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。