feat: Add method to write only the changed properties to the bean (#1…

…8636)

* feat: Add method to write only the changed properties to the bean

* Add unit tests for new methods

* Update test bean

* Fixes according to review

- Sanity check bindings to write in writeBean
- Return immutable Set in getBindings

* Update tests

* Formatting

---------

Co-authored-by: Teppo Kurki <teppo.kurki@vaadin.com>

flow-data/src/main/java/com/vaadin/flow/data/binder/Binder.java

@@ -2325,6 +2325,7 @@ public void refreshFields() {
      * thrown.
      *
      * @see #writeBeanIfValid(Object)
+     * @see #writeBean(Object, Collection)
      * @see #readBean(Object)
      * @see #setBean(Object)
      *
@@ -2335,13 +2336,94 @@ public void refreshFields() {
      *             if some of the bound field values fail to validate
      */
     public void writeBean(BEAN bean) throws ValidationException {
-        BinderValidationStatus<BEAN> status = doWriteIfValid(bean, bindings);
+        writeBean(bean, bindings);
+    }
+
+    /**
+     * Writes changes from the given bindings to the given bean if all
+     * validators (binding and bean level) pass.
+     * <p>
+     * If any field binding validator fails, no values are written and a
+     * {@code ValidationException} is thrown.
+     * <p>
+     * If all field level validators pass, the given bean is updated and bean
+     * level validators are run on the updated bean. If any bean level validator
+     * fails, the bean updates are reverted and a {@code ValidationException} is
+     * thrown.
+     *
+     * @see #writeBeanIfValid(Object)
+     * @see #writeBean(Object)
+     * @see #readBean(Object)
+     * @see #setBean(Object)
+     * @see #writeChangedBindingsToBean(Object)
+     *
+     * @param bean
+     *            the object to which to write the field values, not
+     *            {@code null}
+     * @param bindingsToWrite
+     *            Collection of bindings to use in writing the bean
+     * @throws ValidationException
+     *             if some of the bound field values fail to validate
+     * @throws IllegalArgumentException
+     *             if bindingsToWrite contains bindings not belonging to this
+     *             Binder
+     */
+    public void writeBean(BEAN bean,
+            Collection<Binding<BEAN, ?>> bindingsToWrite)
+            throws ValidationException {
+        if (!bindings.containsAll(bindingsToWrite)) {
+            throw new IllegalArgumentException(
+                    "Can't write bean using binding that is not bound to this Binder.");
+        }
+        BinderValidationStatus<BEAN> status = doWriteIfValid(bean,
+                bindingsToWrite);
         if (status.hasErrors()) {
             throw new ValidationException(status.getFieldValidationErrors(),
                     status.getBeanValidationErrors());
         }
     }
 
+    /**
+     * Writes changes from the changed bindings to the given bean if all
+     * validators (binding and bean level) pass. If the bean is the same
+     * instance where Binder read the bean, this method updates the bean with
+     * the changes.
+     * <p>
+     * If any field binding validator fails, no values are written and a
+     * {@code ValidationException} is thrown.
+     * <p>
+     * If all field level validators pass, the given bean is updated and bean
+     * level validators are run on the updated bean. If any bean level validator
+     * fails, the bean updates are reverted and a {@code ValidationException} is
+     * thrown.
+     *
+     * @see #writeBeanIfValid(Object)
+     * @see #writeBean(Object)
+     * @see #readBean(Object)
+     * @see #setBean(Object)
+     *
+     * @param bean
+     *            the object to which to write the field values, not
+     *            {@code null}
+     * @throws ValidationException
+     *             if some of the bound field values fail to validate
+     */
+    public void writeChangedBindingsToBean(BEAN bean)
+            throws ValidationException {
+        writeBean(bean, getChangedBindings());
+    }
+
+    /**
+     * Get the immutable Set of changed bindings.
+     *
+     * @see #hasChanges()
+     *
+     * @return Immutable set of bindings.
+     */
+    public Set<Binding<BEAN, ?>> getChangedBindings() {
+        return Collections.unmodifiableSet(changedBindings);
+    }
+
     /**
      * Writes successfully converted and validated changes from the bound fields
      * to the bean even if there are other fields with non-validated changes.

