C++解析Json的方法详解【jsoncpp】

const char* str = "{\"uploadid\": \"UP000000\",\"code\": 100,\"msg\": \"\",\"files\": \"\"}";
Json::Reader reader;
Json::Value root;
if (reader.parse(str, root)) // reader将Json字符串解析到root，root将包含Json里所有子元素
{
  std::string upload_id = root["uploadid"].asString(); // 访问节点，upload_id = "UP000000"
  int code = root["code"].asInt();  // 访问节点，code = 100
}

int ReadJsonFromFile(const char* filename)
{
  Json::Reader reader;// 解析json用Json::Reader
  Json::Value root; // Json::Value是一种很重要的类型，可以代表任意类型。如int, string, object, array
  std::ifstream is;
  is.open (filename, std::ios::binary );
  if (reader.parse(is, root, FALSE))
  {
    std::string code;
    if (!root["files"].isNull()) // 访问节点，Access an object value by name, create a null member if it does not exist.
      code = root["uploadid"].asString();
    code = root.get("uploadid", "null").asString();// 访问节点，Return the member named key if it exist, defaultValue otherwise.
    int file_size = root["files"].size(); // 得到"files"的数组个数
    for(int i = 0; i < file_size; ++i) // 遍历数组
    {
      Json::Value val_image = root["files"][i]["images"];
      int image_size = val_image.size();
      for(int j = 0; j < image_size; ++j)
      {
        std::string type = val_image[j]["type"].asString();
        std::string url = val_image[j]["url"].asString();
        printf("type : %s, url : %s \n", type.c_str(), url.c_str());
      }
    }
  }
  is.close();
  return 0;
}

void WriteJsonData(const char* filename)
{
  Json::Reader reader;
  Json::Value root; // Json::Value是一种很重要的类型，可以代表任意类型。如int, string, object, array
  std::ifstream is;
  is.open (filename, std::ios::binary );
  if (reader.parse(is, root))
  {
    Json::Value arrayObj;  // 构建对象
    Json::Value new_item, new_item1;
    new_item["date"] = "2011-11-11";
    new_item1["time"] = "11:11:11";
    arrayObj.append(new_item); // 插入数组成员
    arrayObj.append(new_item1); // 插入数组成员
    int file_size = root["files"].size();
    for(int i = 0; i < file_size; ++i)
      root["files"][i]["exifs"] = arrayObj;  // 插入原json中
    std::string out = root.toStyledString();
    // 输出无格式json字符串
    Json::FastWriter writer;
    std::string strWrite = writer.write(root);
    std::ofstream ofs;
    ofs.open("test_write.json");
    ofs << strWrite;
    ofs.close();
  }
  is.close();
}

Json::Value root;
Json::Reader reader;

Value::~Value() {
 switch (type_) {
 case nullValue:
 case intValue:
 case uintValue:
 case realValue:
 case booleanValue:
  break;
 case stringValue:
  if (allocated_)
   releaseStringValue(value_.string_);
  break;
 case arrayValue:
 case objectValue:
  delete value_.map_;//!!!!!!
  break;
 default:
  JSON_ASSERT_UNREACHABLE;
 }

int getRebalancing(string str, Json::Value root, Json::Reader reader) ;
int main() {
  Json::Value root;
  Json::Reader reader;
  while(1){
    getRebalancing(string::str, root, reader);
    //do something
    }
  return 0;
}