20

我正在尝试编写一个可以压缩数据的类。以下代码失败（没有抛出异常，但目标 .gz 文件为空。）
此外：我不想像所有示例中那样直接生成 .gz 文件。我只想获取压缩数据，以便在将数据写入文件之前对其进行加密。

如果我直接写入文件一切正常：

import java.io.*;
import java.util.zip.*;
import java.nio.charset.*;

public class Zipper
{
  public static void main(String[] args)
  {    
    byte[] dataToCompress = "This is the test data."
      .getBytes(StandardCharsets.ISO_8859_1);

    GZIPOutputStream zipStream = null;
    FileOutputStream fileStream = null;
    try
    {
      fileStream = new FileOutputStream("C:/Users/UserName/Desktop/zip_file.gz");
      zipStream = new GZIPOutputStream(fileStream);
      zipStream.write(dataToCompress);

      fileStream.write(compressedData);
    }
    catch(Exception e)
    {
      e.printStackTrace();
    }
    finally
    {
      try{ zipStream.close(); }
        catch(Exception e){ }
      try{ fileStream.close(); }
        catch(Exception e){ }
    }
  }
}

但是，如果我想将它“绕过”到字节数组流，它不会产生单个字节 -compressedData总是空的。

import java.io.*;
import java.util.zip.*;
import java.nio.charset.*;

public class Zipper
{
  public static void main(String[] args)
  {    
    byte[] dataToCompress = "This is the test data."
      .getBytes(StandardCharsets.ISO_8859_1);
    byte[] compressedData = null;

    GZIPOutputStream zipStream = null;
    ByteArrayOutputStream byteStream = null;
    FileOutputStream fileStream = null;
    try
    {
      byteStream = new ByteArrayOutputStream(dataToCompress.length);
      zipStream = new GZIPOutputStream(byteStream);
      zipStream.write(dataToCompress);

      compressedData = byteStream.toByteArray();

      fileStream = new FileOutputStream("C:/Users/UserName/Desktop/zip_file.gz");
      fileStream.write(compressedData);
    }
    catch(Exception e)
    {
      e.printStackTrace();
    }
    finally
    {
      try{ zipStream.close(); }
        catch(Exception e){ }
      try{ byteStream.close(); }
        catch(Exception e){ }
      try{ fileStream.close(); }
        catch(Exception e){ }
    }
  }
}
4

7 回答 7

37

问题是您没有关闭GZIPOutputStream. 在您关闭它之前，输出将是不完整的。

您只需要在读取字节数组之前关闭它。您需要重新排序finally块以实现此目的。

import java.io.*;
import java.util.zip.*;
import java.nio.charset.*;

public class Zipper
{
  public static void main(String[] args)
  {    
    byte[] dataToCompress = "This is the test data."
      .getBytes(StandardCharsets.ISO_8859_1);

    try
    {
      ByteArrayOutputStream byteStream =
        new ByteArrayOutputStream(dataToCompress.length);
      try
      {
        GZIPOutputStream zipStream =
          new GZIPOutputStream(byteStream);
        try
        {
          zipStream.write(dataToCompress);
        }
        finally
        {
          zipStream.close();
        }
      }
      finally
      {
        byteStream.close();
      }

      byte[] compressedData = byteStream.toByteArray();

      FileOutputStream fileStream =
        new FileOutputStream("C:/Users/UserName/Desktop/zip_file.gz");
      try
      {
        fileStream.write(compressedData);
      }
      finally
      {
        try{ fileStream.close(); }
          catch(Exception e){ /* We should probably delete the file now? */ }
      }
    }
    catch(Exception e)
    {
      e.printStackTrace();
    }
  }
}

我不建议将流变量初始化为null，因为这意味着您的finally块也可以抛出NullPointerException.

另请注意，您可以声明mainthrow IOException（然后您不需要最外面的try语句。）

吞下 .gz 中的异常没有什么意义zipStream.close();，因为如果它抛出异常，您将没有有效的 .gz 文件（因此您不应该继续编写它。）

此外，我不会吞下异常，byteStream.close();但出于不同的原因——它们永远不应该被抛出（即你的 JRE 中有一个错误，你想知道这一点。）

于 2013-02-09T00:45:52.473 回答
26

我改进了 JITHINRAJ 的代码 - 使用了 try-with-resources：

private static byte[] gzipCompress(byte[] uncompressedData) {
        byte[] result = new byte[]{};
        try (ByteArrayOutputStream bos = new ByteArrayOutputStream(uncompressedData.length);
             GZIPOutputStream gzipOS = new GZIPOutputStream(bos)) {
            gzipOS.write(uncompressedData);
            // You need to close it before using bos
            gzipOS.close();
            result = bos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

private static byte[] gzipUncompress(byte[] compressedData) {
        byte[] result = new byte[]{};
        try (ByteArrayInputStream bis = new ByteArrayInputStream(compressedData);
             ByteArrayOutputStream bos = new ByteArrayOutputStream();
             GZIPInputStream gzipIS = new GZIPInputStream(bis)) {
            byte[] buffer = new byte[1024];
            int len;
            while ((len = gzipIS.read(buffer)) != -1) {
                bos.write(buffer, 0, len);
            }
            result = bos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }
于 2017-07-05T09:29:06.007 回答
6

