fix ctor is null when encoding issue

Author: taowen

src/main/java/com/jsoniter/spi/Config.java

@@ -343,6 +343,9 @@ private void detectStaticFactory(ClassDescriptor desc, List<Method> allMethods)
     }
 
     private void detectCtor(ClassDescriptor desc) {
+        if (desc.ctor == null) {
+            return;
+        }
         for (Constructor ctor : desc.clazz.getDeclaredConstructors()) {
             JsonCreator jsonCreator = getJsonCreator(ctor.getAnnotations());
             if (jsonCreator == null) {

src/test/java/com/jsoniter/TestAnnotationJsonProperty.java

@@ -1,5 +1,6 @@
 package com.jsoniter;
 
+import com.jsoniter.annotation.JsonCreator;
 import com.jsoniter.annotation.JsonMissingProperties;
 import com.jsoniter.annotation.JsonProperty;
 import com.jsoniter.fuzzy.StringIntDecoder;
@@ -141,4 +142,20 @@ public void test_getter_and_setter() throws IOException {
         TestObject9 entity = JsonIterator.deserialize(test, TestObject9.class);
         assertEquals("hi", entity.getField1());
     }
+
+    public static class TestObject10 {
+        public int field;
+
+        @JsonCreator
+        public TestObject10(@JsonProperty("hello") int field) {
+            this.field = field;
+        }
+    }
+
+    public void test_creator_with_json_property() {
+        String input = "{\"hello\":100}";
+        TestObject10 obj = JsonIterator.deserialize(input, TestObject10.class);
+        assertEquals(100, obj.field);
+        assertEquals("{\"field\":100}", JsonStream.serialize(obj));
+    }
 }