fix

Author: binarywang

weixin-java-mp/src/main/java/me/chanjar/weixin/mp/util/json/WxMpMassPreviewMessageGsonAdapter.java

@@ -16,7 +16,7 @@ public class WxMpMassPreviewMessageGsonAdapter implements JsonSerializer<WxMpMas
   @Override
   public JsonElement serialize(WxMpMassPreviewMessage wxMpMassPreviewMessage, Type type, JsonSerializationContext jsonSerializationContext) {
     JsonObject jsonObject = new JsonObject();
-    jsonObject.addProperty("towxname", wxMpMassPreviewMessage.getToWxUsername());
+    jsonObject.addProperty("towxname", wxMpMassPreviewMessage.getToWxUserName());
     jsonObject.addProperty("touser", wxMpMassPreviewMessage.getToWxUserOpenid());
     if (WxConsts.MASS_MSG_NEWS.equals(wxMpMassPreviewMessage.getMsgType())) {
       JsonObject news = new JsonObject();