如果您仍在寻找答案，您可以使用以下代码使用 deflater 获取压缩的 byte[] 并使用 inflater 对其进行解压缩。

public static void main(String[] args) {
        //Some string for testing
        String sr = new String("fsdfesfsfdddddddsfdsfssdfdsfdsfdsfdsfdsdfggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggghghghghggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggfsdfesfsfdddddddsfdsfssdfdsfdsfdsfdsfdsdfggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggghghghghggggggggggggggggggggggggggggggggggggggggg");
        byte[] data = sr.getBytes();
        System.out.println("src size "+data.length);
        try {
            compress(data);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public static byte[] compress(byte[] data) throws IOException { 
        Deflater deflater = new Deflater(); 
        deflater.setInput(data); 
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);  

        deflater.finish(); 
        byte[] buffer = new byte[1024];  
        while (!deflater.finished()) { 
        int count = deflater.deflate(buffer);  
        outputStream.write(buffer, 0, count);  
        } 
        outputStream.close(); 
        byte[] output = outputStream.toByteArray(); 

        System.out.println("Original: " + data.length  ); 
        System.out.println("Compressed: " + output.length ); 
        return output; 
        }
于 2014-10-14T10:10:25.287 回答
2

压缩

private static byte[] compress(byte[] uncompressedData) {
        ByteArrayOutputStream bos = null;
        GZIPOutputStream gzipOS = null;
        try {
            bos = new ByteArrayOutputStream(uncompressedData.length);
            gzipOS = new GZIPOutputStream(bos);
            gzipOS.write(uncompressedData);
            gzipOS.close();
            return bos.toByteArray();

        } catch (IOException e) {
            e.printStackTrace();
        }
        finally {
            try {
                assert gzipOS != null;
                gzipOS.close();
                bos.close();
            }
            catch (Exception ignored) {
            }
        }
        return new byte[]{};
    }

解压缩

private byte[] uncompress(byte[] compressedData) {
        ByteArrayInputStream bis = null;
        ByteArrayOutputStream bos = null;
        GZIPInputStream gzipIS = null;

        try {
            bis = new ByteArrayInputStream(compressedData);
            bos = new ByteArrayOutputStream();
            gzipIS = new GZIPInputStream(bis);

            byte[] buffer = new byte[1024];
            int len;
            while((len = gzipIS.read(buffer)) != -1){
                bos.write(buffer, 0, len);
            }
            return bos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        finally {
            try {
                assert gzipIS != null;
                gzipIS.close();
                bos.close();
                bis.close();
            }
            catch (Exception e) {
                e.printStackTrace();
            }
        }
        return new byte[]{};
    }
于 2017-06-23T11:17:29.557 回答
1

您可以使用以下功能，它已经过测试并且工作正常。

通常，您的代码存在忽略异常的严重问题！返回null或根本不打印catch块中的任何内容将使调试变得非常困难

如果您想进一步处理它（例如加密），您不必将 zip 输出写入文件，您可以轻松修改代码以将输出写入内存流

public static String zip(File inFile, File zipFile) throws IOException {        
    FileInputStream fis = new FileInputStream(inFile);
    FileOutputStream fos = new FileOutputStream(zipFile);
    ZipOutputStream zout = new ZipOutputStream(fos);

    try {
        zout.putNextEntry(new ZipEntry(inFile.getName()));
        byte[] buffer = new byte[BUFFER_SIZE];
        int len;
        while ((len = fis.read(buffer)) > 0) {
            zout.write(buffer, 0, len);
        }
        zout.closeEntry();
    } catch (Exception ex) {
        ex.printStackTrace();
        return null;
    } finally {
        try{zout.close();}catch(Exception ex){ex.printStackTrace();}
        try{fis.close();}catch(Exception ex){ex.printStackTrace();}         
    }
    return zipFile.getAbsolutePath();
}
于 2013-02-08T17:49:11.060 回答
0

试试这个代码..

try {
    String inputFileName = "test.txt";  //may use your file_Path
    String zipFileName = "compressed.zip";

    //Create input and output streams
    FileInputStream inStream = new FileInputStream(inputFileName);
    ZipOutputStream outStream = new ZipOutputStream(new FileOutputStream(zipFileName));

    // Add a zip entry to the output stream
    outStream.putNextEntry(new ZipEntry(inputFileName));

    byte[] buffer = new byte[1024];
    int bytesRead;

    //Each chunk of data read from the input stream
    //is written to the output stream
    while ((bytesRead = inStream.read(buffer)) > 0) {
        outStream.write(buffer, 0, bytesRead);
    }

    //Close zip entry and file streams
    outStream.closeEntry();

    outStream.close();
    inStream.close();

} catch (IOException ex) {
    ex.printStackTrace();
}

也可能对这个有帮助..

于 2013-02-08T17:28:18.213 回答
0

大多数示例都有错误的异常处理。

public static byte[] gzipBytes(byte[] payload) {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    try (GZIPOutputStream gzip = new GZIPOutputStream(baos)) {
        gzip.write(payload);
    } catch (IOException e) {
        throw new UncheckedIOException(e);
    }
    // note: toByteArray should be called after try-with-resources, not inside
    return baos.toByteArray();
}

public static byte[] gunzipBytes(byte[] gzPayload) {
    ByteArrayInputStream bais = new ByteArrayInputStream(gzPayload);
    try (GZIPInputStream gzip = new GZIPInputStream(bais)) {
        // java 9+ required for this method
        return gzip.readAllBytes();
    } catch (IOException e) {
        throw new UncheckedIOException("Error while unpacking gzip content", e);
    }
}
于 2022-02-26T15:48:58.340 回答