Java，将（转换）可序列化对象转换为其他对象
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Java, convert(cast) Serializable objects to other objects
提问by Ali Khoshsirat
I'm using Session.save()method (in Hibernate) to persist my entity objects which returns an object of type java.io.Serializable.
我正在使用Session.save()方法（在 Hibernate 中）来持久化我的实体对象，它返回一个类型为 的对象java.io.Serializable。
The returned value is the generated primary key for the entity.
返回值是为实体生成的主键。
The generated primary key is of type long(or bigint).
生成的主键是类型long（或 bigint）。
The question is that: How can I convert or cast the returned value to long?
问题是：如何将返回的值转换或转换为long？
Serializable result = session.save(myEntityObject);
//This line of code fails.
long r = (long)result;
回答by Bhesh Gurung
Try casting the result (since it's not a primitive) to Longinstead of long.
尝试将结果（因为它不是原始的）转换为Long而不是long.
Long r = (Long)result;
long longValue = r.longValue();
回答by Chris Kimpton
Have you tried using a debugger and breaking at that line to see what "result" is exactly?
您是否尝试过使用调试器并在该行中断以查看“结果”究竟是什么？
It could be BigDecimal or Long or ...
它可以是 BigDecimal 或 Long 或 ...
Alternatively, cant you just call the primary key getter method on the object - I'd have hoped it would be set by that point.
或者，您不能只调用对象上的主键 getter 方法 - 我希望它会在那时设置。
HTH, Chris
HTH，克里斯
回答by James DW
Try
尝试
long r = Long.valueOf(String.valueOf(result)).longValue();
回答by Rakesh
You should have specified the type of error you are getting ! Anyways this should work..
您应该已经指定了您遇到的错误类型！无论如何这应该工作..
long r = Long.valueOf(result)
回答by Xavi López
Try using long r = ((Long) result).getLong()instead.
尝试使用long r = ((Long) result).getLong()。
回答by H-net
thank you for your answers, but they were not the solution...
感谢您的回答，但它们不是解决方案...
I found it out... 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.
我发现了...我误解了 statelessSession.get(...) 的功能。如果是非组合键，第二个参数应该是主键的原始值。
If the Entity has a composite key you should pass the entity itself(with filled pk) as second argument...
如果实体有一个复合键，你应该将实体本身（用填充的 pk）作为第二个参数传递......
i was confused, because i thought that i need to pass allways an entity as second argument to statelessSession.get (because it works for multi-key-entitys)
我很困惑，因为我认为我需要将一个实体作为第二个参数传递给 statelessSession.get（因为它适用于多键实体）
Regards
问候
