Add API to read Binding value from bean (#10316)

2 files changed, 43 insertions, 3 deletions

diff --git a/server/src/main/java/com/vaadin/data/Binder.java b/server/src/main/java/com/vaadin/data/Binder.java
index 8ca90ebaf8..03a6c1eb52 100644
--- a/server/src/main/java/com/vaadin/data/Binder.java
+++ b/server/src/main/java/com/vaadin/data/Binder.java
@@ -165,6 +165,16 @@ public class Binder<BEAN> implements Serializable {
          * @since 8.2
          */
         public void unbind();
+
+        /**
+         * Reads the value from given item and stores it to the bound field.
+         *
+         * @param bean
+         *            the bean to read from
+         *
+         * @since 8.2
+         */
+        public void read(BEAN bean);
     }
 
     /**
@@ -516,9 +526,11 @@ public class Binder<BEAN> implements Serializable {
                 TARGET nullRepresentation) {
             return withConverter(
                     fieldValue -> Objects.equals(fieldValue, nullRepresentation)
-                            ? null : fieldValue,
+                            ? null
+                            : fieldValue,
                     modelValue -> Objects.isNull(modelValue)
-                            ? nullRepresentation : modelValue);
+                            ? nullRepresentation
+                            : modelValue);
         }
 
         /**
@@ -1099,6 +1111,12 @@ public class Binder<BEAN> implements Serializable {
         public BindingValidationStatusHandler getValidationStatusHandler() {
             return statusHandler;
         }
+
+        @Override
+        public void read(BEAN bean) {
+            field.setValue(converterValidatorChain.convertToPresentation(
+                    getter.apply(bean), createValueContext()));
+        }
     }
 
     /**
@@ -2299,7 +2317,8 @@ public class Binder<BEAN> implements Serializable {
         Converter<FIELDVALUE, FIELDVALUE> nullRepresentationConverter = Converter
                 .from(fieldValue -> fieldValue,
                         modelValue -> Objects.isNull(modelValue)
-                                ? field.getEmptyValue() : modelValue,
+                                ? field.getEmptyValue()
+                                : modelValue,
                         exception -> exception.getMessage());
         ConverterDelegate<FIELDVALUE> converter = new ConverterDelegate<>(
                 nullRepresentationConverter);
diff --git a/server/src/test/java/com/vaadin/data/BinderTest.java b/server/src/test/java/com/vaadin/data/BinderTest.java
index 7b45ee95e0..b3bce11e87 100644
--- a/server/src/test/java/com/vaadin/data/BinderTest.java
+++ b/server/src/test/java/com/vaadin/data/BinderTest.java
@@ -990,4 +990,25 @@ public class BinderTest extends BinderTestBase<Binder<Person>, Person> {
         assertNull("Age field should still be ok.",
                 ageField.getComponentError());
     }
+
+    @Test
+    public void refreshValueFromBean() {
+        Binding<Person, String> binding = binder.bind(nameField,
+                Person::getFirstName, Person::setFirstName);
+
+        binder.readBean(item);
+
+        assertEquals("Name should be read from the item", item.getFirstName(),
+                nameField.getValue());
+
+        nameField.setValue("foo");
+
+        assertNotEquals("Name should be different from the item",
+                item.getFirstName(), nameField.getValue());
+
+        binding.read(item);
+
+        assertEquals("Name should be read again from the item",
+                item.getFirstName(), nameField.getValue());
+    }
 }