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Using Optionals correctly in service layer of spring boot application

I new to spring boot application development. I using service layer in my application, but came across the repository method that return Optional as shown below.
#Override
public Questionnaire getQuestionnaireById(Long questionnaireId) {
Questionnaire returnedQuestionnaire = null;
Optional<Questionnaire> questionnaireOptional = questionnaireRepository.findById(questionnaireId);
if(questionnaireOptional.isPresent()) {
returnedQuestionnaire = questionnaireOptional.get();
}
return returnedQuestionnaire;
}
My question is ,
whether I am using the Optional correctly here. And is it ok to check this optional (isPresent()) in the RestController and throughing exception is not present.Like below
public Optional<Questionnaire> getQuestionnaireById(Long questionnaireId) {
return questionnaireRepository.findById(questionnaireId);
}

I wouldn't go for either option tbh, especially not the first. You don't want to introduce null values inside your domain. Your domain should stay as simple as possible, readable and void of clutter like null checks.
You might want to read through the optional API for all your options, but personally I would go for something like this:
In repository:
public interface TodoBoardRepository {
Optional<Questionnaire> findByQuestionnaireId(String questionnaireId);
// ...
}
In service:
#Service
#RequiredArgsConstructor // Or generate constructor if you're not using Lombok
public class QuestionnaireService {
private final QuestionnaireRepository questionnaireRepository;
// ...
public Questionnaire getQuestionnaireById(Long questionnaireId) {
Questionnaire questionnaire = questionnaireRepository.findById(questionnaireId)
.orElseThrow(() -> new QuestionaireNotFoundException(questionnaireId));
// Do whatever you want to do with the Questionnaire...
return questionnaire;
}
}

I go with way 1 that you have mentioned. In case the object is not present, throw a validation exception or something. This approach also ensures that service layer is in charge of the logic and controller is just used your interacting with the outside world.

Spring Data Rest: Limit sending values on Update method

I have implemented by project using Spring-Data-Rest. I am trying to do an update on an existing record in a table. But when I try to send only a few fields instead of all the fields(present in Entity class) through my request, Spring-Data-Rest thinking I am sending null/empty values. Finally when I go and see the database the fields which I am not sending through my request are overridden with null/empty values. So my understanding is that even though I am not sending these values, spring data rest sees them in the Entity class and sending these values as null/empty. My question here is, is there a way to disable the fields when doing UPDATE that I am not sending through the request. Appreciate you are any help.
Update: I was using PUT method. After reading the comments, I changed it to PATCH and its working perfectly now. Appreciate all the help

Before update, load object from database, using jpa method findById return object call target.
Then copy all fields that not null/empty from object-want-to-update to target, finally save the target object.
This is code example:
public void update(Object objectWantToUpdate) {
Object target = repository.findById(objectWantToUpdate.getId());
copyNonNullProperties(objectWantToUpdate, target);
repository.save(target);
}
public void copyNonNullProperties(Object source, Object target) {
BeanUtils.copyProperties(source, target, getNullPropertyNames(source));
}
public String[] getNullPropertyNames (Object source) {
final BeanWrapper src = new BeanWrapperImpl(source);
PropertyDescriptor[] propDesList = src.getPropertyDescriptors();
Set<String> emptyNames = new HashSet<String>();
for(PropertyDescriptor propDesc : propDesList) {
Object srcValue = src.getPropertyValue(propDesc.getName());
if (srcValue == null) {
emptyNames.add(propDesc.getName());
}
}
String[] result = new String[emptyNames.size()];
return emptyNames.toArray(result);
}

You can write custom update query which updates only particular fields:
#Override
public void saveManager(Manager manager) {
Query query = sessionFactory.getCurrentSession().createQuery("update Manager set username = :username, password = :password where id = :id");
query.setParameter("username", manager.getUsername());
query.setParameter("password", manager.getPassword());
query.setParameter("id", manager.getId());
query.executeUpdate();
}

As some of the comments pointed out using PATCH instead of PUT resolved the issue. Appreciate all the inputs. The following is from Spring Data Rest Documentation:
"The PUT method replaces the state of the target resource with the supplied request body.
The PATCH method is similar to the PUT method but partially updates the resources state."
https://docs.spring.io/spring-data/rest/docs/current/reference/html/#customizing-sdr.hiding-repository-crud-methods
Also, I like #Tran Quoc Vu answer but not implementing it for now since I dont have to use custom controller. If there is some logic(ex: validation) involved when updating the entity, I am in favor of using the custom controller.

How can I "patch" a JPA entity?

Let's pretend a RESTful service receives a PATCH request to update one or more fields of an entity that might have tens of fields.
#Entity
public class SomeEntity {
#Id
#GeneratedValue
private Long id;
// many other fields
}
One dirty way to patch the corresponding entity is to write something like this:
SomeEntity patch = deserialize(json);
SomeEntity existing = findById(patch.getId());
if (existing != null)
{
if (patch.getField1() != null)
{
existing.setField1(patch.getField1());
}
if (patch.getField2() != null)
{
existing.setField2(patch.getField2());
}
if (patch.getField3() != null)
{
existing.setField3(patch.getField3());
}
}
But this is insane! And if I want to patch 1 to many & other associations of the entity the insanity could even become hazardous!
Is there a sane an elegant way to achieve this task?

