diff --git a/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/DataClass.kt b/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/DataClass.kt
index c2d0e9fb..3b612845 100755
--- a/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/DataClass.kt
+++ b/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/DataClass.kt
@@ -1,11 +1,7 @@
 package wu.seal.jsontokotlin.model.classscodestruct
 
 import wu.seal.jsontokotlin.interceptor.IKotlinClassInterceptor
-import wu.seal.jsontokotlin.utils.LogUtil
-import wu.seal.jsontokotlin.utils.getCommentCode
-import wu.seal.jsontokotlin.utils.getIndent
-import wu.seal.jsontokotlin.utils.toAnnotationComments
-import java.lang.IllegalStateException
+import wu.seal.jsontokotlin.utils.*
 
 data class DataClass(
         val annotations: List<Annotation> = listOf(),
@@ -53,7 +49,8 @@ data class DataClass(
                     else -> it
                 }
                 LogUtil.i("replace type: ${property.type} to ${newTypObj.name}")
-                return@let property.copy(type = newTypObj.name, typeObject = newTypObj)
+                val typeSuffix = if (property.type.endsWith("?")) "?" else ""
+                return@let property.copy(type = "${newTypObj.name}$typeSuffix", typeObject = newTypObj)
             }
         }
 
@@ -77,15 +74,12 @@ data class DataClass(
                 append("data class ").append(name).append("(").append("\n")
             }
             properties.forEachIndexed { index, property ->
-                val code = property.getCode()
+                val addIndentCode = property.getCode().addIndent(indent)
                 val commentCode = getCommentCode(property.comment)
                 if (fromJsonSchema && commentCode.isNotBlank()) {
-                    append("/**\n * $commentCode\n */\n".split("\n").joinToString("\n") { indent + it })
-                    append(code)
-                }else{
-                    val addIndentCode = code.split("\n").joinToString("\n") { indent + it }
+                    append(commentCode.toAnnotationComments(indent))
                     append(addIndentCode)
-                }
+                } else append(addIndentCode)
                 if (index != properties.size - 1) append(",")
                 if (!fromJsonSchema && commentCode.isNotBlank()) append(" // ").append(commentCode)
                 append("\n")
@@ -100,14 +94,13 @@ data class DataClass(
                 append(" {")
                 append("\n")
                 val nestedClassesCode = nestedClasses.joinToString("\n\n") { it.getCode() }
-                append(nestedClassesCode.lines().joinToString("\n") { if (it.isNotBlank()) "$indent$it" else it })
+                append(nestedClassesCode.addIndent(indent))
                 append("\n")
                 append("}")
             }
         }
     }
 
