最近在实习的时候，需要将多层嵌套的json转换为单层的json。并且把json进行格式化。于是参照网上的网上的方法使用谷歌的gson利用递归的实现了多层json转换为单层的json。如
{"code":200, "message":"ok", "data":"{\"id\":131,\"appId\":6,\"versionCode\":6014000}"}转换为：
{
"code": 200,
"data.appId": 6,
"data.versionCode": 6014000,
"data.id": 131,
"message": "ok"
}使用gson中的JsonParser来做
/**
* 使用Gson拍平json字符串，即当有多层json嵌套时，可以把多层的json拍平为一层
* @param map
* @param json
* @param parentKey
*/
public static void parseJson2Map(Map map, String json, String parentKey){
JsonElement jsonElement = new JsonParser().parse(json);
if (jsonElement.isJsonObject()) {
JsonObject jsonObject = jsonElement.getAsJsonObject();
parseJson2Map(map,jsonObject,parentKey);
//传入的还是一个json数组
}else if (jsonElement.isJsonArray()){
JsonArray jsonArray = jsonElement.getAsJsonArray();
Iterator<JsonElement> iterator = jsonArray.iterator();
while (iterator.hasNext()){
parseJson2Map(map,iterator.next().getAsJsonObject(),parentKey);
}
}else if (jsonElement.isJsonPrimitive()){
System.out.println("please check the json format!");
}else if (jsonElement.isJsonNull()){
}
}
public static void parseJson2Map(Map map,JsonObject jsonObject,String parentKey){
for (Map.Entry<String, JsonElement> object : jsonObject.entrySet()) {
String key = object.getKey();
JsonElement value = object.getValue();
String fullkey = (null == parentKey || parentKey.trim().equals("")) ? key : parentKey.trim() + "." + key;
//判断对象的类型，如果是空类型则安装空类型处理
if (value.isJsonNull()){
map.put(fullkey,null);
continue;
//如果是JsonObject对象则递归处理
}else if (value.isJsonObject()){
parseJson2Map(map,value.getAsJsonObject(),fullkey);
//如果是JsonArray数组则迭代，然后进行递归
}else if (value.isJsonArray()){
JsonArray jsonArray = value.getAsJsonArray();
Iterator<JsonElement> iterator = jsonArray.iterator();
while (iterator.hasNext()) {
JsonElement jsonElement1 = iterator.next();
parseJson2Map(map, jsonElement1.getAsJsonObject(), fullkey);
}
continue;
// 如果是JsonPrimitive对象则获取当中的值,则还需要再次进行判断一下
}else if (value.isJsonPrimitive()){
try {
JsonElement element = new JsonParser().parse(value.getAsString());
if (element.isJsonNull()){
map.put(fullkey,value.getAsString());
}else if (element.isJsonObject()) {
parseJson2Map(map, element.getAsJsonObject(), fullkey);
} else if (element.isJsonPrimitive()) {
JsonPrimitive jsonPrimitive = element.getAsJsonPrimitive();
if (jsonPrimitive.isNumber()) {
map.put(fullkey, jsonPrimitive.getAsNumber());
} else {
map.put(fullkey, jsonPrimitive.getAsString());
}
} else if (element.isJsonArray()) {
JsonArray jsonArray = element.getAsJsonArray();
Iterator<JsonElement> iterator = jsonArray.iterator();
while (iterator.hasNext()) {
parseJson2Map(map, iterator.next().getAsJsonObject(), fullkey);
}
}
}catch (Exception e){
map.put(fullkey,value.getAsString());
}
}
}
}经过这个程序的处理，则会把json串转换为一个map对象。再把一个map对象转换为一个规格化的json串。
/**
*把拍平后的json进行格式化处理，输出标准的json格式
* @param uglyJSONString
* @return
*/
public static String jsonFormatter(String uglyJSONString){
Map<String,Object> map = new HashMap<>();
parseJson2Map(map,uglyJSONString,null);
JSONObject jsonObject = JSONObject.fromObject(map);
uglyJSONString = jsonObject.toString();
Gson gson = new GsonBuilder().setPrettyPrinting().create();
JsonParser jp = new JsonParser();
JsonElement je = jp.parse(uglyJSONString);
String prettyJsonString = gson.toJson(je);
///System.out.println(prettyJsonString);
return prettyJsonString;
}测试结果：
public static void main(String[] args){
String json = "{\"code\":200, \"message\":\"ok\", \"data\":\"{\\\"id\\\":131,\\\"appId\\\":6,\\\"versionCode\\\":6014000}\"}";
String test = "{" + "\"hello\": \"sweetzcc\"," +
"\"topic\": \"gjs\"," +
"\"Id\": \"180605Ceb8NB\"," +
"\"Type\": \"REG\"," +
"\"Time\": \"2018-06-05 10:02:24\"," +
"\"sweetzcc\": \"{\\\"needUpdate\\\":true,\\\"Info\\\":\\\"{\\\\\\\"apple\\\\\\\":\\\\\\\"BB199DA64A7692E927722BFD1CA\\\\\\\",\\\\\\\"token\\\\\\\":null,\\\\\\\"uniqueId\\\\\\\":\\\\\\\"868387\\\\\\\",\\\\\\\"pushSweetToken\\\\\\\":\\\\\\\"a968\\\\\\\",\\\\\\\"device\\\\\\\":\\\\\\\"android\\\\\\\",\\\\\\\"systemName\\\\\\\":\\\\\\\"Re\\\\\\\",\\\\\\\"systemV\\\\\\\":\\\\\\\"7.0\\\\\\\",\\\\\\\"pVersion\\\\\\\":\\\\\\\"4.9\\\\\\\",\\\\\\\"key\\\\\\\":\\\\\\\"63e78ea58\\\\\\\",\\\\\\\"chan\\\\\\\":\\\\\\\"net\\\\\\\",\\\\\\\"push\\\\\\\":\\\\\\\"4\\\\\\\",\\\\\\\"userName\\\\\\\":null,\\\\\\\"product\\\\\\\":\\\\\\\"sweet\\\\\\\",\\\\\\\"crime\\\\\\\":1528,\\\\\\\"update1\\\\\\\":15281}\\\"}\"" +
"}";
String array = "{'name':'111','child':[{'child':[{'name':'333'}]},{'name':'2221'}]}" ;
System.out.println(jsonFormatter(test));
}{
"sweetzcc.Info.pushSweetToken": "a968",
"sweetzcc.Info.systemName": "Re",
"sweetzcc.Info.device": "android",
"sweetzcc.Info.systemV": 7,
"Time": "2018-06-05 10:02:24",
"sweetzcc.Info.chan": "net",
"sweetzcc.Info.product": "sweet",
"sweetzcc.Info.apple": "BB199DA64A7692E927722BFD1CA",
"Type": "REG",
"sweetzcc.Info.pVersion": 4.9,
"topic": "gjs",
"sweetzcc.needUpdate": "true",
"sweetzcc.Info.uniqueId": 868387,
"hello": "sweetzcc",
"Id": "180605Ceb8NB",
"sweetzcc.Info.update1": 15281,
"sweetzcc.Info.push": 4,
"sweetzcc.Info.key": "63e78ea58",
"sweetzcc.Info.crime": 1528
}
{
"code": 200,
"data.appId": 6,
"data.versionCode": 6014000,
"data.id": 131,
"message": "ok"
}
{
"name": 111,
"child.child.name": 333,
"child.name": 2221
}
参考：
[]: https://blog.csdn.net/qq_24236769/article/details/77127318 "嵌套（任意层）JSON解析转换为Map"