Java中使用Deflate和Inflate类的Zlib压缩
我想尝试使用java.util.zip中的Deflate和Inflate类进行zlib压缩 我可以使用Deflate压缩代码,但是在解压缩时,我遇到了这个错误-Java中使用Deflate和Inflate类的Zlib压缩,java,compression,zlib,deflate,inflate,Java,Compression,Zlib,Deflate,Inflate,我想尝试使用java.util.zip中的Deflate和Inflate类进行zlib压缩 我可以使用Deflate压缩代码,但是在解压缩时,我遇到了这个错误- Exception in thread "main" java.util.zip.DataFormatException: unknown compression method at java.util.zip.Inflater.inflateBytes(Native Method) at java.util.zip.I
Exception in thread "main" java.util.zip.DataFormatException: unknown compression method
at java.util.zip.Inflater.inflateBytes(Native Method)
at java.util.zip.Inflater.inflate(Inflater.java:238)
at java.util.zip.Inflater.inflate(Inflater.java:256)
at zlibCompression.main(zlibCompression.java:53)
这是到目前为止我的代码-
import java.util.zip.*;
import java.io.*;
public class zlibCompression {
/**
* @param args
*/
public static void main(String[] args) throws IOException, DataFormatException {
// TODO Auto-generated method stub
String fname = "book1";
FileReader infile = new FileReader(fname);
BufferedReader in = new BufferedReader(infile);
FileOutputStream out = new FileOutputStream("book1out.dfl");
//BufferedInputStream in = new BufferedInputStream(new FileInputStream(filename));
Deflater compress = new Deflater();
Inflater decompress = new Inflater();
String readFile = in.readLine();
byte[] bx = readFile.getBytes();
while(readFile!=null){
byte[] input = readFile.getBytes();
byte[] compressedData = new byte[1024];
compress.setInput(input);
compress.finish();
int compressLength = compress.deflate(compressedData, 0, compressedData.length);
//System.out.println(compressedData);
out.write(compressedData, 0, compressLength);
readFile = in.readLine();
}
File abc = new File("book1out.dfl");
InputStream is = new FileInputStream("book1out.dfl");
InflaterInputStream infl = new InflaterInputStream(new FileInputStream("book1out.dfl"), new Inflater());
FileOutputStream outFile = new FileOutputStream("decompressed.txt");
byte[] b = new byte[1024];
while(true){
int a = infl.read(b,0,1024);
if(a==0)
break;
decompress.setInput(b);
byte[] fresult = new byte[1024];
//decompress.in
int resLength = decompress.inflate(fresult);
//outFile.write(b,0,1);
//String outt = new String(fresult, 0, resLength);
//System.out.println(outt);
}
System.out.println("complete");
}
}
你想在这里干什么?您使用一个充气器输入流来解压缩您的数据,然后尝试再次将此解压缩数据传递给充气器?使用其中一个,但不能同时使用两个 这就是导致您出现异常的原因 除此之外,还有一些小错误,如bestsss提到的:
- 在循环中完成压缩-完成后,无法添加更多数据
- 您不会检查放气过程产生的输出量。如果您有长行,则可能超过1024字节
- 您设置了充气机的输入,但也没有设置长度
a
- 写入后(以及从同一文件读取前)不会关闭FileOutputStream
- 您可以使用
读取一行文本,但不需要再次添加换行符,这意味着解压文件中不会出现任何换行符readLine()
- 您无需将字节转换为字符串,然后再转换为字节
- 您创建了以后不使用的变量
那是家庭作业吗?一个错误是调用finish太早,另一个错误是使用setInput w/o length,还有一个错误是没有检查deflate进程返回的数据是否超过1024。您确定这是针对zlib的吗。我试图解压缩zlib文件,但得到了一个
未知的压缩方法
错误。如果我看一下,我会看到充气机
提到zlib,但您使用的充气机输入流
提到了放气压缩方法。这是文件:InflaterInputStream使用一个新充气器()
(如果使用不带充气器参数的构造函数)。这个构造函数使用nowrap=false
,这意味着zlib压缩。(我没有检查你的文件。)扫描仪的目标是什么?刚刚获取流的第一行?@Paŭlo Ebermann:这是一个一次性读取整个流的技巧。为什么缓冲(输入输出)putStream
不存在?Stephan:没有特别的原因,代码工作正常。也许更大的文件包含缓冲版本会更快
import java.util.zip.*;
import java.io.*;
/**
* Example program to demonstrate how to use zlib compression with
* Java.
* Inspired by http://stackoverflow.com/q/6173920/600500.
*/
public class ZlibCompression {
/**
* Compresses a file with zlib compression.
*/
public static void compressFile(File raw, File compressed)
throws IOException
{
InputStream in = new FileInputStream(raw);
OutputStream out =
new DeflaterOutputStream(new FileOutputStream(compressed));
shovelInToOut(in, out);
in.close();
out.close();
}
/**
* Decompresses a zlib compressed file.
*/
public static void decompressFile(File compressed, File raw)
throws IOException
{
InputStream in =
new InflaterInputStream(new FileInputStream(compressed));
OutputStream out = new FileOutputStream(raw);
shovelInToOut(in, out);
in.close();
out.close();
}
/**
* Shovels all data from an input stream to an output stream.
*/
private static void shovelInToOut(InputStream in, OutputStream out)
throws IOException
{
byte[] buffer = new byte[1000];
int len;
while((len = in.read(buffer)) > 0) {
out.write(buffer, 0, len);
}
}
/**
* Main method to test it all.
*/
public static void main(String[] args) throws IOException, DataFormatException {
File compressed = new File("book1out.dfl");
compressFile(new File("book1"), compressed);
decompressFile(compressed, new File("decompressed.txt"));
}
}
import java.util.Scanner;
import java.util.zip.*;
import java.io.*;
public class ZLibCompression
{
public static void compress(File raw, File compressed) throws IOException
{
try (InputStream inputStream = new FileInputStream(raw);
OutputStream outputStream = new DeflaterOutputStream(new FileOutputStream(compressed)))
{
copy(inputStream, outputStream);
}
}
public static void decompress(File compressed, File raw)
throws IOException
{
try (InputStream inputStream = new InflaterInputStream(new FileInputStream(compressed));
OutputStream outputStream = new FileOutputStream(raw))
{
copy(inputStream, outputStream);
}
}
public static String decompress(File compressed) throws IOException
{
try (InputStream inputStream = new InflaterInputStream(new FileInputStream(compressed)))
{
return toString(inputStream);
}
}
private static String toString(InputStream inputStream)
{
try (Scanner scanner = new Scanner(inputStream).useDelimiter("\\A"))
{
return scanner.hasNext() ? scanner.next() : "";
}
}
private static void copy(InputStream inputStream, OutputStream outputStream)
throws IOException
{
byte[] buffer = new byte[1000];
int length;
while ((length = inputStream.read(buffer)) > 0)
{
outputStream.write(buffer, 0, length);
}
}
}