java下载功能代码,java 下载功能

java 下载功能

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;/** * * 实现了下载的功能*/ public class SimpleTh { public static void main(String[] args){ // TODO Auto-generated method stub //String path = "倩女幽魂.mp3";//MP3下载的地址 String path =""; try { new SimpleTh().download(path, 3); //对象调用下载的方法 } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static String getFilename(String path){//获得文件的名字 return path.substring(path.lastIndexOf('/')+1); } public void download(String path,int threadsize) throws Exception//下载的方法 {//参数 下载地址，线程数量 URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection)url.openConnection();//获取HttpURLConnection对象 conn.setRequestMethod("GET");//设置请求格式，这里是GET格式 conn.setReadTimeout(5*1000);// int filelength = conn.getContentLength();//获取要下载文件的长度 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;//每条线程下载的长度 private int threadid;//线程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() { //计算开始位置的公式：线程id*每条线程下载的数据长度=？ //计算结束位置的公式：（线程id+1）*每条线程下载数据长度-1=？ int startposition = threadid*block; int endposition = (threadid+1)*block-1; try { try { RandomAccessFile accessFile = new RandomAccessFile(saveFile, "rwd"); accessFile.seek(startposition);//设置从什么位置写入数据 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("线程id："+threadid+"下载完成"); } catch (FileNotFoundException e) { e.printStackTrace(); } } catch (IOException e) { e.printStackTrace(); } } }}

参考一下这个代码。

相关问答

Q1: java中怎么实现下载功能，最好能有代码

private File uploadify;

private String uploadifyFileName;

public String uploadFile1() throws Exception {

String extName = "";// 扩展名

String newFileName = "";// 新文件名

String nowTime = df.format(new Date());// 当前时间

String random = "-" + (Math.round(Math.random() * 9000) + 1000);// 随机函数

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

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

String savePath = ServletActionContext.getServletContext().getRealPath(

"");

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

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

savePath = savePath + "/";

savePath = savePath + path;

// 获取扩展名

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+"上传成功");

*/

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; // 这里不需要页面转向，所以返回空就可以了

}

Q2: 有关java实现下载的功能

楼主得在后台的控制器中用reponse的输出流转化一下，我给你个例子。

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();

Q3: Struts1框架 用Java代码实现文件下载 不弹出下载框 代码：

下载代码：

这里我使用的是SpringMVC，不过它在这里的唯一用途就是用来获取ServletContext对象，这个对象的用途，下面实例中有说明

下载，需要用到两个jar包：commons-fileupload.jar和commons-io.jar

Java代码

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这里是通过实现ServletContextAware接口来注入ServletContext对象

private ServletContext servletContext;

@RequestMapping("file/download")

public void fileDownload(HttpServletResponse response){

//获取网站部署路径(通过ServletContext对象)，用于确定下载文件位置，从而实现下载

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

//1.设置文件ContentType类型，这样设置，会自动判断下载文件类型

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

//2.设置文件头：最后一个参数是设置下载文件名(假如我们叫a.pdf)

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

ServletOutputStream out;

//通过文件路径获得File对象(假如此路径中有一个download.pdf文件)

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

try {

FileInputStream inputStream = new FileInputStream(file);

//3.通过response获取ServletOutputStream对象(out)

out = response.getOutputStream();

int b = 0;

byte[] buffer = new byte[512];

while (b != -1){

b = inputStream.read(buffer);

//4.写到输出流(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;

}

}