Enable changing the backing bean for BeanItem (#4302) (#77)

When storing a bean to the database, you typically get a new and updated
bean instance back. By allowing to change the bean instance, we make it
possible to just update the single BeanItem instance which can be used
in many places.

server/src/main/java/com/vaadin/data/util/BeanItem.java

@@ -26,6 +26,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import com.vaadin.data.Property;
+
 /**
  * A wrapper class for adding the Item interface to any Java Bean.
  *
@@ -38,7 +40,7 @@ public class BeanItem<BT> extends PropertysetItem {
     /**
      * The bean which this Item is based on.
      */
-    private final BT bean;
+    private BT bean;
 
     /**
      * <p>
@@ -261,4 +263,46 @@ public class BeanItem<BT> extends PropertysetItem {
         return bean;
     }
 
+    /**
+     * Changes the Java Bean this item is based on.
+     * <p>
+     * This will cause any existing properties to be re-mapped to the new bean.
+     * Any added custom properties which are not of type {@link MethodProperty}
+     * or {@link NestedMethodProperty} will not be updated to reflect the change
+     * of bean.
+     * <p>
+     * Changing the bean will fire value change events for all properties of
+     * type {@link MethodProperty} or {@link NestedMethodProperty}.
+     * 
+     * @param bean
+     *            The new bean to use for this item, not <code>null</code>
+     */
+    public void setBean(BT bean) {
+        if (bean == null) {
+            throw new IllegalArgumentException("Bean cannot be null");
+        }
+
+        if (getBean().getClass() != bean.getClass()) {
+            throw new IllegalArgumentException(
+                    "The new bean class " + bean.getClass().getName()
+                            + " does not match the old bean class "
+                            + getBean().getClass());
+        }
+
+        // Remap properties
+        for (Object propertyId : getItemPropertyIds()) {
+            Property p = getItemProperty(propertyId);
+            if (p instanceof MethodProperty) {
+                MethodProperty mp = (MethodProperty) p;
+                assert (mp.getInstance() == getBean());
+                mp.setInstance(bean);
+            } else if (p instanceof NestedMethodProperty) {
+                NestedMethodProperty nmp = (NestedMethodProperty) p;
+                assert (nmp.getInstance() == getBean());
+                nmp.setInstance(bean);
+            }
+        }
+
+        this.bean = bean;
+    }
 }

server/src/main/java/com/vaadin/data/util/MethodProperty.java

@@ -767,6 +767,37 @@ public class MethodProperty<T> extends AbstractProperty<T> {
         super.fireValueChange();
     }
 
+    /**
+     * The instance used by this property
+     *
+     * @return the instance used for fetching the property value
+     */
+    public Object getInstance() {
+        return instance;
+    }
+
+    /**
+     * Sets the instance used by this property.
+     * <p>
+     * The new instance must be of the same type as the old instance
+     * <p>
+     * To be consistent with {@link #setValue(Object)}, this method will fire a
+     * value change event even if the value stays the same
+     *
+     * @param instance
+     *            the instance to use
+     */
+    public void setInstance(Object instance) {
+        if (this.instance.getClass() != instance.getClass()) {
+            throw new IllegalArgumentException("The new instance is of type "
+                    + instance.getClass().getName()
+                    + " which does not match the old instance type "
+                    + this.instance.getClass().getName());
+        }
+        this.instance = instance;
+        fireValueChange();
+    }
+
     private static final Logger getLogger() {
         return Logger.getLogger(MethodProperty.class.getName());
     }

server/src/main/java/com/vaadin/data/util/NestedMethodProperty.java

@@ -192,9 +192,10 @@ public class NestedMethodProperty<T> extends AbstractProperty<T> {
 
     /**
      * Gets the value stored in the Property. The value is resolved by calling
-     * the specified getter method with the argument specified at instantiation.
+     * the specified getter methods on the current instance:
      *
      * @return the value of the Property
+     * @see #getInstance()
      */
     @Override
     public T getValue() {
@@ -266,4 +267,35 @@ public class NestedMethodProperty<T> extends AbstractProperty<T> {
         return Collections.unmodifiableList(getMethods);
     }
 
