使用HttpUrlConnection进行post请求上传文件

使用HttpUrlConnection模拟post表单进行文件上传平时很少使用，比较麻烦。

原理是： 分析文件上传的数据格式，然后根据格式构造相应的发送给服务器的字符串。

格式如下：这里的httppost123是我自己构造的字符串，可以是其他任何的字符串

----------httppost123 （\r\n）

Content-Disposition: form-data; name="img"; filename="t.txt" （\r\n）

Content-Type: application/octet-stream （\r\n）

（\r\n）

sdfsdfsdfsdfsdf （\r\n）

----------httppost123 （\r\n）

Content-Disposition: form-data; name="text" （\r\n）

（\r\n）

text tttt （\r\n）

----------httppost123-- （\r\n）

（\r\n）

上面的（\r\n）表示各个数据必须以（\r\n）结尾。

具体Java代码如下：

Java代码


import java.io.ByteArrayOutputStream;

import java.io.DataOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.SocketTimeoutException;

import java.net.URL;

import java.net.URLEncoder;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import javax.imageio.ImageIO;

import javax.imageio.ImageReader;

import javax.imageio.stream.ImageInputStream;

public class HttpPostUtil {

URL url;

HttpURLConnection conn;

String boundary = "--------httppost123";

Map<String, String> textParams = new HashMap<String, String>();

Map<String, File> fileparams = new HashMap<String, File>();

DataOutputStream ds;

public HttpPostUtil(String url) throws Exception {

this.url = new URL(url);

}

//重新设置要请求的服务器地址，即上传文件的地址。

public void setUrl(String url) throws Exception {

this.url = new URL(url);

}

//增加一个普通字符串数据到form表单数据中

public void addTextParameter(String name, String value) {

textParams.put(name, value);

}

//增加一个文件到form表单数据中

public void addFileParameter(String name, File value) {

fileparams.put(name, value);

}

// 清空所有已添加的form表单数据

public void clearAllParameters() {

textParams.clear();

fileparams.clear();

}

// 发送数据到服务器，返回一个字节包含服务器的返回结果的数组

public byte[] send() throws Exception {

initConnection();

try {

conn.connect();

} catch (SocketTimeoutException e) {

// something

throw new RuntimeException();

}

ds = new DataOutputStream(conn.getOutputStream());

writeFileParams();

writeStringParams();

paramsEnd();

InputStream in = conn.getInputStream();

ByteArrayOutputStream out = new ByteArrayOutputStream();

int b;

while ((b = in.read()) != -1) {

out.write(b);

}

conn.disconnect();

return out.toByteArray();

}

//文件上传的connection的一些必须设置

private void initConnection() throws Exception {

conn = (HttpURLConnection) this.url.openConnection();

conn.setDoOutput(true);

conn.setUseCaches(false);

conn.setConnectTimeout(10000); //连接超时为10秒

conn.setRequestMethod("POST");

conn.setRequestProperty("Content-Type",

"multipart/form-data; boundary=" + boundary);

conn.setRequestProperty("connection", "Keep-Alive");

conn.setRequestProperty("Charsert", "UTF-8");

conn.setRequestProperty("Accept-Charset",
"UTF-8");

}

//普通字符串数据

private void writeStringParams() throws Exception {

Set<String> keySet = textParams.keySet();

for (Iterator<String> it = keySet.iterator(); it.hasNext();) {

String name = it.next();

String value = textParams.get(name);

ds.writeBytes("--" + boundary + "\r\n");

ds.writeBytes("Content-Disposition: form-data; name=\"" + name

+ "\"\r\n");

ds.writeBytes("\r\n");

ds.writeBytes(encode(value) + "\r\n");

}

}

//文件数据

private void writeFileParams() throws Exception {

Set<String> keySet = fileparams.keySet();

for (Iterator<String> it = keySet.iterator(); it.hasNext();) {

String name = it.next();

File value = fileparams.get(name);

ds.writeBytes("--" + boundary + "\r\n");

ds.writeBytes("Content-Disposition: form-data; name=\"" + name

+ "\"; filename=\"" + encode(value.getName()) + "\"\r\n");

ds.writeBytes("Content-Type: " + getContentType(value) + "\r\n");

ds.writeBytes("\r\n");

ds.write(getBytes(value));

ds.writeBytes("\r\n");

}

}

//获取文件的上传类型，图片格式为image/png,image/jpg等。非图片为application/octet-stream

private String getContentType(File f) throws Exception {

// return "application/octet-stream"; // 此行不再细分是否为图片，全部作为application/octet-stream 类型

ImageInputStream imagein = ImageIO.createImageInputStream(f);

if (imagein == null) {

return "application/octet-stream";

}

Iterator<ImageReader> it = ImageIO.getImageReaders(imagein);

if (!it.hasNext()) {

imagein.close();

return "application/octet-stream";

}

imagein.close();

return "image/" + it.next().getFormatName().toLowerCase();//将FormatName返回的值转换成小写，默认为大写

}

//把文件转换成字节数组

private byte[] getBytes(File f) throws Exception {

FileInputStream in = new FileInputStream(f);

ByteArrayOutputStream out = new ByteArrayOutputStream();

byte[] b = new byte[1024];

int n;

while ((n = in.read(b)) != -1) {

out.write(b, 0, n);

