如何同时处理通话请求

Question

I am using Spring boot create a restful for save data to Database. Now I have problem when you call this service in the same time my data its duplicated in database because previous request not finish yet.

I generate number like 00001 I need to running its from database

1. I get last from DB
2. then 00001+1 = 00002
3. save to Database

but when request same time in database save 00002 for 2 records.

     @Transactional
public List<Object> saveData(String data) {
 //validate data
 //Get Last Data    
 //set prepare data
 //save data
    int idLatest = Integer.parseInt(getLatest("7", "8"));
    List<Object> objects = autoGenarateEntity(idLatest);
    Repository.save(Object);

}

   public String getLatest(String idFirst, String idSecond){
    Optional<Object> running = Repository.findByBIdStartingWithOrderByBIdDesc(idFirst, idSecond).stream().findFirst();
    if(running.isPresent()){
        String bId =running.get();
        return bId.getBId();
    }else {
        return "70000000";
    }

}

   public List<Object> autoGenarateEntity(int idLatest){
    List<Object> objects = new ArrayList<>();
    IntStream.range(1, 5 + 1).forEach(i -> {
        Object obj = new Object();
        obj.setBId(Integer.toString(idLatest + i));

        obj.add(Object);
    });
    return objects;
}

Answer 1

Following are the options that can be done in this case:

1.) have unique key constraint for the column having the value of 00001. So that, the second transaction which was trying to commit same value would roll-back. And you could use Spring-Retry mechanism to execute the second transaction with updated value

2.) Use a custom sequence Generator to increment the value, instead of handling it yourself.

Answer 2

I have a solution for this

 @Transactional(isolation = Isolation.SERIALIZABLE)

and use spring retry