Implement ReadOnlyHasValue helper (#10643)

documentation/datamodel/datamodel-forms.asciidoc

@@ -91,6 +91,18 @@ binder.bind(nameField,
     }
   });
 ----
+== Binding non-modifiable Data
+
+Non-modifiable data can be also bound to any component or component property with [classname]#ReadOnlyHasValue# helper class.
+For example, `Panel` caption can display a person full name:
+
+[source, java]
+----
+Panel infoPanel = new Panel();
+ReadOnlyHasValue<Person> panelTitle = new ReadOnlyHasValue<>(
+        person -> infoPanel.setCaption(person.getLastName() + ", " + person.getFirstName()));
+binder.forField(panelTitle).bind(person -> person, null);
+----
 
 == Validating and Converting User Input
 

server/src/main/java/com/vaadin/data/ReadOnlyHasValue.java

@@ -0,0 +1,119 @@
+/*
+ * 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.data;
+
+import com.vaadin.server.SerializableConsumer;
+import com.vaadin.shared.Registration;
+import com.vaadin.ui.Label;
+
+import java.io.Serializable;
+import java.util.LinkedHashSet;
+import java.util.Objects;
+
+/**
+ * Generic {@link HasValue} to use any type of component with Vaadin data binding.
+ * <p>
+ * Example:
+ * <pre>
+ * Label label = new Label();
+ * ReadOnlyHasValue&lt;String&gt; hasValue = new ReadOnlyHasValue&lt;&gt;(label::setCaption);
+ * binder.forField(hasValue).bind(SomeBean::getName);
+ * </pre>
+ *
+ * @param <V> the value type
+ * @since
+ */
+public class ReadOnlyHasValue<V> implements HasValue<V>, Serializable {
+    private V value;
+    private final SerializableConsumer<V> valueProcessor;
+    private final V emptyValue;
+    private LinkedHashSet<ValueChangeListener<V>> listenerList;
+
+    /**
+     * Creates new {@code ReadOnlyHasValue}
+     *
+     * @param valueProcessor the value valueProcessor, e.g. {@link Label#setValue}
+     * @param emptyValue the value to be used as empty, {@code null} by default
+     */
+    public ReadOnlyHasValue(SerializableConsumer<V> valueProcessor, V emptyValue) {
+        this.valueProcessor = valueProcessor;
+        this.emptyValue = emptyValue;
+    }
+
+    /**
+     * Creates new {@code ReadOnlyHasValue} with {@code null} as an empty value.
+     *
+     * @param valueProcessor the value valueProcessor, e.g. {@link Label#setValue}
+     */
+    public ReadOnlyHasValue(SerializableConsumer<V> valueProcessor) {
+        this(valueProcessor,null);
+    }
+
+    @Override
+    public void setValue(V value) {
+        V oldValue = this.value;
+        this.value = value;
+        valueProcessor.accept(value);
+        if (listenerList != null && ! Objects.equals(oldValue, value)) {
+            for (ValueChangeListener<V> valueChangeListener : listenerList) {
+                valueChangeListener.valueChange(
+                        new ValueChangeEvent<>(null, this, oldValue, false));
+            }
+        }
+    }
+
+    @Override
+    public V getValue() {
+        return value;
+    }
+
+    @Override
+    public Registration addValueChangeListener(
+            ValueChangeListener<V> listener) {
+        Objects.requireNonNull(listener, "Listener must not be null.");
+        if (listenerList == null) {
+            listenerList = new LinkedHashSet<>();
+        }
+        listenerList.add(listener);
+
+        return () -> listenerList.remove(listener);
+    }
+
+    @Override
+    public boolean isRequiredIndicatorVisible() {
+        return false;
+    }
+
+    @Override
+    public void setRequiredIndicatorVisible(boolean requiredIndicatorVisible) {
+        if (requiredIndicatorVisible) throw new IllegalArgumentException("Not Writable");
+    }
+
+    @Override
+    public void setReadOnly(boolean readOnly) {
+        if (!readOnly) throw new IllegalArgumentException("Not Writable");
+    }
+
+    @Override
+    public boolean isReadOnly() {
+        return true;
+    }
+
+    @Override
+    public V getEmptyValue() {
+        return emptyValue;
+    }
+}

