Java，将（转换）可序列化对象转换为其他对象

Question

I'm using Session.save() method (in Hibernate) to persist my entity objects which returns an object of type java.io.Serializable .

The returned value is the generated primary key for the entity.

The generated primary key is of type long (or bigint).

The question is that: How can I convert or cast the returned value to long ?

Serializable result = session.save(myEntityObject);

//This line of code fails. 
long r = (long)result;

Answer 1

Try casting the result (since it's not a primitive) to Long instead of long .

Long r = (Long)result;
long longValue = r.longValue();

Answer 2

尝试

long r = Long.valueOf(String.valueOf(result)).longValue();

Answer 3

Have you tried using a debugger and breaking at that line to see what "result" is exactly?

It could be BigDecimal or Long or ...

Alternatively, cant you just call the primary key getter method on the object - I'd have hoped it would be set by that point.

HTH, Chris

Answer 4

Above answer not worked for me.

I misunderstood the function of statelessSession.get(...) . The second parameter should be the primitive value of the primary-key if it is a non-composte key.

If the Entity has a composite key you should pass the entity itself (with filled pk) as second argument.

I was confused, because I thought that I need to pass always an entity as second argument to statelessSession.get (because it works for multi-key-entitys).

Answer 5

尝试使用long r = ((Long) result).getLong()代替。

Answer 6

You should have specified the type of error you are getting ! Anyways this should work..

long r = Long.valueOf(result)