Java:如何将InputStream转换为GZIPInputStream? [英] Java: How do I convert InputStream to GZIPInputStream?

问题描述

我有类似的方法

      public void put(@Nonnull final InputStream inputStream, @Nonnull final String uniqueId) throws PersistenceException {
        // a.) create gzip of inputStream
        final GZIPInputStream zipInputStream;
        try {
            zipInputStream = new GZIPInputStream(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
            throw new PersistenceException("Persistence Service could not received input stream to persist for " + uniqueId);
        }

我想将inputStream转换为zipInputStream，该怎么做?

I wan to convert the inputStream into zipInputStream, what is the way to do that?

• 上述方法不正确，并引发异常为非Zip格式"

将Java Streams转换为我真的很混乱，我做错了

converting Java Streams to me are really confusing and I do not make them right

推荐答案

The GZIPInputStream is to be used to decompress an incoming InputStream. To compress an incoming InputStream using GZIP, you basically need to write it to a GZIPOutputStream.

如果使用 ByteArrayOutputStream 将压缩后的内容写入byte[]和

You can get a new InputStream out of it if you use ByteArrayOutputStream to write gzipped content to a byte[] and ByteArrayInputStream to turn a byte[] into an InputStream.

所以，基本上:

public void put(@Nonnull final InputStream inputStream, @Nonnull final String uniqueId) throws PersistenceException {
    final InputStream zipInputStream;
    try {
        ByteArrayOutputStream bytesOutput = new ByteArrayOutputStream();
        GZIPOutputStream gzipOutput = new GZIPOutputStream(bytesOutput);

        try {
            byte[] buffer = new byte[10240];
            for (int length = 0; (length = inputStream.read(buffer)) != -1;) {
                gzipOutput.write(buffer, 0, length);
            }
        } finally {
            try { inputStream.close(); } catch (IOException ignore) {}
            try { gzipOutput.close(); } catch (IOException ignore) {}
        }

        zipInputStream = new ByteArrayInputStream(bytesOutput.toByteArray());
    } catch (IOException e) {
        e.printStackTrace();
        throw new PersistenceException("Persistence Service could not received input stream to persist for " + uniqueId);
    }

    // ...

在必要的情况下，可以将ByteArrayOutputStream/ByteArrayInputStream替换为File#createTempFile()创建的临时文件上的FileOuputStream/FileInputStream，尤其是在那些流中可能包含大数据而可能溢出计算机可用内存的情况下同时使用时.

You can if necessary replace the ByteArrayOutputStream/ByteArrayInputStream by a FileOuputStream/FileInputStream on a temporary file as created by File#createTempFile(), especially if those streams can contain large data which might overflow machine's available memory when used concurrently.

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