Springboot - Weekdays count query - sql

Question

My Use-cases:
We have an installation schedule entity (check below code) and it has an installation date.
Once installation has completed, after 4 weekdays we will verify the installation status with customers.
Note: (4 weekdays - this count is configurable. So 'X' weekdays)
Weekdays means - Monday to Friday. We don't care about other holidays.
I have a scheduler, it will retrieve these orders after 'X' weekdays - I'm stuck here
I don't know how to make a query for after 'X' weekdays.
My code:
#Entity
#Table(schema = "myschema", name = "installation_dates")
#Getter
#Setter
#NoArgsConstructor
public class InstallDates extends TransEntity implements Serializable {
// other columns
#Column(name = "installation_schedule_datetime")
private LocalDateTime installationScheduleDatetime;//I use this column for calculation
#Formula("getWeekDaysCount(installationScheduleDatetime)")
private int weekDaysCount;
public int getWeekDaysCount(LocalDateTime installationScheduleDatetime) {
int totalWeekDays = 0;
LocalDateTime todayDate = LocalDateTime.now();
while (!installationScheduleDatetime.isAfter(todayDate)) {
switch (installationScheduleDatetime.getDayOfWeek()) {
case FRIDAY:
case SATURDAY:
break;
default:
totalWeekDays++;
break;
}
installationScheduleDatetime = installationScheduleDatetime.plusDays(1);
}
return totalWeekDays;
}
}
Question:
How to make a SQL or JPQL or JPA query for weekdays?
I knew its very basic question, I am a mobile app developer, I recently joined the Springboard team, it's really hard for me :(
Feel free to give your valuable feedback!

Answer 1

I have a following suggestion if I correctly got the problem.
Java:
Take the current date
Find the date of interest: count minus 4 workdays (so if it is Friday today - subtract 4 days, if it is Monday - subtract 2 days for weekend and 4 more days for weekdays)
Then write a query that will select all installations that were done on the date of interest.
In pseudo code:
select * from installations where installation_date = <date of interest>;.
Date of interest Java code:
public LocalDateTime getDateOfInterest(int workdays) {
LocalDateTime currentDate = LocalDateTime.now();
if (workdays < 1) {
return currentDate;
}
//it will subtract 'X' working days from current date
LocalDateTime result = currentDate;
int addedDays = 0;
while (addedDays < workdays) {
result = result.minusDays(1);
if (!(result.getDayOfWeek() == DayOfWeek.FRIDAY ||
result.getDayOfWeek() == DayOfWeek.SATURDAY)) {
++addedDays;
}
}
return result;
}

Answer 2

First lets answer your questions
No you cannot call a method from #Formula
You probably could (see here but that might depend on your database.
The fact that you use an entity and JPA doesn't mean everything has to be a JPA property.
You could:
Write a get method that calculates it on the fly
Write a getter which sets it lazily.
Use the #PostLoad to always set it.
#Entity
#Table(schema = "myschema", name = "installation_dates")
#Getter
#Setter
#NoArgsConstructor
public class InstallDates extends TransEntity implements Serializable {
// other columns
#Column(name = "installation_schedule_datetime")
private LocalDateTime installationScheduleDatetime;//I use this column for calculation
public int getWeekDaysCount() {
int totalWeekDays = 0;
LocalDateTime isdt = this.installationScheduleDatetime;
LocalDateTime todayDate = LocalDateTime.now();
while (!isdt.isAfter(todayDate)) {
switch (isdt.getDayOfWeek()) {
case FRIDAY:
case SATURDAY:
break;
default:
totalWeekDays++;
break;
}
isdt = isdt.plusDays(1);
}
return totalWeekDays;
}
}
Or if you really want it to be a property, you could use the getter to set it lazily.
#Entity
#Table(schema = "myschema", name = "installation_dates")
#Getter
#Setter
#NoArgsConstructor
public class InstallDates extends TransEntity implements Serializable {
// other columns
#Column(name = "installation_schedule_datetime")
private LocalDateTime installationScheduleDatetime;//I use this column for calculation
private int weekDaysCount = -1;
public int getWeekDaysCount() {
if (weekDaysCount == -1) {
int totalWeekDays = 0;
LocalDateTime isdt = this.installationScheduleDatetime;
LocalDateTime todayDate = LocalDateTime.now();
while (!isdt.isAfter(todayDate)) {
switch (isdt.getDayOfWeek()) {
case FRIDAY:
case SATURDAY:
break;
default:
totalWeekDays++;
break;
}
isdt = isdt.plusDays(1);
}
weekDaysCount = totalWeekDays;
}
return weekDaysCount;
}
}
Or if you always want to calculate that value you could even place it in an #PostLoad annotation on a method to initialize it (you could even reuse the above lazy getter for it). Or move the init code to the #PostLoad annotated method.
#PostLoad
private void initValues() {
getWeekDaysCount();
}

Answer 3

#Formula specifies an expression written in native SQL that is used to read the value of an attribute instead of storing the value in a Column. (https://docs.jboss.org/hibernate/orm/current/javadocs/org/hibernate/annotations/Formula.html)
As for your case, it doesn't look like there's much use in storing weekDaysCount in the DB if it's derived from installationScheduleDatetime. I'd just mark the weekDaysCount as #Transient and be done with it (#Formula should be removed).
Another solution would be to leave weekDaysCount non-transient and put your calculations in a #PreUpdate/#PrePersist method. See https://www.baeldung.com/jpa-entity-lifecycle-events for more info on that.