47

我正在使用以下代码压缩和解压缩字符串数据，但我面临的问题是，它很容易被压缩而没有错误，但解压缩方法会引发以下错误。

线程“主”java.io.IOException 中的异常：不是 GZIP 格式

public static void main(String[] args) throws Exception {
        String string = "I am what I am hhhhhhhhhhhhhhhhhhhhhhhhhhhhh"
                + "bjggujhhhhhhhhh"
                + "rggggggggggggggggggggggggg"
                + "esfffffffffffffffffffffffffffffff"
                + "esffffffffffffffffffffffffffffffff"
                + "esfekfgy enter code here`etd`enter code here wdd"
                + "heljwidgutwdbwdq8d"
                + "skdfgysrdsdnjsvfyekbdsgcu"
                +"jbujsbjvugsduddbdj";

       System.out.println("after compress:");
        String compressed = compress(string);
        System.out.println(compressed);
        System.out.println("after decompress:");
        String decomp = decompress(compressed);
        System.out.println(decomp);
    }


     public static String compress(String str) throws Exception {
        if (str == null || str.length() == 0) {
            return str;
        }
        System.out.println("String length : " + str.length());
        ByteArrayOutputStream obj=new ByteArrayOutputStream();
        GZIPOutputStream gzip = new GZIPOutputStream(obj);
        gzip.write(str.getBytes("UTF-8"));
        gzip.close();
        String outStr = obj.toString("UTF-8");
        System.out.println("Output String length : " + outStr.length());
        return outStr;
     }

      public static String decompress(String str) throws Exception {
        if (str == null || str.length() == 0) {
            return str;
        }
        System.out.println("Input String length : " + str.length());
        GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(str.getBytes("UTF-8")));
        BufferedReader bf = new BufferedReader(new InputStreamReader(gis, "UTF-8"));
        String outStr = "";
        String line;
        while ((line=bf.readLine())!=null) {
          outStr += line;
        }
        System.out.println("Output String lenght : " + outStr.length());
        return outStr;
     }

还是不知道怎么解决这个问题！！！

4

7 回答 7

45

这是因为

String outStr = obj.toString("UTF-8");

发送byte[]你可以从你那里得到的ByteArrayOutputStream并在你的中使用它ByteArrayInputStream来构建你的GZIPInputStream. 以下是需要在您的代码中完成的更改。

byte[] compressed = compress(string); //In the main method

public static byte[] compress(String str) throws Exception {
    ...
    ...
    return obj.toByteArray();
}

public static String decompress(byte[] bytes) throws Exception {
    ...
    GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(bytes));
    ...
}
于 2013-05-03T04:51:13.473 回答
34

上面的答案解决了我们的问题，但除此之外。如果我们尝试解压缩未压缩的（“非 zip 格式”）字节 []。我们将收到“不是 GZIP 格式”异常消息。

为了解决这个问题，我们可以在我们的类中添加附加代码。

public static boolean isCompressed(final byte[] compressed) {
    return (compressed[0] == (byte) (GZIPInputStream.GZIP_MAGIC)) && (compressed[1] == (byte) (GZIPInputStream.GZIP_MAGIC >> 8));
}

我的完整压缩类与压缩/解压缩看起来像：

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

public class GZIPCompression {
  public static byte[] compress(final String str) throws IOException {
    if ((str == null) || (str.length() == 0)) {
      return null;
    }
    ByteArrayOutputStream obj = new ByteArrayOutputStream();
    GZIPOutputStream gzip = new GZIPOutputStream(obj);
    gzip.write(str.getBytes("UTF-8"));
    gzip.flush();
    gzip.close();
    return obj.toByteArray();
  }

  public static String decompress(final byte[] compressed) throws IOException {
    final StringBuilder outStr = new StringBuilder();
    if ((compressed == null) || (compressed.length == 0)) {
      return "";
    }
    if (isCompressed(compressed)) {
      final GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(compressed));
      final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(gis, "UTF-8"));

