休眠保存数据（如果数据库中不存在），否则对其进行更新

Question

I am relatively new to hibernate and looking for any mechanism where I insert new record only if the composite key is not present and else update it.

I tried with saveOrUpdate method but seems it only works for the objects in the session. I want some mechanism which should query at database and if the data is present in the database already then update the record else insert it.

Thanks,

Amandeep

Answer 1

As mentioned in the hibernate docs,saveOrUpdate() method should satisfy your requirement. Hibernate Session doc

void saveOrUpdate(Object object) throws HibernateException Either save(Object) or update(Object) the given instance, depending upon resolution of the unsaved-value checks (see the manual for discussion of unsaved-value checking). This operation cascades to associated instances if the association is mapped with cascade="save-update".

Parameters: object - a transient or detached instance containing new or updated state

Posting a sample code for your reference: In the below method a Stock object is newly inserted into the database.

Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();

        Stock stock = new Stock();
        stock.setStockId(70);
        stock.setStockCode("7052");
        stock.setStockName("TEST SAVE");

        StockRecord stockRecords = new StockRecord();
        stockyRecords.setDaily_record_id(80);
        stockRecords.setPriceOpen(new Float("1.2"));
        stockRecords.setPriceClose(new Float("1.1"));
        stockRecords.setPriceChange(new Float("10.0"));  

        stockRecords.setStock(stock);        
        stock.getStockRecords().add(stockRecords);

        session.save(stock);
        session.save(stockRecords);

        session.getTransaction().commit();
        session.close();

Then in another method you open a new Session and then try to insert or update a Stock object(StockId is the primary key,if you give the same id,it will update and if you give a new id,it will insert,here i have retained it as 70)

public static void testSaveOrUpdate(){      
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.beginTransaction();
        Stock stock = new Stock();
        stock.setStockId(70);
        stock.setStockCode("7052");
        stock.setStockName("Test SaveOrUpdate");

        StockRecord stockRecords = new StockRecord();
        stockRecords.setDaily_record_id(90);
        stockRecords.setPriceOpen(new Float("1.3"));
        stockRecords.setPriceClose(new Float("1.1"));
        stockRecords.setPriceChange(new Float("10.0"));

        stockRecords.setStock(stock);        
        stock.getStockRecords().add(stockRecords);

        session.saveOrUpdate(stock);        
        session.getTransaction().commit();
    }

Just make sure that if you have a relationship to some other entity(in this case StockRecord) you give the appropriate CASCADE value.In this case,CascaseType is set to ALL.

@OneToMany(cascade = CascadeType.ALL, orphanRemoval = false)
    @JoinColumn(name = "stockId", updatable = true, insertable = true)
    private Set<StockRecord> stockRecords = 
                            new HashSet<StockRecord>(0);