backport alibaba#1222 from standard version.

wenshao · wenshao · commit f3585af53e2d · 2017-07-02T00:11:46.000+08:00
diff --git a/src/main/java/com/alibaba/fastjson/util/FieldInfo.java b/src/main/java/com/alibaba/fastjson/util/FieldInfo.java
@@ -12,6 +12,7 @@
 import java.lang.reflect.TypeVariable;
 import java.util.Arrays;
 
+import com.alibaba.fastjson.JSONAware;
 import com.alibaba.fastjson.annotation.JSONField;
 
 public class FieldInfo implements Comparable<FieldInfo> {
@@ -55,7 +56,7 @@ public FieldInfo(String name, //
         this.field = field;
         this.ordinal = ordinal;
         
-        isEnum = fieldClass.isEnum();
+        isEnum = fieldClass.isEnum() && !JSONAware.class.isAssignableFrom(fieldClass);
         
         fieldAnnotation = null;
         methodAnnotation = null;
@@ -208,7 +209,7 @@ public FieldInfo(String name, //
                 this.fieldClass = TypeUtils.getClass(genericFieldType);
                 this.fieldType = genericFieldType;
                 
-                isEnum = fieldClass.isEnum();
+                isEnum = fieldClass.isEnum() && !JSONAware.class.isAssignableFrom(fieldClass);
                 return;
             }
         }
@@ -229,7 +230,9 @@ public FieldInfo(String name, //
         this.fieldType = genericFieldType;
         this.fieldClass = fieldClass;
 
-        isEnum = (!fieldClass.isArray()) && fieldClass.isEnum();
+        isEnum = (!fieldClass.isArray())
+                && fieldClass.isEnum()
+                && !JSONAware.class.isAssignableFrom(fieldClass);
     }
 
     public static Type getFieldType(Class<?> clazz, Type type, Type fieldType) {
diff --git a/src/test/java/com/alibaba/json/bvt/issue_1200/Issue1222.java b/src/test/java/com/alibaba/json/bvt/issue_1200/Issue1222.java
@@ -0,0 +1,30 @@
+package com.alibaba.json.bvt.issue_1200;
+
+import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson.JSONAware;
+import com.alibaba.fastjson.serializer.SerializerFeature;
+import junit.framework.TestCase;
+
+/**
+ * Created by wenshao on 01/06/2017.
+ */
+public class Issue1222 extends TestCase {
+    public void test_for_issue() throws Exception {
+        Model model = new Model();
+        model.type = Type.A;
+        String text = JSON.toJSONString(model, SerializerFeature.WriteEnumUsingToString);
+        assertEquals("{\"type\":\"TypeA\"}", text);
+    }
+
+    public static class Model {
+        public Type type;
+    }
+
+    public static enum Type implements JSONAware {
+        A, B;
+
+        public String toJSONString() {
+            return "\"Type" + this.name() + "\"";
+        }
+    }
+}
