如何重用/重置ZipInputStream？

Question

我想重置ZipInputStream (即回到开始位置)，以便按顺序读取某些文件。我该怎么做？我被困住了..。

      ZipEntry entry;
        ZipInputStream input = new ZipInputStream(fileStream);//item.getInputStream());

        int check =0;
        while(check!=2){

          entry = input.getNextEntry();
          if(entry.getName().toString().equals("newFile.csv")){
              check =1;
              InputStreamReader inputStreamReader = new InputStreamReader(input);
                reader = new CSVReader(inputStreamReader);
                //read files
                //reset ZipInputStream if file is read.
                }
                reader.close();
          }
            if(entry.getName().toString().equals("anotherFile.csv")){
              check =2;
              InputStreamReader inputStreamReader = new InputStreamReader(input);
                reader = new CSVReader(inputStreamReader);
                //read files
                //reset ZipInputStream if file is read.
                }
                reader.close();
          }

        }

Answer 1

如果可能(即您有一个实际的文件，而不仅仅是一个要读取的流)，请尝试使用ZipFile类，而不是更低级的ZipInputStream。ZipFile负责在文件中跳来跳去，并向各个条目打开流。

ZipFile zip = new ZipFile(filename);
ZipEntry entry = zip.getEntry("newfile.csv");
if (entry != null){
    CSVReader data = new CSVReader(new InputStreamReader(
         zip.getInputStream(entry)));
} 

Answer 2

实际上没有办法像你期望的那样重置一个ZipInputStream，因为它不支持重置/标记等。但是你可以使用一个ByteArrayOutputStream来缓冲你的InputStream作为byte[]

所以你写一个类，看起来像这样

private byte[] readStreamBuffer;
private InputStream readStream;

public ZipClass(InputStream readStream){
   this.readStream = readStream;
}

和一个像这样的openReadStream-method：

private ZipInputStream openReadStream(){
    if (readStreamBuffer == null) {
         //If there was no buffered data yet it will do some new
         ByteArrayOutputStream readStreamBufferStream = new ByteArrayOutputStream();
         try {
            int read = 0;
            byte[] buff = new byte[1024];
            while ((read = zipFileInput.read(buff)) != -1) {
               readStreamBufferStream.write(buff, 0, read);
            }
            readStreamBuffer = readStreamBufferStream.toByteArray();
         }
         finally {
            readStreamBufferStream.flush();
            readStreamBufferStream.close();
         }
      }
   //Read from you new buffered stream data
   readStream = new ByteArrayInputStream(readStreamBuffer);

   //open new ZipInputStream
   return new ZipInputStream(readStream);
}

现在，您可以读取条目，然后将其关闭。如果您调用openReadStream，它将为您提供一个新的ZipInputStream，因此您可以像这样选择性地读取条目：

public InputStream read(String entry){
  ZipInputStream unzipStream = openReadStream();
  try {
     return readZipEntry(unzipStream, entryName);
  }
  finally {
     unzipStream.close(); //This closes the zipinputstream
  }
}

调用方法readZipEntry

private InputStream readZipEntry(ZipInputStream zis, String entry) throws IOException {
  ByteArrayOutputStream out = new ByteArrayOutputStream();
  try {
     // get the zipped file list entry
     try {
        ZipEntry ze = zis.getNextEntry();

        while (ze != null) {
           if (!ze.isDirectory() && ze.getName().equals(entry)) {
              int len;
              byte[] buffer = new byte[BUFFER];
              while ((len = zis.read(buffer)) > 0) {
                 out.write(buffer, 0, len);
              }
              break;
           }
           ze = zis.getNextEntry();
        }
     }
     finally {
        zis.closeEntry();
     }
     InputStream is = new ByteArrayInputStream(out.toByteArray());
     return is;
  }
  finally {
     out.close();
  }
}

你会得到一个新的InputStream。现在，您可以从同一个输入中多次读取。

Answer 3

您可以将标记包装在BufferedInputStream中，然后调用InputStream ()和reset()方法，如下所示：

BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
bufferedInputStream.mark(100);
ZipInputStream zipInputStream = new ZipInputStream(bufferedInputStream);

    any operation with zipInputStream ...

bufferedInputStream.reset();

传递给readLimit方法的标记必须足够大，以覆盖使用inputStream执行的所有读取操作。如果您将其设置为您在输入中可以拥有的最大假定文件大小，那么您应该会被覆盖。