发表更新java7 分钟读完 (大约1081个字)

java 压缩

GZIP

  • https://nowjava.com/book/java-example/11374
  • Java GZIP Example – Compress and Decompress File
  • java GZIP压缩与解压缩
  • https://blog.csdn.net/wenqisun/article/details/51121460
  • string
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    public static byte[] compress(String str, String encoding) {
            if (str == null || str.length() == 0) {
                return null;
            }
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            GZIPOutputStream gzip;
            try {
                gzip = new GZIPOutputStream(out);
                gzip.write(str.getBytes(encoding));
                gzip.close();
            } catch ( Exception e) {
                e.printStackTrace();
            }
            return out.toByteArray();
        }
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    public static byte[] uncompress(byte[] bytes) {
            if (bytes == null || bytes.length == 0) {
                return null;
            }
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            ByteArrayInputStream in = new ByteArrayInputStream(bytes);
            try {
                GZIPInputStream ungzip = new GZIPInputStream(in);
                byte[] buffer = new byte[256];
                int n;
                while ((n = ungzip.read(buffer)) >= 0) {
                    out.write(buffer, 0, n);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            return out.toByteArray();
        }
  • file
  • compress-a-file-in-gzip-format-in-java/
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    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.util.zip.GZIPOutputStream;
     
    public class CompressFileGzip {
     
        public static void main(String[] args) {
     
             
            String source_filepath = "C:\\Users\\nikos7\\Desktop\\files\\test.txt";
            String destinaton_zip_filepath = "C:\\Users\\nikos7\\Desktop\\files\\test.gzip";
     
            CompressFileGzip gZipFile = new CompressFileGzip();
            gZipFile.gzipFile(source_filepath, destinaton_zip_filepath);
        }
     
        public void gzipFile(String source_filepath, String destinaton_zip_filepath) {
     
            byte[] buffer = new byte[1024];
     
            try {
                 
                FileOutputStream fileOutputStream =new FileOutputStream(destinaton_zip_filepath);
     
                GZIPOutputStream gzipOuputStream = new GZIPOutputStream(fileOutputStream);
     
                FileInputStream fileInput = new FileInputStream(source_filepath);
     
                int bytes_read;
                 
                while ((bytes_read = fileInput.read(buffer)) > 0) {
                    gzipOuputStream.write(buffer, 0, bytes_read);
                }
     
                fileInput.close();
     
                gzipOuputStream.finish();
                gzipOuputStream.close();
     
                System.out.println("The file was compressed successfully!");
     
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
     
    }
  • compressing-decompressing-files-using-gzip-format-java/
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    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.util.zip.GZIPInputStream;
      
    class GeeksForGeeks
    {
        static final String INPUT_FILE 
                = "/home/saket/Desktop/GeeksforGeeks/compress.gz";
        static final String OUTPUT_FILE 
                = "/home/saket/Desktop//GeeksforGeeks/decompress.java";
          
        static void decompress()
        {
            byte[] buffer = new byte[1024];
            try
            {
                GZIPInputStream is = 
                        new GZIPInputStream(new FileInputStream(INPUT_FILE));
                          
                FileOutputStream out =
                        new FileOutputStream(OUTPUT_FILE);
                  
                int totalSize;
                while((totalSize = is.read(buffer)) > 0 )
                {
                    out.write(buffer, 0, totalSize);
                }
                  
                out.close();
                is.close();
                  
                System.out.println("File Successfully decompressed");
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
              
        }
          
        public static void main (String[] args)
        {
            decompress();
              
        }
    }

    Deflater / Inflater

  • https://cloud.tencent.com/developer/article/1673594
  • https://www.cnblogs.com/zohnn/p/12899931.html
  • JDK 之 Deflater 压缩与 Inflater 解压
  • 关于Inflater和Deflater的简单用法
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    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.util.Random;
    import java.util.zip.DataFormatException;
    import java.util.zip.Deflater;
    import java.util.zip.Inflater;

    public class DeflaterDemo2 {
    	public static void main(String[] args) throws DataFormatException, IOException {
    		StringBuilder builder = new StringBuilder();
    		for (int i = 0; i < 100000; i++) {
    			builder.append("Welcome to TutorialsPoint.com" + (new Random().nextInt() * 26));
    		}
    		String text = builder.toString();
    		byte[] compres = compress(text.getBytes(), true);
    		System.out.println(compres.length + " : " + text.getBytes().length);
    		String res = uncompress(compres, true);
    		System.out.println(res.equals(text));

    		byte[] compres2 = compress(text.getBytes(), false);
    		System.out.println(compres2.length + " : " + text.getBytes().length);
    		String res2 = uncompress(compres2, false);
    		System.out.println(res2.equals(text));
    	}

    	public static String uncompress(byte[] input, boolean nowrap) throws IOException {
    		Inflater inflater = new Inflater(nowrap);
    		inflater.setInput(input);
    		ByteArrayOutputStream baos = new ByteArrayOutputStream(input.length);
    		try {
    			byte[] buff = new byte[1024];
    			while (!inflater.finished()) {
    				int count = inflater.inflate(buff);
    				baos.write(buff, 0, count);
    			}
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			baos.close();
    		}
    		inflater.end();
    		byte[] output = baos.toByteArray();
    		return new String(output);
    	}

    	public static byte[] compress(byte[] data, boolean nowrap) throws IOException {
    		byte[] output;
    		Deflater compress = new Deflater(Deflater.DEFAULT_COMPRESSION, nowrap);

    		compress.reset();
    		compress.setInput(data);
    		compress.finish();
    		ByteArrayOutputStream bos = new ByteArrayOutputStream(data.length);
    		try {
    			byte[] buf = new byte[1024];
    			while (!compress.finished()) {
    				int i = compress.deflate(buf);
    				bos.write(buf, 0, i);
    			}
    			output = bos.toByteArray();
    		} catch (Exception e) {
    			output = data;
    			e.printStackTrace();
    		} finally {
    			bos.close();
    		}
    		compress.end();
    		return output;
    	}

    }

    ZIP

  • Zipping and Unzipping in Java

org.apache.commons.codec.binary.Base64

  • Java字符串的压缩与解压缩的两种方法
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    /**
     * 使用org.apache.commons.codec.binary.Base64压缩字符串
     * @param str 要压缩的字符串
     * @return
     */
    public static String compress(String str) {
      if (str == null || str.length() == 0) {
        return str;
      }//加入Java开发交流君样：756584822一起吹水聊天
      return Base64.encodeBase64String(str.getBytes());
    }
      
    /**
     * 使用org.apache.commons.codec.binary.Base64解压缩
     * @param compressedStr 压缩字符串
     * @return
     */
    public static String uncompress(String compressedStr) {
      if (compressedStr == null) {
        return null;
      }
      return Base64.decodeBase64(compressedStr);
    }
    注意事项

在web项目中，服务器端将加密后的字符串返回给前端，前端再通过ajax请求将加密字符串发送给服务器端处理的时候，在http传输过程中会改变加密字符串的内容，导致服务器解压压缩字符串发生异常：

java.util.zip.ZipException: Not in GZIP format
解决方法：

在字符串压缩之后，将压缩后的字符串BASE64加密，在使用的时候先BASE64解密再解压即可。

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