Scala 中的数据压缩 [英] Data compression in Scala

问题描述

下面是我尝试实现一个提供压缩/解压缩字符串功能的类:

Here below is my attempt to implement a class that provides functionality for compressing/decompressing strings:

object GZipHelper {

  def deflate(txt: String): Try[String] = {
    try {
      val arrOutputStream = new ByteArrayOutputStream()
      val zipOutputStream = new GZIPOutputStream(arrOutputStream)
      zipOutputStream.write(txt.getBytes)
      new Success(Base64.encodeBase64String(arrOutputStream.toByteArray))
    } catch {
      case _: e => new Failure(e)
    }
  }

  def inflate(deflatedTxt: String): Try[String] = {
    try {
      val bytes = Base64.decodedBase64(deflatedTxt)
      val zipInputStream = GZIPInputStream(new ByteArrayInputStream(bytes))
      new success(IOUtils.toString(zipInputStream))
    } catch {
      case _: e => new Failure(e)
    }
  }
}

如您所见，关闭 GZIPOutputStream 和 GZIPInputStream 的 finally 块丢失了......我怎么能在''scala' 方式?我该如何改进代码?

As you can see, the finally blocks that close GZIPOutputStream and GZIPInputStream are missing... how could I implement this in the ''scala'' way? How could I improve the code?

推荐答案

由于您使用的是老式"try 语句并将其显式转换为 scala.util.Try，真的没有理由不在你的 try 之后添加一个 finally 块.

Since you're using the "old fashioned" try statement and explicitly turning it into a scala.util.Try, there really is no reason not to add a finally block after your try.

不过，在这种特定情况下，关闭没有什么意义，例如，您的 ByteArrayInputStream - 它不是真正的开放资源，不需要关闭.在这种情况下，您可以通过这种方式简化代码并使其更加地道:

In this specific case though, there is little point in closing, for example, your ByteArrayInputStream - it's not really an open resource and does not need to be closed. In which case you can simplify your code and make it much more idiomatic this way:

def inflate(deflatedTxt: String): Try[String] = Try {
   val bytes = Base64.decodedBase64(deflatedTxt)
   val zipInputStream = GZIPInputStream(new ByteArrayInputStream(bytes))
   IOUtils.toString(zipInputStream)
}

我个人不会声明 bytes 和 zipInputStream 因为它们只使用一次，但这是一个偏好问题.

I personally would not declare bytes and zipInputStream since they're only used once, but that's a matter of preference.

这里的技巧是使用 finally 块调用 scala.util.Try.apply - 我不确定不通过调用map 实际上并没有修改任何东西，这对我来说似乎有点疏忽.我期待在 scala.util.Try 中看到 andThen 或 eventually 方法，但它似乎不存在(还没有?).

The trick here is having a finally block with a call to scala.util.Try.apply - I'm not sure that's possible without going through a call to map that doesn't actually modify anything, which seems like a bit of an oversight to me. I was expecting to see an andThen or eventually method in scala.util.Try, but it doesn't seem to be there (yet?).

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