Modify the getter's of SomeEntity and apply check, if any value is blank or null just return the corresponding entity object value.
class SomeEntity {
transient SomeEntity existing;
private String name;
public String getName(){
if((name!=null&&name.length()>0)||existing==null){
return name;
}
return existing.getName();
}
}

You can send an array containing the name of the fields you are going to patch. Then, in the server side, by reflection or any field mapping, set each field to the entity. I have already implemented that and it works, thought my best advice is this:
Don't publish an endpoint to perform a "generic" PATCH (modification), but one that performs a specific operation. For instance, if you want to modify an employee's address, publish an endpoint like:
PUT /employees/3/move
that expects a JSON with the new address {"address" : "new address"}.

Instead of reinventing the wheel by writing the logic yourself, why don't you use a mapping library like Dozer? You want to use the 'map-null' mapping property: http://dozer.sourceforge.net/documentation/exclude.html
EDIT I am not sure whether or not it would be possible to map a class onto itself. You could use an intermediary DTO, though.

Force ebean to update the object

I have a Play Framework 2 application
I use play 2.2.2 built with Scala 2.10.3 (running Java 1.7.0_25).
I have a method that checks the object with his copy from secured table. If the object has been changed it will be replaced with the object from secured table.
But when I call save ebean does not update it:
[debug] c.a.e.s.p.DefaultPersister - Update skipped as bean is unchanged
public static <T> T findAndRestore(Class<T> clazz, Long id) throws Exception {
T securedObject = SecuredEntityUtils.getObjectFromSecuredTable(clazz, id);
T entity = Ebean.find(clazz, id);
if (securedObject != null) {
if (entity == null) {
Ebean.save(securedObject);
} else if (!entity.equals(securedObject)) {
Ebean.update(securedObject);
}
} else {
logger.warn("Not found securedObject for entity : " + entity.getClass());
}
return securedObject ;
}
Is there a way to force ebean to save/update entire object ?

I might be wrong but Ebean did not mark the entity as dirty since you did not called any setter on it. Maybe using Ebean.markAsDirty(entity) could solve your issue (I know this is a pretty old question but since I stumbled upon it, maybe my answer could help somebody)

How to refresh an entity in a Future?

I am not really sure where my problem lies, as I am experimenting in two areas that I don't have much experience with: JPA and Futures (using Play! Framework's Jobs and Promises).
I have the following bit of code, which I want to return a Meeting object, when one of the fields of this object has been given a value, by another thread from another HTTP request. Here is what I have:
Promise<Meeting> meetingPromise = new Job<Meeting> () {
#Override
public Meeting doJobWithResult() throws Exception {
Meeting meeting = Meeting.findById(id);
while (meeting.bbbMeetingId == null) {
Thread.sleep(1000);
meeting = meeting.refresh(); // I tried each of these
meeting = meeting.merge(); // lines but to no avail; I
meeting = Meeting.findById(id); // get the same result
}
return meeting;
}
}.now();
Meeting meeting = await(meetingPromise);
As I note in the comments, there are three lines in there, any one of which I think should allow me to refresh the contents of my object from the database. From the debugger, it seems that the many-to-one relationships are refreshed by these calls, but the single values are not.
My Meeting object extends Play! Framework's Model, and for convenience, here is the refresh method:
/**
* Refresh the entity state.
*/
public <T extends JPABase> T refresh() {
em().refresh(this);
return (T) this;
}
and the merge method:
/**
* Merge this object to obtain a managed entity (usefull when the object comes from the Cache).
*/
public <T extends JPABase> T merge() {
return (T) em().merge(this);
}
So, how can I refresh my model from the database?

So, I ended up cross-posting this question on the play-framework group, and I got an answer there. So, for the discussion, check out that thread.
In the interest of having the answer come up in a web search to anyone who has this problem in the future, here is what the code snippet that I pasted earlier looks like:
Promise<Meeting> meetingPromise = new Job<Meeting> () {
#Override
public Meeting doJobWithResult() throws Exception {
Meeting meeting = Meeting.findById(id);
while (meeting.bbbMeetingId == null) {
Thread.sleep(1000);
if (JPA.isInsideTransaction()) {
JPAPlugin.closeTx(false);
}
JPAPlugin.startTx(true);
meeting = Meeting.findById(id);
JPAPlugin.closeTx(false);
}
return meeting;
}
}.now();
Meeting meeting = await(meetingPromise);
I am not using the #NoTransaction annotation, because that messes up some other code that checks if the request is coming from a valid user.

I'm not sure about it but JPA transactions are managed automatically by Play in the request/controller context (the JPAPlugin opens a transaction before invocation and closes it after invocation).
But I'm not sure at all what happens within jobs and I don't think transactions are auto-managed (or it's a feature I don't know). So, is your entity attached to an entitymanager or still transient? Is there a transaction somewhere? I don't really know but it may explain some weird behavior if not...