#354 - Allow saving an entity with a read-only collection-like property.

Previously a NullPointerException would be thrown.

Original pull request: #355.

Author: ljrmorgan

src/main/java/org/springframework/data/r2dbc/core/DefaultReactiveDataAccessStrategy.java

@@ -206,7 +206,7 @@ public OutboundRow getOutboundRow(Object object) {
 		for (RelationalPersistentProperty property : entity) {
 
 			SettableValue value = row.get(property.getColumnName());
-			if (shouldConvertArrayValue(property, value)) {
+			if (value != null && shouldConvertArrayValue(property, value)) {
 
 				SettableValue writeValue = getArrayValue(value, property);
 				row.put(property.getColumnName(), writeValue);

src/test/java/org/springframework/data/r2dbc/core/ReactiveDataAccessStrategyTestSupport.java

@@ -36,6 +36,7 @@
 
 import org.junit.Test;
 
+import org.springframework.data.annotation.ReadOnlyProperty;
 import org.springframework.data.r2dbc.dialect.R2dbcDialect;
 import org.springframework.data.r2dbc.mapping.SettableValue;
 import org.springframework.data.relational.core.sql.SqlIdentifier;
@@ -177,6 +178,16 @@ public void shouldReadAndWriteBinary() {
 		testType(PrimitiveTypes::setBinary, PrimitiveTypes::getBinary, "hello".getBytes(), "binary");
 	}
 
+	@Test // gh-354
+	public void shouldNotWriteReadOnlyFields() {
+		TypeWithReadOnlyFields toSave = new TypeWithReadOnlyFields();
+		toSave.setWritableField("writable");
+		toSave.setReadOnlyField("readonly");
+		toSave.setReadOnlyArrayField("readonly_array".getBytes());
+		assertThat(getStrategy().getOutboundRow(toSave))
+				.containsOnlyKeys(SqlIdentifier.unquoted("writable_field"));
+	}
+
 	private <T> void testType(BiConsumer<PrimitiveTypes, T> setter, Function<PrimitiveTypes, T> getter, T testValue,
 			String fieldname) {
 
@@ -235,4 +246,13 @@ static class PrimitiveTypes {
 
 		UUID uuid;
 	}
+
+	@Data
+	static class TypeWithReadOnlyFields {
+		String writableField;
+		@ReadOnlyProperty
+		String readOnlyField;
+		@ReadOnlyProperty
+		byte[] readOnlyArrayField;
+	}
 }