-
     override fun <T : KotlinClass> applyInterceptors(enabledKotlinClassInterceptors: List<IKotlinClassInterceptor<T>>): KotlinClass {
         val newProperties = mutableListOf<Property>()
         properties.forEach {
diff --git a/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/Property.kt b/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/Property.kt
index 03853507..034808a3 100755
--- a/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/Property.kt
+++ b/src/main/kotlin/wu/seal/jsontokotlin/model/classscodestruct/Property.kt
@@ -10,8 +10,7 @@ data class Property(
         val value: String = "",
         val comment: String = "",
         val typeObject: KotlinClass,
-        private var separatorBetweenAnnotationAndProperty: String = "\n",
-        val nullable: Boolean = false
+        private var separatorBetweenAnnotationAndProperty: String = "\n"
 ) {
     fun letLastAnnotationStayInSameLine() {
         separatorBetweenAnnotationAndProperty = " "
@@ -27,7 +26,6 @@ data class Property(
                 }
             }
             append(keyword).append(" ").append(name).append(": ").append(type)
-            if(nullable) append("?")
             if (value.isNotBlank()) {
                 append(" = ").append(value)
             }
diff --git a/src/main/kotlin/wu/seal/jsontokotlin/utils/Extensions.kt b/src/main/kotlin/wu/seal/jsontokotlin/utils/Extensions.kt
index 1a064a25..bf3f03a8 100755
--- a/src/main/kotlin/wu/seal/jsontokotlin/utils/Extensions.kt
+++ b/src/main/kotlin/wu/seal/jsontokotlin/utils/Extensions.kt
@@ -24,6 +24,7 @@ fun String.numberOf(subString: String): Int {
 private fun JsonArray.onlyHasOneElement(): Boolean {
     return size() == 1
 }
+
 /**
  * array only has object element
  */
@@ -35,6 +36,7 @@ fun JsonArray.allItemAreNullElement(): Boolean {
     }
     return true
 }
+
 /**
  * array only has object element
  */
@@ -196,11 +198,15 @@ fun JsonPrimitive.toKotlinClass(): KotlinClass {
 /**
  * convert string into annotation comments format,TODO need automatic line wrapping
  */
-fun String.toAnnotationComments():String{
-    return if(this.isBlank()) "" else{
-        StringBuffer().append("/**\n")
-                .append(" * $this\n")
-                .append(" */\n")
+fun String.toAnnotationComments() = this.toAnnotationComments("")
+
+fun String.toAnnotationComments(indent: String): String {
+    return if (this.isBlank()) "" else {
+        StringBuffer().append("$indent/**\n")
+                .append("$indent * $this\n")
+                .append("$indent */\n")
                 .toString()
     }
-}
\ No newline at end of file
+}
+
+fun String.addIndent(indent: String): String = this.lines().joinToString("\n") { if (it.isBlank()) it else "$indent$it" }
\ No newline at end of file
diff --git a/src/main/kotlin/wu/seal/jsontokotlin/utils/classgenerator/DataClassGeneratorByJSONSchema.kt b/src/main/kotlin/wu/seal/jsontokotlin/utils/classgenerator/DataClassGeneratorByJSONSchema.kt
index 7b828bdf..bc2021c2 100755
--- a/src/main/kotlin/wu/seal/jsontokotlin/utils/classgenerator/DataClassGeneratorByJSONSchema.kt
+++ b/src/main/kotlin/wu/seal/jsontokotlin/utils/classgenerator/DataClassGeneratorByJSONSchema.kt
@@ -58,14 +58,13 @@ class DataClassGeneratorByJSONSchema(private val rootClassName: String, private
             val (jsonClassName, realDef) = getRealDefinition(jsonProp)
             resolveTypeClass(realDef.typeString, jsonClassName, realDef, propertyName)
         }
-        val value = if (isRequired) getDefaultValue(typeClass.name) else null
+        val value = if (isRequired || !jsonProp.isTypeNullable) getDefaultValue(typeClass.name) else null
         return Property(
                 originName = propertyName,
                 originJsonValue = value,
-                type = typeClass.name + if (jsonProp.isTypeNullable) "?" else "",
+                type = typeClass.name,
                 comment = jsonProp.description ?: "",
-                typeObject = typeClass,
-                nullable = jsonProp.isTypeNullable
+                typeObject = typeClass
         )
     }
 
diff --git a/src/test/kotlin/wu/seal/jsontokotlin/KotlinCodeMakerTest.kt b/src/test/kotlin/wu/seal/jsontokotlin/KotlinCodeMakerTest.kt
index bb6cf776..1945eeba 100755
--- a/src/test/kotlin/wu/seal/jsontokotlin/KotlinCodeMakerTest.kt
+++ b/src/test/kotlin/wu/seal/jsontokotlin/KotlinCodeMakerTest.kt
@@ -351,7 +351,7 @@ data class TestData(
             )
         }""".trimIndent()
       val dataClass = KotlinClassMaker("TestData", json).makeKotlinClass() as DataClass
-      dataClass.properties[3].originJsonValue.should.be.`null`
+      dataClass.properties[3].originJsonValue.should.be.equal("Nested()")
       val result = dataClass.getCode()
     result.trim().should.be.equal(expected)
   }
diff --git a/src/test/kotlin/wu/seal/jsontokotlin/regression/Issue269Test.kt b/src/test/kotlin/wu/seal/jsontokotlin/regression/Issue269Test.kt
index c971fa0c..26241ee5 100644
--- a/src/test/kotlin/wu/seal/jsontokotlin/regression/Issue269Test.kt
+++ b/src/test/kotlin/wu/seal/jsontokotlin/regression/Issue269Test.kt
@@ -1530,7 +1530,7 @@ class Issue269Test {
         data class Variant(
             val id: Int,
             val color: String,
-            val size: Int,
+            val size: Int?,
             val price: Int
         )