}

in.close();

return out.toByteArray();

}

//添加结尾数据

private void paramsEnd() throws Exception {

ds.writeBytes("--" + boundary + "--" + "\r\n");

ds.writeBytes("\r\n");

}

// 对包含中文的字符串进行转码，此为UTF-8。服务器那边要进行一次解码

private String encode(String value) throws Exception{

return URLEncoder.encode(value, "UTF-8");

}

public static void main(String[] args) throws Exception {

HttpPostUtil u = new HttpPostUtil("http://localhost:3000/up_load");

u.addFileParameter("img", new File(

"D:\\素材\\圆月.jpg"));

u.addTextParameter("text", "中文");

byte[] b = u.send();

String result = new String(b);

System.out.println(result);

}

}

后台使用ruby进行接收

ruby代码如下：

Ruby代码


require "cgi"

class UpLoadController < ApplicationController

protect_from_forgery :except=>:index

def index

img = params[:img]

if img.kind_of? String

logger.debug "img string : #{img}"

else

logger.debug "Content-Type:#{img.content_type}"

logger.debug "or:#{CGI.unescape(img.original_filename)}"

end

text = params[:text]

logger.debug "text:#{CGI.unescape(text)}"

render :text=>"OK"

end

end

日志输入如下：

Content-Type:image/jpeg

or:圆月.jpg

text:中文

如果不把中文转成UTF-8的格式进行传输，则后台显示中文乱码。

同样，如果其他参数包含中文，则也应当先转码。

当然，具体什么编码要和后台接收的编码一致。

另外附上c#的代码，因为对c#不太熟悉，但代码测试基本可以实现了。

C#代码


using System;

using System.Drawing;

using System.IO;

using System.Net;

using System.Text;

using System.Drawing.Imaging;

namespace MyThreading

{

class HttpPostUtil

{

string boundary = "------httpost123";

string url;

byte[] bs= new byte[0];

Encoding encoder = Encoding.UTF8;

public HttpPostUtil(string url)

{

this.url = url;

}

public byte[] Send()

{

WebClient myWebClient = new WebClient();

myWebClient.Headers.Add("Content-Type", "multipart/form-data; boundary=" + boundary);

EndData();

return myWebClient.UploadData(url,bs);

}

public void ClearData()

{

Array.Clear(bs, 0, bs.Length);

}

public void AddTextParameter(string name, string value)

{

StringBuilder s = new StringBuilder();

s.Append("--").Append(boundary).Append("\r\n");

s.Append("Content-Disposition: form-data; name=\"" + name + "\"\r\n");

s.Append("\r\n");

s.Append(value).Append("\r\n");

AppendString(s.ToString());

}

public void AddFileParameter(string name, FileInfo file)

{

StringBuilder s = new StringBuilder();

s.Append("--").Append(boundary).Append("\r\n");

s.Append("Content-Disposition: form-data; name=\"" + name + "\"; filename=\"" + file.Name + "\"\r\n");

s.Append("Content-Type: " + GetContentType(file) + "\r\n");

s.Append("\r\n");

AppendString(s.ToString());

AppendBytes(GetFileBytes(file));

AppendString("\r\n");

}

byte[] GetFileBytes(FileInfo f)

{

FileStream fs = new FileStream(f.FullName, FileMode.Open);

BinaryReader br = new BinaryReader(fs);

byte[] b = br.ReadBytes((int)f.Length);

br.Close();

fs.Close();

return b;

}

string GetContentType(FileInfo f)

{

// return "application/octet-stream"; //取消注释此行，则不再区分是否为图片

System.Drawing.Image image = null;

FileStream fs = new FileStream(f.FullName, FileMode.Open);

try

{

image = System.Drawing.Image.FromStream(fs);

}

catch (ArgumentException)

{

// 文件无法被解析为一个图片

return "application/octet-stream";

}

finally

{

fs.Close();

}

return GetFormat(image.RawFormat);

}

string GetFormat(ImageFormat imf)

{

if (ImageFormat.Bmp.Equals(imf))

{

return "image/bmp";

}

if (ImageFormat.Jpeg.Equals(imf))

{

return "image/jpeg";

}

if (ImageFormat.Png.Equals(imf))

{

return "image/png";

}

return "application/octet-stream";

}

void AppendBytes(byte[] bytes)

{

byte[] newByte = new byte[bs.Length + bytes.Length];

Array.Copy(bs, 0, newByte, 0, bs.Length);

Array.Copy(bytes, 0, newByte, bs.Length, bytes.Length);

bs = newByte;

}

void AppendString(string value)

{

byte[] bytes = Encoding.UTF8.GetBytes(value);

AppendBytes(bytes);

}

void EndData()

{

StringBuilder s = new StringBuilder();

s.Append("--").Append(boundary).Append("--\r\n");

s.Append("\r\n");

AppendString(s.ToString());

}

}

}

在我本机测试，中文没有出现乱码。

c#调用方法：

C#代码


string url = "http://localhost:3000/up_load";

string imgPath = @"D:\素材\圆月.jpg";

HttpPostUtil hp = new HttpPostUtil(url);

hp.AddTextParameter("text","中文");

hp.AddFileParameter("img",new FileInfo(imgPath));

byte[] b = hp.Send();

Console.WriteLine(Encoding.UTF8.GetString(b));