android与服务端通讯时使用到的GZIP压缩及解压

为了减小android项目与服务端进行通讯时的数据流量，我们可以使用GZIP对服务端传输的数据进行压缩，在android客户端解压。或在客户端压缩，在服务端解压。代码如下：

android客户端的GZIP操作类：

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import org.kobjects.base64.Base64;

/**
* @author Jinqi 2014/1/27
* GZIP压缩和解压缩的操作类
*
*/
public class GzipHelper {
/** GZIP压缩
* @param str 要压缩的字符串
* @return GZIP压缩后的字符串
* @throws IOException
*/
public static String compress(String str) throws IOException {

byte[] blockcopy = ByteBuffer
.allocate(4)
.order(java.nio.ByteOrder.LITTLE_ENDIAN)
.putInt(str.length())
.array();
ByteArrayOutputStream os = new ByteArrayOutputStream(str.length());
GZIPOutputStream gos = new GZIPOutputStream(os);
gos.write(str.getBytes());
gos.close();
os.close();
byte[] compressed = new byte[4 + os.toByteArray().length];
System.arraycopy(blockcopy, 0, compressed, 0, 4);
System.arraycopy(os.toByteArray(), 0, compressed, 4,
os.toByteArray().length);
return Base64.encode(compressed);

}

/** GZIP解压缩
* @param zipText GZIP压缩过的字符串
* @return 解压后的字符串
* @throws IOException
*/
public static String decompress(String zipText) throws IOException {
byte[] compressed = Base64.decode(zipText);
if (compressed.length > 4)
{
GZIPInputStream gzipInputStream = new GZIPInputStream(
new ByteArrayInputStream(compressed, 4,
compressed.length - 4));

ByteArrayOutputStream baos = new ByteArrayOutputStream();
for (int value = 0; value != -1;) {
value = gzipInputStream.read();
if (value != -1) {
baos.write(value);
}
}
gzipInputStream.close();
baos.close();
String sReturn = new String(baos.toByteArray(), "UTF-8");
return sReturn;
}
else
{
return "";
}
}
}

.net服务端的GZIP操作类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Text;
using System.IO;
using System.IO.Compression;

namespace MobileServ
{
public class ZipHelper
{
public static string compress(string text)
{
byte[] buffer = Encoding.UTF8.GetBytes(text);
MemoryStream ms = new MemoryStream();
using (GZipStream zip = new GZipStream(ms, CompressionMode.Compress, true))
{
zip.Write(buffer, 0, buffer.Length);
}

ms.Position = 0;
MemoryStream outStream = new MemoryStream();

byte[] compressed = new byte[ms.Length];
ms.Read(compressed, 0, compressed.Length);

byte[] gzBuffer = new byte[compressed.Length + 4];
System.Buffer.BlockCopy(compressed, 0, gzBuffer, 4, compressed.Length);
System.Buffer.BlockCopy(BitConverter.GetBytes(buffer.Length), 0, gzBuffer, 0, 4);
return Convert.ToBase64String(gzBuffer);
}

public static string decompress(string compressedText)
{
byte[] gzBuffer = Convert.FromBase64String(compressedText);
using (MemoryStream ms = new MemoryStream())
{
int msgLength = BitConverter.ToInt32(gzBuffer, 0);
ms.Write(gzBuffer, 4, gzBuffer.Length - 4);

byte[] buffer = new byte[msgLength];

ms.Position = 0;
using (GZipStream zip = new GZipStream(ms, CompressionMode.Decompress))
{
zip.Read(buffer, 0, buffer.Length);
}

return Encoding.UTF8.GetString(buffer);
}
}
}
}

通过GIZP压缩及解压，可以将传输的数据压缩1/4左右，效果非常明显。