详解Java去除json数据中的null空值问题

@JsonInclude(JsonInclude.Include.NON_NULL)public class User implements Serializable {   private String username;   private String password;   @JsonInclude(JsonInclude.Include.NON_NULL)  private String token; }

spring：   jackson:    default-property-inclusion: non_null

package com.dunyun.openapi.util.json; import java.util.ArrayList;import java.util.List;import com.alibaba.fastjson.JSONArray;import com.alibaba.fastjson.JSONObject;import com.dunyun.platform.util.StringUtil; public class RemoveNullAttr {  public static void main(String[] args){    String s="{/"employees/": [{ /"firstName/":/"/" , /"lastName/":/"Doe/" },{ /"firstName/":/"/" , /"lastName/":/"Smith/" },{ /"firstName/":/"Peter/" , /"lastName/":/"Jones/" }]}";  String a="{ /"firstName/":/"John/" , /"lastName/":/"/" }";  String b="{ /"firstName/":/"/" , /"lastName/":/"Doe/" }";  String test="{/"ka/":/"va/",/"kb/":{/"kbk/":/"kbv/",/"kbkk/":/"/",/"kbkkk/":{/"aaa/":/"bbb/",/"bbb/":/"/"},/"suzu/":[{/"sz/":/"sz/",/"szk/":/"/"}]},/"kc/":/"kcv/"}";  JSONObject js=JSONObject.parseObject(test);      RemoveNullAttr r=new RemoveNullAttr();  Object o=r.traverseJson(js);  System.out.println(o);  }     private Object traverseJson(Object json) {    // check null    if (json == null) {      return null;    }        try {            if (json instanceof JSONObject) {// if json is a Map                JSONObject jsonObj = (JSONObject)json;        List keyList=new ArrayList();        for(String k:jsonObj.keySet()){          String value=jsonObj.get(k).toString();          if(StringUtil.isEmpty(value)){            keyList.add(k);            //jsonObj.remove(k);          }else{            if(isJsonObj(value)){              jsonObj.put(k, traverseJson(JSONObject.parseObject(value)));            }else{if(isJsonArr(value)){              //value=;              jsonObj.put(k, traverseJson(JSONArray.parseArray(value))) ;            }                          }                      }        }        for(String k:keyList){          jsonObj.remove(k);        }                return jsonObj;              }      else if (json instanceof JSONArray) {// if json is an Array                JSONArray jsonArr = (JSONArray)json;        int len = jsonArr.size();        for (int i = 0; i < len; ++i) {          // TODO: do something here          jsonArr.set(i, traverseJson(jsonArr.get(i)));        }//        return retArr;//        //      } else {// if json is just a raw element//        //        // TODO: do something here//        return json;        return jsonArr;//              }          } catch (Exception e) {      e.printStackTrace();// deal Exception or throw it    }        return null;  }    public boolean isJsonObj(Object o){    try{      JSONObject js=JSONObject.parseObject(o.toString());      return true;          }catch(Exception e){      return false;    }  }    public boolean isJsonArr(Object o){    try{      JSONArray js=JSONArray.parseArray(o.toString());      return true;          }catch(Exception e){      return false;    }  }      }