public String formatJson(Object obj) {

    	com.alibaba.fastjson.JSONObject json=(com.alibaba.fastjson.JSONObject)JSON.toJSON(obj);

	    //定制序列化

	    SerializeFilter[] filter = new SerializeFilter[]{

	        new ValueFilter() {

	            @Override

	            public Object process(Object object, String name, Object value) {

	                if (value == null || value == "") {

	                    return "";

	                }

	                return value;

	            }

	        }

	    };

	    return JSON.toJSONString(json, filter, SerializerFeature.WriteMapNullValue,

	        SerializerFeature.WriteNullStringAsEmpty,

	        SerializerFeature.WriteNullListAsEmpty,

	        SerializerFeature.WriteDateUseDateFormat);

    }