<pre name="code" class="java"><span style="font-size:24px;"><span style="font-size:24px;">package com.melody.clf;
import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
/**
* 开始位置:id*size
* 结束位置:(id + 1)* size -1
* 最后一个线程的结束位置:length -1
* @author Administrator
*
*/
public class Main {
static String path = "http://192.168.119.14/ep.exe";
static int threadCount = 3; //定义线程数量
public static void main(String[] args) {
//发送http请求,拿到目标文件长度
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setReadTimeout(8000);
conn.setConnectTimeout(8000);
if(conn.getResponseCode() == 200){
//获取长度
int length = conn.getContentLength();
//创建临时文件 先占用硬盘空间
// File(路径,文件名) 路径不写默认存到项目的根目录
File file = new File(getNameFrompath(path));
//随机存储,创建临时文件
/**
* mode :
* r:只读
* rw:读写,文件不存在,则创建
* rws:读写,对文件内容或者元数据的每个更新都同步写入到底层存储设备
* rwd:读写,对文件内容的每个更新都同步写入到底层存储设备
*/
RandomAccessFile raf = new RandomAccessFile(file, "rwd");
//设置临时文件大小与目标文件一直
raf.setLength(length);
raf.close();
//计算每个线程区间
int size = length / threadCount;
//计算每个线程开始的位置和结束的位置
for(int id = 0; id < threadCount; id++){
int startIndex = id * size; //开始位置
int endIndex = (id+1)*size-1; //结束位置
if(id == threadCount -1){ //最后一个线程结束的位置
endIndex = length -1;
}
System.out.println("线程" + id +"下载的区间" + startIndex + "~" + endIndex);
new DownLoad(id, startIndex, endIndex).start();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
// 截取字段获取文件名
public static String getNameFrompath(String path){
//搜索最后一个斜杠
int index = path.lastIndexOf("/");
// 斜杠前后开始截取
return path.substring(index + 1);
}
public static class DownLoad extends Thread{
int threadId; //线程ID
int startIndex; //开始区间
int endIndex; //结束区间
public DownLoad(int threadId, int startIndex, int endIndex) {
super();
this.threadId = threadId;
this.startIndex = startIndex;
this.endIndex = endIndex;
}
public void run() {
//发送http请求,请求要下载的数据
try {
URL url = new URL(Main.path);
HttpURLConnection conn =(HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setReadTimeout(8000);
conn.setReadTimeout(8000);
//设置请求数据区间 从startIndex到endIndex之间
conn.setRequestProperty("Range", "bytes=" + startIndex +"-" + endIndex);
//请求部分数据成功的响应吗是206
if(conn.getResponseCode() == 206){
InputStream is = conn.getInputStream();
//开始读取数据
byte[] b = new byte[1024];
int len = 0;
//当前线程下载的总进度
int total = 0;
//读取临时文件里的数据
File file = new File(getNameFrompath(path));
RandomAccessFile raf = new RandomAccessFile(file, "rwd");
//设置写入文件的开始位置
raf.seek(startIndex);
//没读取1K就把这1K写到输出流里面
while((len = is.read(b)) != -1){
raf.write(b,0,len);
total +=len;
System.out.println("线程" + threadId +"下载了:"+total);
}
raf.close();
System.out.println("线程" + threadId +"下载完毕"+"-------------------------");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
</span>
</span>
java版多线程下载
最新推荐文章于 2017-03-15 21:05:23 发布