java - 用PHP压缩的字符串与用Java压缩的字符串不匹配

Question

压缩php中的单词“ test”返回
使用该行的“ eNorSS0uAQAEXQHB”


  base64_encode（gzcompress（“ test”，9））


我也想要在Android应用中使用相同的方法。所以，我用下面的代码：

try {
byte[] input = "test".getBytes("UTF-8");
byte[] output = new byte[100];
Deflater compresser = new Deflater();
compresser.setInput(input);
compresser.finish();
compresser.deflate(output);
compresser.end();
return Base64.encodeToString(output, Base64.DEFAULT);
} catch (Exception e) {
return e.getMessage();
}

作为输出


  eJzLz0sFAAKRAUMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
      AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA ==




尝试了另一种方法，如下所示：

try {
 ByteArrayOutputStream out = new ByteArrayOutputStream(str.length());
 GZIPOutputStream gzip = new GZIPOutputStream(out);
 gzip.write(str.getBytes());
 gzip.close();

 byte[] compressedBytes = out.toByteArray();
 return Base64.encodeToString(compressedBytes, Base64.DEFAULT); // I would return compressedBytes instead String
 } catch (Exception e) {
     return e.getMessage();
 }

作为输出


  H4sIAAAAAAAAAMvPSwUA8YZsegMAAAA =


应该使用哪种方法从Java中获取相同的压缩文件（与php中一样）=> eNorSS0uAQAEXQHB

Answer 1

您的方法有两个问题。


该代码未使用相同的压缩级别（PHP-> 9，Java-> 6（默认））
压缩数据的长度（由compresser.deflate(output)返回）被忽略


这是一个冗长的工作示例，用于在Java中生成与PHP代码段相同的Base64输出。

import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.Base64;
import java.util.zip.Deflater;

public class CompressDemo {
    public static void main(String[] args) throws Exception {
        byte[] input = "test".getBytes(StandardCharsets.UTF_8);
        byte[] buffer = new byte[100];
        // create a deflater for the compression to best compression level (9)
        Deflater compresser = new Deflater(Deflater.BEST_COMPRESSION);
        compresser.setInput(input);
        compresser.finish();
        // keep the length of the compressed data
        int compressedDataLength = compresser.deflate(buffer);
        compresser.end();
        // create an array only containing the compressed bytes
        byte[] compressed = Arrays.copyOfRange(buffer, 0, compressedDataLength);
        System.out.println(new String(Base64.getEncoder().encode(compressed)));
    }
}

编辑一个示例，其中缓冲区很小，可以一次存储整个压缩数据。

public static void main(String[] args) throws Exception {
    ByteArrayOutputStream resultBuffer = new ByteArrayOutputStream();
    byte[] input = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".getBytes(StandardCharsets.UTF_8);
    // a buffer to small to hold the compressed data
    byte[] buffer = new byte[10];
    Deflater compresser = new Deflater(Deflater.BEST_COMPRESSION);
    compresser.setInput(input);
    compresser.finish();
    do {
        // compress the input data and fill the buffer
        int compressedDataLength = compresser.deflate(buffer);
        System.out.println("compressedDataLength = " + compressedDataLength);
        // append the compressed data to the result buffer
        resultBuffer.write(buffer, 0, compressedDataLength);
        // continue until all input data were processed
    } while(!compresser.finished());
    compresser.end();
    byte[] compressed = resultBuffer.toByteArray();
    System.out.println(new String(Base64.getEncoder().encode(compressed)));
}

输出

compressedDataLength = 10
compressedDataLength = 10
compressedDataLength = 10
compressedDataLength = 4
eNpzdHJ2cXVz9/D08vbx9fMPCAwKDgkNC4+IjAIAZKYH4A==