DownloadURLFile网络文件下载

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.URL;

import java.nio.MappedByteBuffer;

import java.nio.channels.FileChannel;

import javax.servlet.http.HttpServletResponse;

import com.hurong.credit.util.RsaHelper;

public class DownloadURLFile {

private static final DownloadURLFile downloadURLFile = new DownloadURLFile();

public static DownloadURLFile getInstance()

{

return downloadURLFile;

}

/**

* 执行下载

* @param rfPosit 远程文件开始下载位置

*/

public static void start(long rfPosit,URL remoteFile,File storeFile){

HttpURLConnection httpConn = null;

InputStream httpIn = null;

try{

System.out.println("打开HttpURLConnection.");

httpConn = (HttpURLConnection)remoteFile.openConnection();

httpConn.setRequestProperty("User-Agent","NetFox");

httpConn.setRequestProperty("RANGE","bytes="+rfPosit+"-");

System.out.println("得到HttpInputStream.");

httpIn = httpConn.getInputStream();

writeFile(httpIn,storeFile);

System.out.println("关闭HttpURLConnection.");

httpConn.disconnect();

}catch(Exception ex){

ex.printStackTrace();

}

}

/**

* 从HttpInputStream中读数据并写到本地文件中

* @param in HttpInputStream

*/

private static void writeFile(InputStream in,File storeFile){

RandomAccessFile fileOut = null;

int buffer_len = 512;

byte[] buffer = new byte[buffer_len];

int readLen = 0;

try{

System.out.println("写本地文件.");

fileOut = new RandomAccessFile(storeFile, "rw");

fileOut.seek(fileOut.length());

while(-1 != (readLen = in.read(buffer, 0, buffer_len))){

fileOut.write(buffer, 0, readLen);

}

fileOut.close();

}catch(Exception ex){

ex.printStackTrace();

}

}

/**

* 大文件下载

* @param path

* @param response

*/

public static void downLoad(String path, HttpServletResponse response){

final int BUFFER_SIZE = 0x3000;// 缓冲区大小为3M

boolean isInline = false; // 是否允许直接在浏览器内打开

OutputStream toClient = null;

File f=new File(path);

/**

*

* map(FileChannel.MapMode mode,long position, long size)

*

* mode - 根据是按只读、读取/写入或专用（写入时拷贝）来映射文件，分别为 FileChannel.MapMode 类中所定义的

* READ_ONLY、READ_WRITE 或 PRIVATE 之一

*

* position - 文件中的位置，映射区域从此位置开始；必须为非负数

*

* size - 要映射的区域大小；必须为非负数且不大于 Integer.MAX_VALUE

*

* 所以若想读取文件后半部分内容，如例子所写；若想读取文本后1/8内容，需要这样写map(FileChannel.MapMode.READ_ONLY,

* f.length()*7/8,f.length()/8)

*

* 想读取文件所有内容，需要这样写map(FileChannel.MapMode.READ_ONLY, 0,f.length())

*

*/

MappedByteBuffer inputBuffer=null;

long start = 0;

try {

String filename = new String(f.getName().getBytes(), "ISO8859-1");

String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();

response.reset();

String inlineType = isInline ? "inline" : "attachment"; // 是否内联附件

response.setHeader("content-disposition", "attachment;filename=\""+ filename + "\"");

//response.setContentType("application/pdf");

inputBuffer = new RandomAccessFile(f, "r").getChannel().map(FileChannel.MapMode.READ_ONLY, 0,f.length());

　　　　　　　byte[] dst = new byte[BUFFER_SIZE];// 每次读出3M的内容

start = System.currentTimeMillis();

// if(inputBuffer.capacity()>BUFFER_SIZE){

for (int offset = 0; offset < inputBuffer.capacity(); offset += BUFFER_SIZE) {

if (inputBuffer.capacity() - offset >= BUFFER_SIZE) {

for (int i = 0; i < BUFFER_SIZE; i++)

dst[i] = inputBuffer.get(offset + i);

} else {

for (int i = 0; i < inputBuffer.capacity() - offset; i++)

dst[i] = inputBuffer.get(offset + i);

}

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

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

toClient.write(dst);

}

/*}else{

//dst[0]=inputBuffer;

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

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

toClient.write(inputBuffer.get(0));

}*/

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

} finally {

try {

if (null != toClient) {

toClient.close();

toClient.flush();

}

} catch (Exception e) {

e.printStackTrace();

}

}

long end = System.currentTimeMillis();

System.out.println("读取文件文件内容花费：" + (end - start) + "毫秒");

}

}