Concurrency saving

Hello, everyone!

I tried to implement concurrency saving in the GWT 2.4.

There is a user case:

1. Users John and Jim open one entity to editing

2. John saves his changes. All is OK.

3. Jim saves his changes. System asked about overwrite

   a. Jim does not want to overwrite, system just refreshes entity at the page

   b. Otherwise, if Jim wants to save his changes, changes must be persisted and John's changes will be destroyed. (left only in the history of changes)

So I have problem with 3.b.

public void save(MyEntityProxy entity){

   MyRequest rContext = (MyRequest) driver.flush();

  MyProxy myEntity = (MyProxy) rContext.edit(entity);

  entitySave(rContext, (MyProxy) myEntity, false);

}

private void entitySave(MyRequest rContext, final MyProxy myEntity, boolean overwrite){

  GWT.log("SAVE ENTITY WITH NAME = " + myEntity.getName());

  rContext.persist(myEntity, entityVersion, overwrite).fire(new Receiver<MyProxy>() {

    @Override

    public void onSuccess(MyProxy response) {

       goToList();

    }

    @Override

    public void onFailure(ServerFailure error) {

      if(isConcurency(error)){

        entitySave((MyRequest)getNewRequestContext(), myEntity,true);

      }

   }

  });

}

/*This is a method from MyService for persisting*/

public MyProxy persist(MyProxy entity, Long version, boolean overwrite) {

   LOG.info("PERSISTS ENTITY NAME=" + entity.getName());

   if(!overwrite && !checkVersionChanged(entity, version)){ System.out.println("RAISE CHANGED_BY_OTHER EXCEPTION");

     throw new RuntimeException(ServerFailureCode.CHANGED_BY_OTHER.name());

   }

   entity = getEntityManager().merge(entity);

   getEntityManager().flush();

   return entity;

}

isConcurrency is a method for checking concurrency issue and returns true when user choose "overwrite" point in the dialog.

GWT log:

SAVE ENTITY WITH NAME = John //There is John changed name of entity

SAVE ENTITY WITH NAME = Jim //There is John changed name of entity

SAVE ENTITY WITH NAME = Jim //There is John overwrites entity

Server Log:

[INFO] PERSISTS ENTITY NAME=John        //There is John changed name of entity

[INFO] SAVE ENTITY NAME=John            //Persisting of John's changes. John finished his work

[INFO] PERSISTS ENTITY NAME=Jim         //There is Jim changed name of entity

[INFO] RAISE CHANGED_BY_OTHER EXCEPTION //Exception raises and dialog shows for Jim

[INFO] PERSISTS ENTITY NAME=John        //Second iteration of saving. Look at the name!.

I do not understand what happened. When Jim overwrites his changes, at the client layer all is correct, but server layer works with data saved by previous user.

Is anybody knows how can I correctly overwrite changes in this situation?

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