List<String> strList=list.stream.map(T::get).collect(Collectors.toList);

List<AppModel> list=new ArrayList<>();
Map<String, List<AppModel>> groupByCategoryList = appModelList
    .stream()
    .collect(
    Collectors
    .groupingBy(AppModel::getModelCategory)
);

//先构造Map<String,Person>得到innerType,第一个参数为外层对象HashMap，第二个参数为String,第三个参数为Person
JavaType innerType = mapper.getTypeFactory().constructParametricType(HashMap.class, String.class, Person.class);
//再构造List<innerType> 
JavaType resultType = mapper.getTypeFactory().constructParametricType(ArrayList.class, innerType);
//反序列化
List<Map<String, Person>> result2 = mapper.readValue(s, resultType);