问题
When comparing two objects of the same size, Javers compares 1-to-1. However, if a new change is added such as new row to one of the objects, the comparison reports changes that are NOT changes. Is it possible to have Javers ignore the addition/deletion for the sake of just comparing like objects?
Basically the indices get out of sync.
Row Name Age Phone(Cell/Work)
1 Jo 20 123
2 Sam 25 133
3 Rick 30 152
4 Rick 30 145
New List
Row Name Age Phone(Cell/Work)
1 Jo 20 123
2 Sam 25 133
3 Bill 30 170
4 Rick 30 152
5 Rick 30 145
Because Bill is added the new comparison result will say that Rows 4,5 have changed when they actually didn't.
Thanks.
回答1:
I'm guessing that your 'rows' are objects representing rows in an excel table and that you have mapped them as ValueObjects and put them into some list.
Since ValueObjects don't have its own identity, it's unclear, even for a human, what was the actual change. Take a look at your row 4:
Row Name Age Phone(Cell/Work)
before:
4 Rick 30 145
after:
4 Rick 30 152
Did you changed Phone at row 4 from 145 to 152? Or maybe you inserted a new data to row 4? How can we know? We can't. By default, JaVers chooses the simplest answer, so reports value change at index 4.
If you don't care aboute the indices, you can change the list comparision algorithm from Simple to Levenshtein distance. See https://javers.org/documentation/diff-configuration/#list-algorithms
SIMPLE algorithm generates changes for shifted elements (in case when elements are inserted or removed in the middle of a list). On the contrary, Levenshtein algorithm calculates short and clear change list even in case when elements are shifted. It doesn’t care about index changes for shifted elements.
But, I'm not sure if Levenshtein is implemented for ValueObjects, if it is not implemented yet, it's a feature request to javers-core.
来源：https://stackoverflow.com/questions/45194674/why-doesnt-javers-report-the-correct-rows-that-was-added-when-comparing-two-o