To reduce code duplication for every update of an attribute in JPA, I'd like to hand over a function pointer to doTransaction and invoke the function. How can I do that in Java 8?
public void modifySalary(Person person, float salary) {
doTransaction(person.setSalary(salary));
}
public void doTransaction(final Function<Void, Void> func) {
em.getTransaction().begin();
func.apply(null);
em.getTransaction().commit();
}
You could accept a Runnable as argument of doTransaction and pass it a lambda expression updating the person. Here, we are only using Runnable as a functional interface that defines a method taking no parameters and returning no value.
public void modifySalary(Person person, float salary) {
doTransaction(() -> person.setSalary(salary));
}
public void doTransaction(Runnable action) {
em.getTransaction().begin();
action.run();
em.getTransaction().commit();
}
If you think the name Runnable is somehow too linked to threads, you could roll your own interface defining a functional method taking no parameters and returning no value. For example, if you want to name it Action, you could have
@FunctionalInterface
interface Action {
void perform();
}
and then call action.perform() inside doTransaction.
Runnable isn’t linked to threads. The API designers deliberately decided not to include a void noarg function in the java.util.function package because the already existing type Runnable fulfills this requirement.In this case you need a parameterless void function, a Runnable would be sufficient.
public void modifySalary(Person person, float salary) {
doTransaction(()->person.setSalary(salary));
}
public void doTransaction(Ruunable runnable) {
em.getTransaction().begin();
runnable.run();
em.getTransaction().commit();
}
