+     *
+     * @param value
+     *            the value to be encoded
+     * @param type
+     *            the type of the value
+     * @return a JSON representation of the given value
+     */
+    protected <U> JsonValue encode(U value, Class<U> type) {
+        return JsonCodec
+                .encode(value, null, type, getUI().getConnectorTracker())
+                .getEncodedValue();
+    }
+}
+\ No newline at end of file