从ZipInputStream获取特定文件 [英] Getting specific file from ZipInputStream

问题描述

我可以遍历ZipInputStream，但是在开始迭代之前，我想获取迭代期间需要的特定文件.我该怎么办?

I can go through ZipInputStream, but before starting the iteration I want to get a specific file that I need during the iteration. How can I do that?

ZipInputStream zin = new ZipInputStream(myInputStream)
while ((entry = zin.getNextEntry()) != null)
 {
    println entry.getName()
}

推荐答案

如果要使用的myInputStream来自磁盘上的真实文件，则可以简单地使用java.util.zip.ZipFile，它由RandomAccessFile，并按名称提供对zip条目的直接访问.但是，如果您仅有的是InputStream(例如，如果您是直接从网络套接字或类似设备收到来的，就在处理流)，那么您就必须自己进行缓冲.

If the myInputStream you're working with comes from a real file on disk then you can simply use java.util.zip.ZipFile instead, which is backed by a RandomAccessFile and provides direct access to the zip entries by name. But if all you have is an InputStream (e.g. if you're processing the stream directly on receipt from a network socket or similar) then you'll have to do your own buffering.

您可以将流复制到一个临时文件，然后使用ZipFile打开该文件，或者如果您事先知道数据的最大大小(例如，对于预先声明其Content-Length的HTTP请求)，则可以可以使用BufferedInputStream将其缓冲在内存中，直到找到所需的条目为止.

You could copy the stream to a temporary file, then open that file using ZipFile, or if you know the maximum size of the data in advance (e.g. for an HTTP request that declares its Content-Length up front) you could use a BufferedInputStream to buffer it in memory until you've found the required entry.

BufferedInputStream bufIn = new BufferedInputStream(myInputStream);
bufIn.mark(contentLength);
ZipInputStream zipIn = new ZipInputStream(bufIn);
boolean foundSpecial = false;
while ((entry = zin.getNextEntry()) != null) {
  if("special.txt".equals(entry.getName())) {
    // do whatever you need with the special entry
    foundSpecial = true;
    break;
  }
}

if(foundSpecial) {
  // rewind
  bufIn.reset();
  zipIn = new ZipInputStream(bufIn);
  // ....
}

(我还没有亲自测试过这段代码，您可能会发现有必要在bufIn和第一个zipIn之间使用commons-io CloseShieldInputStream之类的东西来关闭第一个zip流.在倒回之前不关闭基础bufIn).

(I haven't tested this code myself, you may find it's necessary to use something like the commons-io CloseShieldInputStream in between the bufIn and the first zipIn, to allow the first zip stream to close without closing the underlying bufIn before you've rewound it).

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