java 下載功能

import java.io.File;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.ProtocolException;import java.net.URI;import java.net.URL;import java.util.Random;/** * * 實(shí)現(xiàn)了下載的功能*/ public class SimpleTh { public static void main(String[] args){ // TODO Auto-generated method stub //String path = "倩女幽魂.mp3";//MP3下載的地址 String path =""; try { new SimpleTh().download(path, 3); //對象調(diào)用下載的方法 } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static String getFilename(String path){//獲得文件的名字 return path.substring(path.lastIndexOf('/')+1); } public void download(String path,int threadsize) throws Exception//下載的方法 {//參數(shù) 下載地址，線程數(shù)量 URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection)url.openConnection();//獲取HttpURLConnection對象 conn.setRequestMethod("GET");//設(shè)置請求格式，這里是GET格式 conn.setReadTimeout(5*1000);// int filelength = conn.getContentLength();//獲取要下載文件的長度 String filename = getFilename(path); File saveFile = new File(filename); RandomAccessFile accessFile = new RandomAccessFile(saveFile, "rwd"); accessFile.setLength(filelength); accessFile.close(); int block = filelength%threadsize ==0?filelength/threadsize:filelength/threadsize+1; for(int threadid = 0;threadid=threadsize;threadid++){ new DownloadThread(url,saveFile,block,threadid).start(); } } private final class DownloadThread extends Thread{ private URL url; private File saveFile; private int block;//每條線程下載的長度 private int threadid;//線程id public DownloadThread(URL url,File saveFile,int block,int threadid){ this.url = url; this.saveFile= saveFile; this.block = block; this.threadid = threadid; } @Override public void run() { //計(jì)算開始位置的公式：線程id*每條線程下載的數(shù)據(jù)長度=？ //計(jì)算結(jié)束位置的公式：（線程id+1）*每條線程下載數(shù)據(jù)長度-1=？ int startposition = threadid*block; int endposition = (threadid+1)*block-1; try { try { RandomAccessFile accessFile = new RandomAccessFile(saveFile, "rwd"); accessFile.seek(startposition);//設(shè)置從什么位置寫入數(shù)據(jù) HttpURLConnection conn = (HttpURLConnection)url.openConnection(); conn.setRequestMethod("GET"); conn.setReadTimeout(5*1000); conn.setRequestProperty("Range","bytes= "+startposition+"-"+endposition); InputStream inStream = conn.getInputStream(); byte[]buffer = new byte[1024]; int len = 0; while((len = inStream.read(buffer))!=-1){ accessFile.write(buffer, 0, len); } inStream.close(); accessFile.close(); System.out.println("線程id："+threadid+"下載完成"); } catch (FileNotFoundException e) { e.printStackTrace(); } } catch (IOException e) { e.printStackTrace(); } } }}

讓客戶滿意是我們工作的目標(biāo)，不斷超越客戶的期望值來自于我們對這個(gè)行業(yè)的熱愛。我們立志把好的技術(shù)通過有效、簡單的方式提供給客戶，將通過不懈努力成為客戶在信息化領(lǐng)域值得信任、有價(jià)值的長期合作伙伴，公司提供的服務(wù)項(xiàng)目有：域名注冊、雅安服務(wù)器托管、營銷軟件、網(wǎng)站建設(shè)、秭歸網(wǎng)站維護(hù)、網(wǎng)站推廣。

參考一下這個(gè)代碼。

java中怎么實(shí)現(xiàn)下載功能，最好能有代碼

private File uploadify;

private String uploadifyFileName;

public String uploadFile1() throws Exception {

String extName = "";// 擴(kuò)展名

String newFileName = "";// 新文件名

String nowTime = df.format(new Date());// 當(dāng)前時(shí)間

String random = "-" + (Math.round(Math.random() * 9000) + 1000);// 隨機(jī)函數(shù)

String path = "uploads/" + nowTime.substring(0, 6) + "/"

+ nowTime.substring(0, 8) + "/";// 保存路徑

String savePath = ServletActionContext.getServletContext().getRealPath(

"");

savePath = savePath.replace("\\", "/");

if (!savePath.substring(savePath.length()).equals("/"))

savePath = savePath + "/";

savePath = savePath + path;

// 獲取擴(kuò)展名

if (uploadifyFileName.lastIndexOf(".") = 0) {

extName = uploadifyFileName.substring(uploadifyFileName

.lastIndexOf("."));

}

newFileName = uploadifyFileName.substring(0,

uploadifyFileName.lastIndexOf("."))

