LINQ for Java工具 [英] LINQ for Java tool
问题描述
LINQ for java会成为一个有用的工具吗？我一直在研究一种允许Java对象映射到数据库中的行的工具。
Would a LINQ for java be a useful tool? I have been working on a tool that will allow a Java object to map to a row in a database.
- 这对Java
程序员有用吗？ -
有什么功能？
推荐答案
LINQ for Java会很可爱，但问题在于语言集成。
LINQ for Java would be lovely, but the problem is the language integration.
Java没有像lambda表达式那样简洁的东西，它们是LINQ的基石之一。我认为他们可以在没有lambda表达式的普通Java之上对查询表达式支持进行分层，通过使扩展创建匿名内部类 - 但它会非常可怕。如果你想做LINQ to SQL这样的事情，你还需要表达式树。
Java doesn't have anything as concise as lambda expressions, and they're one of the bedrocks of LINQ. I suppose they could layer the query expression support on top of normal Java without lambda expressions, by making the expansion create anonymous inner classes - but it would be pretty hideous. You'd also need expression trees if you wanted to do anything like LINQ to SQL.
检查异常可能会阻碍，但我们我必须看到。 IQueryable的等价物需要具有某种一般的检查异常 - 或者它可能在元素类型和异常类型中都是通用的......
Checked exceptions might get in the way, but we'd have to see. The equivalent of IQueryable would need to have some sort of general checked exception - or possibly it could be generic in both the element type and the exception type...
无论如何，这是天上掉馅饼 - 考虑到Java社区关闭的麻烦，我认为在2012年之前预期像Java中的LINQ这样的东西是愚蠢的。当然，这并不是说它不会用类似Java的语言是可能的。例如，Groovy已经有了一些有用的方面。
Anyway, this is all pie-in-the-sky - given the troubles the Java community is having with closures, I think it would be folly to expect anything like LINQ in Java itself earlier than about 2012. Of course, that's not to say it wouldn't be possible in a "Java-like" language. Groovy has certain useful aspects already, for instance.
对于库方面，Hibernate已经提供了LINQ to SQL的许多功能的非集成版本。对于LINQ to Objects，您应该查看 Google Java Collections API - 这是很多相同类型的事物（过滤，投射等）。当然，如果没有lambdas，它的使用时间会非常繁琐 - 但它仍然非常非常方便。 （我在工作中一直使用Google Collections代码，我不想回到vanillaJava集合。）
For the library side, Hibernate already provides a "non-integrated" version of a lot of the features of LINQ to SQL. For LINQ to Objects, you should look at the Google Java Collections API - it's a lot of the same kind of thing (filtering, projecting etc). Without lambdas it's a lot fiddlier to use, of course - but it's still really, really handy. (I use the Google Collections code all the time at work, and I'd hate to go back to the "vanilla" Java collections.)
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