轉自http://snowolf.iteye.com/blog/465433
壓縮代碼如下
/**
* 2009-9-9
*/
package org.zlex.commons.io;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
/**
* ZLib壓縮工具
*
* @author <a href="mailto:[email protected]">樑棟</a>
* @version 1.0
* @since 1.0
*/
public abstract class ZLibUtils {
/**
* 壓縮
*
* @param data
* 待壓縮數據
* @return byte[] 壓縮後的數據
*/
public static byte[] compress(byte[] data) {
byte[] output = new byte[0];
Deflater compresser = new Deflater();
compresser.reset();
compresser.setInput(data);
compresser.finish();
ByteArrayOutputStream bos = new ByteArrayOutputStream(data.length);
try {
byte[] buf = new byte[1024];
while (!compresser.finished()) {
int i = compresser.deflate(buf);
bos.write(buf, 0, i);
}
output = bos.toByteArray();
} catch (Exception e) {
output = data;
e.printStackTrace();
} finally {
try {
bos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
compresser.end();
return output;
}
/**
* 壓縮
*
* @param data
* 待壓縮數據
*
* @param os
* 輸出流
*/
public static void compress(byte[] data, OutputStream os) {
DeflaterOutputStream dos = new DeflaterOutputStream(os);
try {
dos.write(data, 0, data.length);
dos.finish();
dos.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 解壓縮
*
* @param data
* 待壓縮的數據
* @return byte[] 解壓縮後的數據
*/
public static byte[] decompress(byte[] data) {
byte[] output = new byte[0];
Inflater decompresser = new Inflater();
decompresser.reset();
decompresser.setInput(data);
ByteArrayOutputStream o = new ByteArrayOutputStream(data.length);
try {
byte[] buf = new byte[1024];
while (!decompresser.finished()) {
int i = decompresser.inflate(buf);
o.write(buf, 0, i);
}
output = o.toByteArray();
} catch (Exception e) {
output = data;
e.printStackTrace();
} finally {
try {
o.close();
} catch (IOException e) {
e.printStackTrace();
}
}
decompresser.end();
return output;
}
/**
* 解壓縮
*
* @param is
* 輸入流
* @return byte[] 解壓縮後的數據
*/
public static byte[] decompress(InputStream is) {
InflaterInputStream iis = new InflaterInputStream(is);
ByteArrayOutputStream o = new ByteArrayOutputStream(1024);
try {
int i = 1024;
byte[] buf = new byte[i];
while ((i = iis.read(buf, 0, i)) > 0) {
o.write(buf, 0, i);
}
} catch (IOException e) {
e.printStackTrace();
}
return o.toByteArray();
}
}
測試用例代碼如下： /** * 2009-9-9 */ package org.zlex.commons.io; import static org.junit.Assert.*; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import org.junit.Test; /** * ZLib壓縮測試用例 * * @author <a href="mailto:[email protected]">樑棟</a> * @version 1.0 * @since 1.0 */ public class ZLibUtilsTest { @Test public final void testBytes() { System.err.println("字節壓縮／解壓縮測試"); String inputStr = "[email protected];[email protected];[email protected]"; System.err.println("輸入字符串:\t" + inputStr); byte[] input = inputStr.getBytes(); System.err.println("輸入字節長度:\t" + input.length); byte[] data = ZLibUtils.compress(input); System.err.println("壓縮後字節長度:\t" + data.length); byte[] output = ZLibUtils.decompress(data); System.err.println("解壓縮後字節長度:\t" + output.length); String outputStr = new String(output); System.err.println("輸出字符串:\t" + outputStr); assertEquals(inputStr, outputStr); } @Test public final void testFile() { String filename = "zlib"; File file = new File(filename); System.err.println("文件壓縮／解壓縮測試"); String inputStr = "[email protected];[email protected];[email protected]"; System.err.println("輸入字符串:\t" + inputStr); byte[] input = inputStr.getBytes(); System.err.println("輸入字節長度:\t" + input.length); try { FileOutputStream fos = new FileOutputStream(file); ZLibUtils.compress(input, fos); fos.close(); System.err.println("壓縮後字節長度:\t" + file.length()); } catch (Exception e) { fail(e.getMessage()); } byte[] output = null; try { FileInputStream fis = new FileInputStream(file); output = ZLibUtils.decompress(fis); fis.close(); } catch (Exception e) { fail(e.getMessage()); } System.err.println("解壓縮後字節長度:\t" + output.length); String outputStr = new String(output); System.err.println("輸出字符串:\t" + outputStr); assertEquals(inputStr, outputStr); } } 輸入結果 字節壓縮／解壓縮測試 輸入字符串: [email protected];[email protected];[email protected] 輸入字節長度: 59 壓縮後字節長度: 39 解壓縮後字節長度: 59 輸出字符串: [email protected];[email protected];[email protected] 文件壓縮／解壓縮測試 輸入字符串: [email protected];[email protected];[email protected] 輸入字節長度: 59 壓縮後字節長度: 39 解壓縮後字節長度: 59 輸出字符串: [email protected];[email protected];[email protected] 應該怎麼計算呢？原數據長度59字節，壓縮後39字節，大約是33％的壓縮率！ ZLib壓縮對大字節數據壓縮，才能反映出壓縮效果。 先佔個位兒，回頭細緻整理！