DELETE and GET have faulty behavior in a Jax-RS Restful App - rest

Question

I am learning how to implement Rest API through a tutorial project.
I am facing a rather strange behavior from a routine I perform in order to test the standard CRUD methods...
Here's a general description of the code architecture:
I am using a stub to emulate a database behavior using a static class which contains a HashMap<Long, Message> with Message being the entity I am manipulating,
This stub hashmap reference is in turn given to a class MessageService which does the logic of the CRUD method implementations,
The MessageService is instanciated in a class MessageRessource which is the Rest API containing all the #GET, #POST, etc... method implementations which call the MessageService instance methods.
I should point out that I added 2 hardcoded entries of Messages in the MessageService constructor which I put in the database stub HashMap
Now, here's the routine which leaves me confused:
Run app,
Do a GET on /messages: Shows 2 entries,
Do a POST with custom data: Data is added,
Do a GET on /messages: Shows 3 entries,
Do a DELETE on /messages/3: Deletes 3rd entry,
Do a GET on /messages: Shows 2 entries,
Do a DELETE on /messages/2: While debugging the app, the
messageService instance in MessageRessource has a hashmap of size 1 after the DELETE method is processed,
Do a GET on /messages: Shows 2 entries instead of 1.
My own thoughts on the problem:
If the constructor which contains the hardcoded data was the cause of
the problem, the GET method in step 4 shouldn't show 3 entries but
only 2.
Perhaps this has to do with the fact that no data is being returned
by the DELETE while the POST does return the added data?
For the code, please see the GitHub public project in the messenger App by AetosAkrivis
N.B : I know this isn't a real problem because I only need to remove the hardcoded Message entries in the constructor in order to be able to perform normally. But I am really curious about the reason of the malfunctioning of this routine.

Answer 1

You have assumed that the JAX-RS container will only create one instance of the service MessageRessource, but it can decide to clean instances or create multiple. Each time it is done the initialization, your static messages will be updated with 2 additional entries. Results are indeterminate
#Path("/messages")
#Consumes(MediaType.APPLICATION_JSON)
#Produces(MediaType.APPLICATION_JSON)
public class MessageRessource {
private MessageService messageService;
public MessageRessource() {
messageService = new MessageService();
}
public MessageService() {
messages.put(1L, new Message(1L,"Hi","Imad"));
messages.put(2L, new Message(2L,"Hello","Badr"));
}
P.S: Post your code instead of linking it