相用json-lib 過濾屬性，網上搜了一下，都是過濾第一級別的，需要重寫 config，filed 什么的。覺得很麻煩，然后搜了下別的實現方案，阿里巴巴的 fastjson 很不錯

實現如下：

SimplePRopertyPreFilter filter = new SimplePropertyPreFilter(TTown.class, "id","townname");      response.getWriter().write(JSONObject.toJSONString(townList,filter)); 只要指定二級屬性的類名就可以了，很方便。但是如果就想用json-lib 怎么弄呢？
我不想改config ，filter什么的，于是自己寫
public class Test {		public static void main(String[] args) throws Exception {						Entity e1 = new Entity();		e1.setAge(1);		e1.setId(1);		e1.setName("e1");		e1.setSex("male");				Entity e2 = new Entity();		e2.setAge(2);		e2.setId(2);		e2.setName("e2");		e2.setSex("female");				List<Entity> list = new ArrayList<Entity>();		list.add(e1);		list.add(e2);				Map map = new HashMap();		map.put("id", 1);		map.put("name", "bruce");		map.put("list", list);				JSONObject json = JSONObject.fromObject( map );  		System.out.println(json.toString());		//-----------------------------------		String[] names = {"sex"};		map = convert(map,names);		System.out.println("---------------------");		json = JSONObject.fromObject( map );  		System.out.println(json.toString());	}		 static Map convert(Map para,String[] names) throws Exception{				List<Map> result = new ArrayList<Map>();		List list = (List) para.get("list");				for(Object ob :list){			Map map = new HashMap();			Field[] fs = ob.getClass().getDeclaredFields();			for(Field f : fs){				if(!contains(names, f.getName())){					f.setaccessible(true); //設置些屬性是可以訪問的  			        Object val = f.get(ob);					map.put(f.getName(), val);				}			}			result.add(map);		}				para.put("list", result);		return para;	}		static boolean contains(String[] strs ,String str){		if(null == strs || strs.length == 0){			return false;		}				for(int i=0;i<strs.length;i++){			if(strs[i].equals(str)){				return true;			}		}		return false;	}	}大體思路是 將list 中的實體遍歷，利用反射過濾屬性，生成一個新的map .塞回list中。然后再把新的list賦值給原始的map。生成json 。運行結果如下：
{"name":"bruce","id":1,"list":[{"sex":"male","name":"e1","id":1,"age":1},{"sex":"female","name":"e2","id":2,"age":2}]}---------------------{"name":"bruce","id":1,"list":[{"name":"e1","id":1,"age":1},{"name":"e2","id":2,"age":2}]}
將二級屬性list 中的 sex 屬性過濾掉了