Fixed issue #130 Default Parameter Values when JSON value is null (#259)

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinValueInstantiator.kt

@@ -89,11 +89,15 @@ internal class KotlinValueInstantiator(
                 return@forEachIndexed
             }
 
-            var paramVal = if (!isMissing || paramDef.isPrimitive() || jsonProp.hasInjectableValueId()) {
-                buffer.getParameter(jsonProp)
+            var paramVal:Any?
+            if (!isMissing || paramDef.isPrimitive() || jsonProp.hasInjectableValueId()) {
+                paramVal = buffer.getParameter(jsonProp)
+                if (paramVal == null && paramDef.isOptional) {
+                    return@forEachIndexed
+                }
             } else {
                 // trying to get suitable "missing" value provided by deserializer
-                jsonProp.valueDeserializer?.getNullValue(ctxt)
+                paramVal = jsonProp.valueDeserializer?.getNullValue(ctxt)
             }
 
             if (paramVal == null && ((nullToEmptyCollection && jsonProp.type.isCollectionLikeType) || (nullToEmptyMap && jsonProp.type.isMapLikeType))) {

src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/NullToDefault.kt

@@ -0,0 +1,56 @@
+package com.fasterxml.jackson.module.kotlin.test
+
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
+import org.junit.Assert
+import org.junit.Test
+
+class NullToDefault {
+
+	private fun createMapper() = jacksonObjectMapper()
+
+	private data class TestClass(val sku: Int = -1,
+								 val text: String,
+								 val name: String = "",
+								 val images: String?,
+								 val language: String = "uk",
+								 val attribute: Int = 0,
+								 val order: Int = -1)
+
+	@Test
+	fun shouldUseDefault() {
+		val item = createMapper().readValue<TestClass>("{\n" +
+				"            \"sku\": \"974\",\n" +
+				"            \"text\": \"plain\",\n" +
+				"            \"name\": null,\n" +
+				"            \"images\": null,\n" +
+				"            \"attribute\": \"19\",\n" +
+				"            \"new_item\": \"Composition: 100% polyester; 1.75 \"" +
+				"        }")
+
+		Assert.assertTrue(item.sku == 974)
+		Assert.assertTrue(item.text == "plain")
+		Assert.assertTrue(item.name != null)
+		Assert.assertTrue(item.images == null)
+		Assert.assertTrue(item.language == "uk")
+		Assert.assertTrue(item.attribute == 19)
+		Assert.assertTrue(item.order == -1)
+	}
+
+	@Test
+	fun errorIfNotDefault() {
+		val item = createMapper().readValue<TestClass>("{\n" +
+				"            \"sku\": \"974\",\n" +
+				"            \"text\": null,\n" +
+				"            \"attribute\": \"19\",\n" +
+				"            \"name\": null,\n" +
+				"            \"new_item\": \"Composition: 100% polyester; 1.75 \"" +
+				"        }")
+
+		Assert.assertTrue(item.sku == 974)
+		Assert.assertTrue(item.language == "uk")
+		Assert.assertTrue(item.attribute == 19)
+		Assert.assertTrue(item.name != null)
+		Assert.assertTrue(item.order == -1)
+	}
+}