server/src/test/java/com/vaadin/data/ReadOnlyHasValueTest.java

@@ -0,0 +1,116 @@
+package com.vaadin.data;
+
+import com.vaadin.shared.Registration;
+import com.vaadin.ui.Label;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Objects;
+
+import static org.junit.Assert.*;
+
+public class ReadOnlyHasValueTest {
+    private static final String SAY_SOMETHING = "Say something";
+    private static final String SAY_SOMETHING_ELSE = "Say something else";
+    private static final String NO_VALUE = "-no-value-";
+    private Label label;
+    private ReadOnlyHasValue<String> hasValue;
+
+    @Before
+    public void setup() {
+        label = new Label();
+        hasValue = new ReadOnlyHasValue<>(label::setCaption);
+    }
+
+    @Test
+    public void testBase() {
+        hasValue.setReadOnly(true);
+        hasValue.setRequiredIndicatorVisible(false);
+        Registration registration = hasValue.addValueChangeListener(e -> {
+        });
+        registration.remove();
+        hasValue.setValue(SAY_SOMETHING);
+        assertEquals(SAY_SOMETHING, hasValue.getValue());
+        assertEquals(SAY_SOMETHING, label.getCaption());
+        hasValue.setValue(SAY_SOMETHING_ELSE);
+        assertEquals(SAY_SOMETHING_ELSE, hasValue.getValue());
+        assertEquals(SAY_SOMETHING_ELSE, label.getCaption());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testRO() {
+        hasValue.setReadOnly(false);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testIndicator() {
+        hasValue.setRequiredIndicatorVisible(true);
+    }
+
+    @Test
+    public void testBind() {
+        Binder<Bean> beanBinder = new Binder<>(Bean.class);
+        Label label = new Label();
+        ReadOnlyHasValue<Long> intHasValue = new ReadOnlyHasValue<>(
+                i -> label.setValue(Objects.toString(i, "")));
+
+        beanBinder.forField(intHasValue).bind("v");
+
+        beanBinder.readBean(new Bean(42));
+        assertEquals("42", label.getValue());
+        assertEquals(42L, intHasValue.getValue().longValue());
+
+        Registration registration = intHasValue.addValueChangeListener(e -> {
+            assertEquals(42L, e.getOldValue().longValue());
+            assertSame(intHasValue, e.getSource());
+            assertSame(null, e.getComponent());
+            assertSame(null, e.getComponent());
+            assertFalse(e.isUserOriginated());
+        });
+        beanBinder.readBean(new Bean(1984));
+        assertEquals("1984", label.getValue());
+        assertEquals(1984L, intHasValue.getValue().longValue());
+
+        registration.remove();
+
+        beanBinder.readBean(null);
+        assertEquals("", label.getValue());
+        assertEquals(null, intHasValue.getValue());
+
+    }
+
+    @Test
+    public void testEmptyValue() {
+        Binder<Bean> beanBinder = new Binder<>(Bean.class);
+        Label label = new Label();
+        ReadOnlyHasValue<String> strHasValue =
+                new ReadOnlyHasValue<>(label::setValue, NO_VALUE);
+
+        beanBinder.forField(strHasValue)
+                .withConverter(Long::parseLong,(Long i)->"" + i)
+                .bind("v");
+
+        beanBinder.readBean(new Bean(42));
+        assertEquals("42", label.getValue());
+
+        beanBinder.readBean(null);
+        assertEquals(NO_VALUE, label.getValue());
+        assertTrue(strHasValue.isEmpty());
+    }
+
+    public static class Bean {
+        public Bean(long v) {
+            this.v = v;
+        }
+
+        private long v;
+
+        public long getV() {
+            return v;
+        }
+
+        public void setV(long v) {
+            this.v = v;
+        }
+    }
+}