问题起因：今天在做一个EasyUI 同步树的时候,在SpringMVC中用 @ResponseBody标签将List<tree> 集合转换成Json数据的时候，出现一些原因。
问题描述：1、tree对象有个List<tree>属性需要为空，这个是做树用的，下级没值当然不能有null了
代码：
[{"id":1,"text":"权限管理 ","state":"closed ","pid":-1,"children":[{"id":2,"text":"菜单管理","state":"open","pid":1,"children":null},{"id":3,"text":"角色管理","state":"open","pid":1,"children":null},{"id":4,"text":"用户管理","state":"open","pid":1,"children":null}]},{"id":5,"text":"33","state":"open","pid":-1,"children":null}]
解决方法；在实体类上使用 @JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL) 标签 就解决了！
加上标签后：
[{"id":1,"text":"权限管理 ","state":"closed ","pid":-1,"children":[{"id":2,"text":"菜单管理","state":"open","pid":1},{"id":3,"text":"角色管理","state":"open","pid":1},{"id":4,"text":"用户管理","state":"open","pid":1}]},{"id":5,"text":"33","state":"open","pid":-1}]
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SpringMVC 中List 对象转换成Json格式 List对象中属性为NUll解决
原文：http://13145200724.blog.51cto.com/6263780/1702312