flow-data/src/test/java/com/vaadin/flow/data/binder/BinderTest.java

@@ -25,6 +25,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
@@ -443,6 +444,86 @@ public void save_bound_beanIsUpdated() throws ValidationException {
         Assert.assertEquals(fieldValue, person.getFirstName());
     }
 
+    @Test
+    public void write_binding_bound_propertyIsUpdated()
+            throws ValidationException {
+        Binder<Person> binder = new Binder<>();
+        Binding<Person, String> binding = binder.bind(nameField,
+                Person::getFirstName, Person::setFirstName);
+        binder.forField(ageField)
+                .withConverter(new StringToIntegerConverter(""))
+                .bind(Person::getAge, Person::setAge);
+
+        Person person = new Person();
+
+        String nameValue = "bar";
+        nameField.setValue(nameValue);
+        String ageValue = "10";
+        ageField.setValue(ageValue);
+
+        person.setFirstName("foo");
+        person.setAge(20);
+
+        binder.writeBean(person, Set.of(binding));
+
+        Assert.assertEquals(1, person.getAgeSetterCallcount());
+        Assert.assertEquals(nameValue, person.getFirstName());
+        Assert.assertNotEquals((int) Integer.valueOf(ageValue),
+                person.getAge());
+    }
+
+    @Test
+    public void write_changedBindings_bound_propertyIsUpdated()
+            throws ValidationException {
+        Binder<Person> binder = new Binder<>();
+        binder.bind(nameField, Person::getFirstName, Person::setFirstName);
+        binder.forField(ageField)
+                .withConverter(new StringToIntegerConverter(""))
+                .bind(Person::getAge, Person::setAge);
+
+        Person person = new Person();
+        Person updatedPerson = new Person();
+
+        String nameValue = "bar";
+        nameField.setValue(nameValue);
+
+        person.setFirstName("foo");
+        person.setAge(20);
+
+        Assert.assertEquals(1, binder.getChangedBindings().size());
+        binder.writeBean(updatedPerson, binder.getChangedBindings());
+
+        Assert.assertEquals(0, updatedPerson.getAgeSetterCallcount());
+        Assert.assertEquals(nameValue, updatedPerson.getFirstName());
+        Assert.assertEquals(0, updatedPerson.getAge());
+    }
+
+    @Test
+    public void update_bound_propertyIsUpdated() throws ValidationException {
+        Binder<Person> binder = new Binder<>();
+        binder.bind(nameField, Person::getFirstName, Person::setFirstName);
+        binder.forField(ageField)
+                .withConverter(new StringToIntegerConverter(""))
+                .bind(Person::getAge, Person::setAge);
+
+        Person person = new Person();
+        Person updatedPerson = new Person();
+
+        String nameValue = "bar";
+        nameField.setValue(nameValue);
+
+        person.setFirstName("foo");
+        person.setAge(20);
+
+        Assert.assertEquals(1, binder.getChangedBindings().size());
+
+        binder.writeChangedBindingsToBean(updatedPerson);
+
+        Assert.assertEquals(0, updatedPerson.getAgeSetterCallcount());
+        Assert.assertEquals(nameValue, updatedPerson.getFirstName());
+        Assert.assertEquals(0, updatedPerson.getAge());
+    }
+
     @Test
     public void save_bound_beanAsDraft() {
         do_test_save_bound_beanAsDraft(false);

flow-data/src/test/java/com/vaadin/flow/tests/data/bean/Person.java

@@ -19,6 +19,8 @@ public class Person implements Serializable {
 
     private BigDecimal rent;
 
+    private int ageCallcount = 0;
+
     public Person() {
 
     }
@@ -64,6 +66,7 @@ public int getAge() {
     }
 
     public void setAge(int age) {
+        ageCallcount++;
         this.age = age;
     }
 
@@ -141,4 +144,8 @@ public static Person createTestPerson2() {
                 new Address("Red street", 12, "Amsterdam",
                         Country.NETHERLANDS));
     }
+
+    public int getAgeSetterCallcount() {
+        return ageCallcount;
+    }
 }