How to check if instance entity has been modify in the view? - jsf

Question

I need a guide here.
Let's say that I'm fetching some records from db an I'm populating a ui datatable with those records.
The datatable can modify the values of the records as its columns are inputs.
<p:dataTable value="#{videogames.videogameList}" var="vg" >
<p:column headerText="Name">
<p:inputText value="#{vg.name}" />
</p:column>
</p:dataTable>
How can I know if some row was modify in order to update the value in the database?
Should I check each element in the list and compare it to a temporal arraylist with the original values? Is there a more "elegant" way to do this?
Do you know any tutorial or docs that can help me to learn all this.
Thanks!
I am working with Java, JSF, primafaces and JPA.

Answer 1

I wish I could post it as a comment, but I lack the rep for it. I hope it serves as an answer (since you've asked for sources to learn it).
I work with PrimeFaces as well, but personally I haven't dealt with editable rows yet. Skimming over the links I give below, what you want should be doable with a RowEditEvent.
The PrimeFaces showcase is sort of a tutorial in and of itself. Here is the link for editable datatables:
http://www.primefaces.org/showcase/ui/data/datatable/edit.xhtml
Navigate through the xhtml and .java examples. It should bootstrap you in the right direction.
PrimeFaces documentation is a great source of info as well:
http://www.primefaces.org/docs/guide/primefaces_user_guide_5_3.pdf

Answer 2

There is an Ajax event called rowEdit that should help you. There is complementing event called rowEditCancel to detect when the user backs out of an edit.
The primefaces website offers a user guide that goes into a fair amount of detail for data tables and the rest of the framework. This is the link for the latest version 5.3.
primefaces 5.3 users guide

Answer 3

I think I found a solution for this case.
What I did, was to add an ajax listener with event="change", to the inputtext that can modify the value of the row, so everytime the value changes, the listener will pass the row as a param to a method, and the method will add the row to a list:
videogames.xhtml
<p:column headerText="Nombre">
<p:inputText value="#{vj.nombre}">
<!--this is the added listener-->
**<f:ajax event="change" listener="#{videojuegos.rowSelectedTest(vj)}" />**
</p:inputText>
</p:column>
<!-- **Button that calls the method for updating the modify entities columns**-->
<p:commandButton value="Actualizar" actionListener="#{videojuegos.updateVideojuego()}"/>
The managed bean receives it, and adds it to a list:
VideoGamesManagedBean.java
List <Videojuego> videojuegoUpdate = new ArrayList<Videojuego>();
//adds the modify row to a list
public void rowSelectedTest(Videojuego videojuego){
videojuegoUpdate.add(videojuego);
}
//calls the method in the EJB for merging each object in the list
public void updateVideojuego(){
if(videojuegoUpdate != null && !videojuegoUpdate.isEmpty() ){
vjbean.mergeVideojuegoList(videojuegoUpdate);
//after merging, cleans up the arraylist.
videojuegoUpdate.clear();
}
}
and last, the EJB iterates through the list and merge each object
VideoGameBean.java
#PersistenceContext
private EntityManager em;
public void mergeVideojuegoList(List<Videojuego> listVideojuegoUpdate){
for(Videojuego vjUpdate : listVideojuegoUpdate ){
em.merge(vjUpdate);
}
}
NOTE:
the only "problem" for this is, if I modify several times the same column before I hit the commandbutton "Actualizar", the list will grow up with the same row. But the merge method will take the last "version" of the column. So for our needs, it is ok.
Thanks for the previous answers, regards!!
If you know any better method or find any corner case, let me know!!