Track changes in collection. Tracking VO changes while looking at master Entity

[efreet007]

Is it possible to track changes in collection element properties?
For example:

    @Test
    public void shouldTrackSubordinateSalaryChanges() {
        // given:
        Javers javers = JaversBuilder.javers().build();
        Employee bob = new Employee("Bob", 9_000, "Scrum master" );
        bob.addSubordinates(new Employee("Trainee One", 1_000));
        javers.commit("hr.manager", bob);

        bob.getSubordinates().get(0).setSalary(1_200);
        javers.commit("hr.manager", bob);

        // when:
        List<Change> changes = javers.getChangeHistory(InstanceIdDTO.instanceId("Bob", Employee.class),5);

        // then:
        assertThat(changes).hasSize(2).overridingErrorMessage("Expecting NewObject change and ValueChange change for salary");

    }

[bartoszwalacik]

Not sure what do you mean. In this example you have ValueChange (salary) but on Trainee not Bob. Why you expect to see it on Bob's change history?

[efreet007]

Beacuse I want to get Bob's changelog, something like this:

commit 2.0, author: hr.manager, 2015-02-11 09:49:45
changed object: org.javers.core.examples.model.Employee/Bob
list changed on 'subordinates' property: [(0).'org.javers.core.examples.model.Employee/Trainee One'
value changed on 'salary' property: '1000' -> '1200'
commit 1.0, author: hr.manager, 2015-02-11 09:49:45
new object: org.javers.core.examples.model.Employee/Bob

Is it possible?

[bartoszwalacik]

well, I could think about some solution for that issue if Subordinate was a ValueObject (part of Boss aggregate). ValueObjects are owned by Entities and tracking changes in whole Aggregate (root Entity + ValueObject) makes sense.
Not sure if you are familiar with DDD terminology. Does it make sens in your domain?

[bartoszwalacik]

shortly, we don't plan to implement a feature to view a change history of one Entity from another Entity.
Entities are loosely coulped in JaVers, sorry but I can't help you unless you switch this dependant object to ValueObject

[efreet007]

I've switched dependant object to ValueObject, still no VO changes in changelog.. Am I doing something wrong?

VO:
public class VO {
private String name;
private int salary;
public VO(String name, int salary) {
this.name = name;
this.salary = salary;
}

public void setSalary(int salary) { this.salary = salary;    }
public int getSalary() {        return salary;    }
public void setName(String name) {        this.name = name;    }
public String getName() { return name; }

}

Employee:
...
private List vos = new ArrayList<>();
public void addVO(VO vo) { vos.add(vo); }
public void setVos(List vos) { this.vos = vos; }
public List getVOs() { return vos; }
...

Test:
@test
public void shouldTrackSubordinateSalaryChanges() {
// given:
Javers javers = JaversBuilder.javers().registerValueObject(VO.class).build();
Employee bob = new Employee("Bob", 9_000, "Scrum master" );
bob.addVO(new VO("Trainee One", 1_000));
javers.commit("hr.manager", bob);

    bob.getVOs().get(0).setSalary(1_200);
    javers.commit("hr.manager", bob);

    // when:
    List<Change> changes = javers.getChangeHistory(InstanceIdDTO.instanceId("Bob", Employee.class),5);
    String changeLog = javers.processChangeList(changes, new SimpleTextChangeLog());

    // then:
    System.out.println(changeLog);
}

Changelog:
commit 1.0, author: hr.manager, 2015-02-13 11:53:11
new object: org.javers.core.examples.model.Employee/Bob

[bartoszwalacik]

Hi, you are doing all right. Maybe I didn't express this issue clearly.
Now when you changed your domain model to Entity (master) + ValueObjects (dependant),
we have to implement in Javers a new feature, to support your use case.

With this feature, you would be able to track changes done on dependant VO while looking at master Entity.

[efreet007]

Great, I am waiting for this feature

[eladh]

Hi .

let me understand :

if i have an Object like EntityConn and the following Object is @entity with @id (javax.persistence) :
I cannot track changes of the children by looking at the EntityConn root object ?
is this behavior is for every Entity (in this example - will i be able to track endRuleMD changes from the entityConn ? (RuleMD is also is @entity with @id) .

public class EntityConn implements Serializable {  
    private Collection<EntityConn> children;  
    private RuleMD endRuleMD;
    private Map<String, List<EntityConnAttValue>> attValues;  
         ............  
}  

So - i need to do complex traversing on the Object Tree and for each @entity i need to call :
getChangeHistory(InstanceIdDTO.instanceId("instance@ID", EntityType.class), x) ???

10x
elad.

[bartoszwalacik]

Hi @eladh,
Javers treats Entities as independent beeings. To see the history of an Entity instance, you need to query by its Id.

So for example if you have two entities A and B, connected by the reference:
A->B

When B changes its state to B'
A->B'
you need to query by B.id to see this change.

What you can see from the A point of view is the reference change (when changed from A->B to A->C).

What we are working now is to tracking ValueObject changes while looking at master Entity.
So if you model B as a VO you will see changes done on it, while looking at A

[bartoszwalacik]

@efreet007, we will start working on this feature after delivering SQLRepository #67, which is almost done and available as Snapshot (requires some testing)

[eladh]

thanks :-)

[bartoszwalacik]

JQL is released in javers 1.2.0
take a look at new query API and examples
http://javers.org/documentation/jql-examples/

[bartoszwalacik]

if you are using SQL DB, there is a schema migration script