+    /**
+     * The instance used by this property
+     * 
+     * @return the instance used for fetching the property value
+     */
+    public Object getInstance() {
+        return instance;
+    }
+
+    /**
+     * Sets the instance used by this property.
+     * <p>
+     * The new instance must be of the same type as the old instance
+     * <p>
+     * To be consistent with {@link #setValue(Object)}, this method will fire a
+     * value change event even if the value stays the same
+     * 
+     * @param instance
+     *            the instance to use
+     */
+    public void setInstance(Object instance) {
+        if (this.instance.getClass() != instance.getClass()) {
+            throw new IllegalArgumentException("The new instance is of type "
+                    + instance.getClass().getName()
+                    + " which does not match the old instance type "
+                    + this.instance.getClass().getName());
+        }
+        this.instance = instance;
+        fireValueChange();
+    }
+
 }

server/src/test/java/com/vaadin/data/util/BeanItemTest.java

@@ -386,4 +386,41 @@ public class BeanItemTest {
         // Should not be exception
         property.setValue(null);
     }
+
+    @Test
+    public void testChangeBean() {
+        BeanItem<MyClass> beanItem = new BeanItem<BeanItemTest.MyClass>(
+                new MyClass("Foo"));
+        beanItem.setBean(new MyClass("Bar"));
+        Assert.assertEquals("Bar", beanItem.getItemProperty("name").getValue());
+    }
+
+    @Test
+    public void testChangeBeanNestedProperty() {
+        BeanItem<MyClass> beanItem = new BeanItem<BeanItemTest.MyClass>(
+                new MyClass("Foo"));
+        beanItem.setBean(new MyClass("Bar"));
+        Assert.assertEquals("Bar", beanItem.getItemProperty("name").getValue());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testChangeBeanToIncompatibleOne() {
+        BeanItem<Object> beanItem = new BeanItem<Object>(new MyClass("Foo"));
+        beanItem.setBean(new Generic<String>());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testChangeBeanToSubclass() {
+        BeanItem<MyClass> beanItem = new BeanItem<BeanItemTest.MyClass>(
+                new MyClass("Foo"));
+        beanItem.setBean(new MyClass("Bar"));
+        beanItem.setBean(new MyClass2("foo"));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testChangeBeanToNull() {
+        BeanItem<Object> beanItem = new BeanItem<Object>(new MyClass("Foo"));
+        beanItem.setBean(null);
+    }
+
 }

server/src/test/java/com/vaadin/data/util/MethodPropertyTest.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2000-2014 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.util;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.vaadin.data.util.NestedMethodPropertyTest.Address;
+
+public class MethodPropertyTest {
+
+    private Address testObject;
+
+    @Before
+    public void setup() {
+        testObject = new NestedMethodPropertyTest.Address("some street", 123);
+    }
+
+    @Test
+    public void getValue() {
+        MethodProperty<String> mp = new MethodProperty<String>(testObject,
+                "street");
+        Assert.assertEquals("some street", mp.getValue());
+    }
+
+    @Test
+    public void getValueAfterBeanUpdate() {
+        MethodProperty<String> mp = new MethodProperty<String>(testObject,
+                "street");
+        testObject.setStreet("Foo street");
+        Assert.assertEquals("Foo street", mp.getValue());
+    }
+
+    @Test
+    public void setValue() {
+        MethodProperty<String> mp = new MethodProperty<String>(testObject,
+                "street");
+        mp.setValue("Foo street");
+        Assert.assertEquals("Foo street", testObject.getStreet());
+    }
+
+    @Test
+    public void changeInstance() {
+        MethodProperty<String> mp = new MethodProperty<String>(testObject,
+                "street");
+        Address newStreet = new Address("new street", 999);
+        mp.setInstance(newStreet);
+        Assert.assertEquals("new street", mp.getValue());
+        Assert.assertEquals("some street", testObject.getStreet());
+
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void changeInstanceToIncompatible() {
+        MethodProperty<String> mp = new MethodProperty<String>(testObject,
+                "street");
+        mp.setInstance("foobar");
+
+    }
+
+}

server/src/test/java/com/vaadin/data/util/NestedMethodPropertyTest.java

@@ -348,4 +348,27 @@ public class NestedMethodPropertyTest {
         Assert.assertTrue(booleanProperty.isReadOnly());
     }
 
+    @Test
+    public void testChangeInstance() {
+        NestedMethodProperty<String> streetProperty = new NestedMethodProperty<String>(
+                vaadin, "manager.address.street");
+
+        Address somewhere = new Address("The street", 1234);
+        Person someone = new Person("Someone", somewhere);
+        Team someteam = new Team("The team", someone);
+        streetProperty.setInstance(someteam);
+
+        Assert.assertEquals("The street", streetProperty.getValue());
+        Assert.assertEquals("Ruukinkatu 2-4", vaadin.getManager().getAddress()
+                .getStreet());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testChangeInstanceToIncompatible() {
+        NestedMethodProperty<String> streetProperty = new NestedMethodProperty<String>(
+                vaadin, "manager.address.street");
+
+        streetProperty.setInstance("bar");
+    }
+
 }