      String line;
      while ((line = bufferedReader.readLine()) != null) {
        outStr.append(line);
      }
    } else {
      outStr.append(compressed);
    }
    return outStr.toString();
  }

  public static boolean isCompressed(final byte[] compressed) {
    return (compressed[0] == (byte) (GZIPInputStream.GZIP_MAGIC)) && (compressed[1] == (byte) (GZIPInputStream.GZIP_MAGIC >> 8));
  }
}
于 2015-12-16T06:20:36.917 回答
14

如果您需要通过网络传输压缩内容或将其存储为文本，则必须使用 Base64 编码器（例如 apache commons codec Base64）将字节数组转换为 Base64 字符串，并将字符串解码回字节数组远程客户端。在使用 Zip Stream 和 Base64 编码器压缩大字符串数据中找到了一个示例！

于 2013-11-13T02:55:00.440 回答
9

另一个正确压缩和解压的例子：

@Slf4j
public class GZIPCompression {
    public static byte[] compress(final String stringToCompress) {
        if (isNull(stringToCompress) || stringToCompress.length() == 0) {
            return null;
        }

        try (final ByteArrayOutputStream baos = new ByteArrayOutputStream();
            final GZIPOutputStream gzipOutput = new GZIPOutputStream(baos)) {
            gzipOutput.write(stringToCompress.getBytes(UTF_8));
            gzipOutput.finish();
            return baos.toByteArray();
        } catch (IOException e) {
            throw new UncheckedIOException("Error while compression!", e);
        }
    }

    public static String decompress(final byte[] compressed) {
        if (isNull(compressed) || compressed.length == 0) {
            return null;
        }

        try (final GZIPInputStream gzipInput = new GZIPInputStream(new ByteArrayInputStream(compressed));
             final StringWriter stringWriter = new StringWriter()) {
            IOUtils.copy(gzipInput, stringWriter, UTF_8);
            return stringWriter.toString();
        } catch (IOException e) {
            throw new UncheckedIOException("Error while decompression!", e);
        }
    }
}
于 2017-10-11T12:39:08.293 回答
7

问题是这一行：

    String outStr = obj.toString("UTF-8");

字节数组obj包含任意二进制数据。您不能像 UTF-8 一样“解码”任意二进制数据。如果你尝试，你会得到一个不能被“编码”回字节的字符串。或者至少，您获得的字节将与您开始时的不同......在某种程度上它们不再是有效的 GZIP 流。

解决方法是按原样存储或传输字节数组的内容。不要尝试将其转换为字符串。它是二进制数据，而不是文本。

于 2013-05-03T04:48:26.840 回答
4

客户端发送一些需要压缩的消息，服务器（kafka）解压字符串消息

以下是我的示例：

压缩：

   public static String compress(String str, String inEncoding) {
        if (str == null || str.length() == 0) {
            return str;
        }
        try {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            GZIPOutputStream gzip = new GZIPOutputStream(out);
            gzip.write(str.getBytes(inEncoding));
            gzip.close();
            return URLEncoder.encode(out.toString("ISO-8859-1"), "UTF-8");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

解压：

    public static String decompress(String str, String outEncoding) {
        if (str == null || str.length() == 0) {
            return str;
        }

        try {
            String decode = URLDecoder.decode(str, "UTF-8");

            ByteArrayOutputStream out = new ByteArrayOutputStream();
            ByteArrayInputStream in = new ByteArrayInputStream(decode.getBytes("ISO-8859-1"));
            GZIPInputStream gunzip = new GZIPInputStream(in);
            byte[] buffer = new byte[256];
            int n;
            while ((n = gunzip.read(buffer)) >= 0) {
                out.write(buffer, 0, n);
            }
            return out.toString(outEncoding);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
于 2019-07-19T06:54:08.133 回答
1

您不能将二进制数据转换为字符串。作为一种解决方案，您可以对二进制数据进行编码，然后转换为字符串。例如，看看这个How do you convert binary data to Strings and back in Java?

于 2017-09-06T18:50:23.250 回答