Constructors or Static Methods for Loading and Saving Objects?

Question

I'm trying to decide whether it is better to use static methods for loading/saving objects, or use constructor/instance methods instead.

So, say for object Project, the instance version would be

public Project(path) { // Load project here }
public void Save(path) { // Save project here }

And the static version would be

public static Project Load(path) { // Load project and return result }
public static void Save(path, proj) { // Save project }

So, which do you prefer?

Answer 1

Neither. Favor extracting persistence logic from your domain model and into a separate layer of classes.

(from a comment left in ChrisW's answer) Regarding the details of the domain object leaking into another class: you can restrict the visibility of those details, if your language permits, by using package-privacy/internal access. Alternatively, you can use a DTO approach.

Answer 2

If there is no state to be maintained, only behavior, then use the static approach. However, if the Project object needs to have state, then the constructor/instance method should be used.