Android 压缩Post请求数据
Android开发中常会用到Post请求发送数据到服务器，有些情况下Post的数据比较大，比如电子市场获取本地应用信息，然后将应用包名，版本号发送给服务器，应用一多，xml数据就庞大了，10KB~30KB都有可能。这是压缩Post的数据就很有必要了。
当然，我们用别的消息格式，如protobuf等效率较高的数据格式也能减少发送的数据，但这会增加服务器和客户端开发人员的工作量，还要花些时间去了解这种数据交换格式。废话不多说，看看下面Post消息体的格式（包含了一个文件上传的Post请求）。
-------------------7d4a6d158c9 Content-Disposition: form-data; name="myfile"; filename="test.txt" <this is file content> -------------------7d4a6d158c9 Content-Disposition: form-data; name="text1" foo -------------------7d4a6d158c9 Content-Disposition: form-data; name="text2" <this is gzipped post field> gzipped size:214 original:416 -------------------7d4a6d158c9--
在这个请求体内，name为text2的字段内容采用了gzip压缩，模拟较大的字符串字段。当字符串上10KB压缩量还是挺可观的 ，可减少一倍到四倍的流量。关于怎么构造这个消息体可以参考这里，特别留意这里
Content-Disposition: form-data; name="text2"
的空格，冒号和分号间分别有空格，不然服务器解析会出错，至于为什么？RFC规定就这么地。
下面看看服务器端构造Post消息体（这个是在之前一篇文件上传的文章上增加的功能）
package com.hoot.regx;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class PostData {
private static final String LONG_STRING = "require 'zlib'equire 'stringio'"
+ "File.open('t1.gz', 'w') do |f| gz = Zlib::GzipWriter.new(f)"
+ " gz.write 'part one' gz.closeendFile.open('t2.gz', 'w') do |f|"
+ " gz = Zlib::GzipWriter.new(f) gz.write 'part 2' gz.close"
+ "endcontents1 = File.open('t1.gz', \"rb\") {|io| io.read }"
+ "contents2 = File.open('t2.gz', \"rb\") {|io| io.read }"
+ "c = contents1 + contents2"
+ "gz = Zlib::GzipReader.new(StringIO.new(c))" + "gz.each do | l |"
+ " puts l" + "end";
private static final String CHAR_SET = "UTF-8";
private static final String BOUNDARY = "-----------------7d4a6d158c9";
private static final String TWO_HYPHENS = "--";
private static final String END = "\r\n";
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
PostData pd = new PostData();
pd.uploadFile();
// pd.uploadXML();
}
public void uploadFile() throws IOException {
URL url = new URL("http://localhost:4567/upload");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setRequestMethod("POST");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setRequestProperty("Charset", CHAR_SET);
conn.setRequestProperty("Content-Type", "multipart/form-data;boundary="
+ BOUNDARY);
StringBuffer sb = new StringBuffer();
// 分解符
sb.append(TWO_HYPHENS + BOUNDARY + END);
// 设置与上次文件相关信息
// 上传文件信息和文件的内容间必须有一个空行，否则会把后面的数据当做属性读
sb.append("Content-Disposition: form-data; name=\"myfile\"; filename=\"test.txt\""
+ END + END);
System.out.print(sb.toString());
byte[] data = sb.toString().getBytes();
OutputStream os = conn.getOutputStream();
os.write(data);
// 一下是文件数据
FileInputStream fis = new FileInputStream(new File("test.txt"));
byte[] buf = new byte[1024];
int len = 0;
while ((len = fis.read(buf)) > 0) {
os.write(buf, 0, len);
}
System.out.print("<this is file content>");
/**
* 注意form-data后面的空格 -----------------------------7d33a816d302b6
*
* Content-Disposition: form-data; name="text1"
*
* foo -----------------------------7d33a816d302b6
*/
String split = END + TWO_HYPHENS + BOUNDARY + END
+ "Content-Disposition: form-data; " + "name=\"text1\" " + END
+ END + "foo"/* + END */;
System.out.print(split);
os.write(split.getBytes());
byte[] b = ZipUtil.compress(LONG_STRING.getBytes());
split = END + TWO_HYPHENS + BOUNDARY + END
+ "Content-Disposition: form-data; " + "name=\"text2\" " + END
+ END/* + dataStr + END */;
System.out.print(split);
os.write(split.getBytes());
os.write(b);
os.write(END.getBytes());
System.out
.print("<this is gzipped post field> gzipped size:" + b.length
+ " original:" + LONG_STRING.getBytes().length + END);
String endStr = TWO_HYPHENS + BOUNDARY + TWO_HYPHENS + END;
byte[] end_data = endStr.getBytes();
System.out.print(endStr);
os.write(end_data);
os.flush();
os.close();
fis.close();
InputStream is = conn.getInputStream();
while ((len = is.read(buf)) > 0) {
System.out.write(buf, 0, len);
}
// is.close();
}
}
以下是压缩字符串的工具类
public static byte[] compress(byte[] data) throws IOException {
if (data == null || data.length == 0) {
return data;
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(out);
gzip.write(data);
gzip.close();
return out.toByteArray();
}
服务器端还是sinatra框架，小巧实用。如果你Servlet顺手，那也无所谓，好久没搞Java EE这套了，忘得差不多了
require 'rubygems'
require 'sinatra'
require 'haml'
require 'zlib'
get '/' do
'Hello world'
end
# Handle GET-request (Show the upload form)
get "/upload" do
haml :upload
end
# Handle POST-request (Receive and save the uploaded file)
post "/upload" do
logger.info "#{params}"
unless params[:myfile] &&
(tmpfile = params[:myfile][:tempfile]) &&
(name = params[:myfile][:filename])
@error = "No file selected"
logger.info "params #{@error} file: #{tmpfile} name: #{name} #{params}"
return haml(:error)
end
directory = 'uploads'
path = File.join(directory, name)
logger.info "name:#{params[:text1]}, #{params[:text2]}"
#gz = Zlib::GzipReader.new(params[:text2])
#print gz.read
#gz.close
logger.info inflate(params[:text2])
File.open(path, "wb") do |f|
f.write(tmpfile.read)
end
@msg = "file #{name} was successfully uploaded!"
end
def inflate(string)
gz = Zlib::GzipReader.new(StringIO.new(params[:text2].force_encoding("UTF-8")))
data = gz.read
end
博文源地址在这里，PS：没想到这边阅读量这么高。。。我可怜的VPS上的博客。。。。