+ nowTime.substring(8) + random + extName;

File file = new File(savePath);

if (!file.exists())

file.mkdirs();

uploadify.renameTo(new File(savePath + newFileName));

/*

* HttpServletResponse response = ServletActionContext.getResponse();

* response.setCharacterEncoding("utf-8");

* response.getWriter().print(uploadifyFileName+"上傳成功");

*/

String ctx = Struts2Utils.getRequest().getContextPath();

Struts2Utils.renderText(ctx + "/" + path + newFileName);

Wenjdetail detail = new Wenjdetail();

String pt = path + newFileName;

detail.setName(uploadifyFileName);

detail.setUrl(pt);

wenjdetailManager.saveWenjdetail(detail);

HttpServletResponse response = ServletActionContext.getResponse();

response.setCharacterEncoding("utf-8");

response.getWriter().print("," + detail.getId());

return null; // 這里不需要頁面轉(zhuǎn)向，所以返回空就可以了

}

有關(guān)java實(shí)現(xiàn)下載的功能

樓主得在后臺(tái)的控制器中用reponse的輸出流轉(zhuǎn)化一下，我給你個(gè)例子。

InputStream?fis?=?new?BufferedInputStream(new?FileInputStream(filePath));

byte[]?buffer?=?new?byte[fis.available()];

fis.read(buffer);

fis.close();

response.reset();

response.addHeader("Content-Disposition",?"attachment;filename="?+?new?String(fileName.getBytes("gbk"),"ISO-8859-1"));

response.addHeader("Content-Length",?""?+?excelFile.length());

OutputStream?toClient?=?new?BufferedOutputStream(response.getOutputStream());

response.setContentType("application/octet-stream");

toClient.write(buffer);

toClient.flush();

toClient.close();

Struts1框架 用Java代碼實(shí)現(xiàn)文件下載 不彈出下載框 代碼：

下載代碼：

這里我使用的是SpringMVC，不過它在這里的唯一用途就是用來獲取ServletContext對象，這個(gè)對象的用途，下面實(shí)例中有說明

下載，需要用到兩個(gè)jar包：commons-fileupload.jar和commons-io.jar

Java代碼

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.context.ServletContextAware;

import javax.servlet.ServletContext;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServletResponse;

import java.io.*;

@Controller

public class FileController implements ServletContextAware{

//Spring這里是通過實(shí)現(xiàn)ServletContextAware接口來注入ServletContext對象

private ServletContext servletContext;

@RequestMapping("file/download")

public void fileDownload(HttpServletResponse response){

//獲取網(wǎng)站部署路徑(通過ServletContext對象)，用于確定下載文件位置，從而實(shí)現(xiàn)下載

String path = servletContext.getRealPath("/");

//1.設(shè)置文件ContentType類型，這樣設(shè)置，會(huì)自動(dòng)判斷下載文件類型

response.setContentType("multipart/form-data");

//2.設(shè)置文件頭：最后一個(gè)參數(shù)是設(shè)置下載文件名(假如我們叫a.pdf)

response.setHeader("Content-Disposition", "attachment;fileName="+"a.pdf");

ServletOutputStream out;

//通過文件路徑獲得File對象(假如此路徑中有一個(gè)download.pdf文件)

File file = new File(path + "download/" + "download.pdf");

try {

FileInputStream inputStream = new FileInputStream(file);

//3.通過response獲取ServletOutputStream對象(out)

out = response.getOutputStream();

int b = 0;

byte[] buffer = new byte[512];

while (b != -1){

b = inputStream.read(buffer);

//4.寫到輸出流(out)中

out.write(buffer,0,b);

}

inputStream.close();

out.close();

out.flush();

} catch (IOException e) {

e.printStackTrace();

}

}

@Override

public void setServletContext(ServletContext servletContext) {

this.servletContext = servletContext;

}

}

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