Serialization of domain objects in MapDB

Question

In my mapdb application, for example, I have a simple domain object Course:

import java.io.Serializable;

class Course implements Serializable {
  private static final long serialVersionUID = 1L;
  String cID;
  String name;
  String teacherName;
  String departmentName;
  public Course(String name) {
    this.name = name;
    System.out.println("Update: added course \"" + name);
  }
}

By trial and error I added the implements Serializable, the serialVersionID and my own domain key, cID. All seems to work. But here's my code to store that into MapDB:

NavigableMap<String, Course> courses;
courses = db.treeMap("courses", Serializer.STRING, Serializer.JAVA).createOrOpen();

Which gives a warning:

Type safety: The expression of type BTreeMap needs unchecked
conversion to conform to NavigableMap<String,Course>

I don't understand that error, but I believe it has to do with my serialization as Serializer.JAVA. What is going on, or what I am doing wrong?

score 0 · Answer 1 · answered Apr 20 '17 at 04:46

0

Add generics to treemap method:

     courses = db.<String, Course>treeMap

answered Apr 20 '17 at 04:46

Jan Kotek

1,084
7
4

this is not java code and it doesn't build, please paste full code – Stepan Yakovenko Oct 13 '18 at 09:17
4

That's valid Java. You don't usually see types with method references, but the language allows it. – mrog Mar 22 '19 at 18:19

Serialization of domain objects in MapDB

1 Answers1