如何在java中获得对象的两个数组列表的差异

Question

我有一个员工列表，一些方法是添加/删除员工或编辑员工的属性

employee{id, name, age, grp}

其中id是标识符

我正在尝试按照以下格式获取旧列表和修改列表之间的所有差异：

我尝试了ObjectDifferBuilder，这是github（https://github.com/SQiShER/java-object-diff）的一个java工具，如下所示：

//actionDataList - Action list for printing the diffs at the end of process
DiffNode diff = ObjectDifferBuilder.buildDefault().compare(newList, oldList);

diff.visit(new DiffNode.Visitor() {
    @Override
    public void node(DiffNode node, Visit visit) {
        String fieldName = "emp.";

        if (node.hasChanges() && !node.hasChildren()) {
            node.canonicalSet(newAe, node.canonicalGet(newAe) + "*");
        }

        if (!(node.getPath() == null || node.getPath().getLastElementSelector().toHumanReadableString().isEmpty())) {
            fieldName += node.getPath().getLastElementSelector().toHumanReadableString();

            Object baseValue = node.canonicalGet(oldList);
            Object workingValue = node.canonicalGet(newList);

            if (baseValue == null && workingValue instanceof String) {
                //for new values inserted
                actionDataList.add(new ActionData(fieldName, "", String.valueOf(workingValue)));
            } else if (workingValue == null && baseValue instanceof String) {                   
                // for old values deleted
                actionDataList.add(new ActionData(fieldName, String.valueOf(baseValue), ""));
            }
        }
    }
});

但仍然没有得到适当的输出

Answer 1

在这里，我做了如下的变通方法。希望这对别人有帮助。（参考代码中的注释）

Map<String, Employee> entityById = 
oldList.stream().collect(Collectors.toMap(Employee::getId, 
Function.identity())); //changed oldList to Map

  for (Employee entity : newList) //iterate new list to check the old values
  {
     if (entityById.containsKey(entity.getId())) // check for updated record
     {
        printActionRecord(entityById.get(entity.getId()), entity, actionDataList,"UPDATED");
        entityById.remove(entity.getId());
     }
     else // check for newly inserted record
     {
        printActionRecord(entityById.get(entity.getId()), entity, actionDataList,"INSERTED");
     }
  }
  if (!entityById.isEmpty()) // check for deleted record from new list( but existing in oldlist)
  {
     entityById.forEach((key, entity) -> {
        printActionRecord(entityById.get(entity.getId()), entity, actionDataList,"DELETED");
     });
  }

在上面，我可以计算出新列表中更新/创建/删除的记录。在我找到这个之后，我将把那个记录和旧记录一起传递（仅在更新的情况下）以获得差异。通过DiffNode diff = ObjectDifferBuilder.buildDefault().compare(newobj, oldobj);它为字段中的每个更改提供了记录

//actionDataList - Action list for printing the diffs at the end of process
DiffNode diff = ObjectDifferBuilder.buildDefault().compare(newObject, oldObject);

diff.visit(new DiffNode.Visitor() {
@Override
public void node(DiffNode node, Visit visit) {
    String fieldName = "emp."; //it should be a variable for each type of field
    if (!(node.getPath() == null || node.getPath().getLastElementSelector().toHumanReadableString().isEmpty())) {
        fieldName += node.getPath().getLastElementSelector().toHumanReadableString();

        Object baseValue = node.canonicalGet(oldObject);
        Object workingValue = node.canonicalGet(newObject);

        if (baseValue == null && workingValue instanceof String) {
            //for new values inserted
            actionDataList.add(new ActionData(fieldName, "", String.valueOf(workingValue)));
        } else if (workingValue == null && baseValue instanceof String) {                   
            // for old values deleted
            actionDataList.add(new ActionData(fieldName, String.valueOf(baseValue), ""));
        } else { // print updates
            actionDataList.add(new ActionData(fieldName, String.valueOf(baseValue), String.valueOf(workingValue))); 
        }
    }
}
});

然后，我们可以打印actionDataList值

for(ActionData a: actionDataList){
    System.out.println("Field:"+ a.getFieldName()+ " Old Value:"+a.getOldValue()+"  NewValue:"+a.getNewValue());
}

希望这有帮助