Java 只获取某些对象字段

Question

I have a POJO which looks like this:

public class Task {
    private TaskData taskData;

    String id;
    private int status;
    private int success;
    private int error;
}

class TaskData {
    transient LinkedList<String> list0;
    transient LinkedList<String> list1;
}

the lists in TaskData can be huge (over 100mb).

When getting all objects from Map<String, Task> tasksMap = new HashMap() I don't want TaskData fields to be included / be loaded. How can i achieve it?

PS It is not related to serialization.

Update: by "getting all objects" i mean, ex:

class SomeClass {
   Map<String, Task> tasksMap = new HashMap()

   SomeClass() {
      //...initialize multiple tasks with huge list0, list1..
      // => add them all
      tasksMap.put("abc0", task);
      tasksMap.put("abc1", task);
      tasksMap.put("abc2", task);
      tasksMap.put("abc3", task);
   }

   Map<String, Task> tasksMap getMap() {
      // when i get all the map's objects, i want the received `Task` objects
      // to not have `TaskData` attribute

      return tasksMap;
   }
}

Answer 1

Give the field a default value of null, then update the value later, using a setter method.

public class Task {
    private TaskData taskData;

    String id;
    private int status;
    private int success;
    private int error;
}

class TaskData {
    transient LinkedList<String> list0 = null;
    transient LinkedList<String> list1 = null;

    public void setList0(LinkedList<String> list){
        list0 = list;
    }

    public void setList1(LinkedList<String> list){
        list1 = list;
    }
}

Answer 2

I think another approach would be to create a shallow copy method, excluding the fields you don't want, and use it when populating you Map, eg :

  public Task shallowCopy() {
    Task newTask = new Task();
    newTask.id = id;
    newTask.status = status;
    ...
    return newTask;
  }