使用HttpURLConnection下载文件时经常会出现 java.io.FileNotFoundException文件找不到异常,下面介绍下解决办法
首先设置tomcat对get数据的编码:conf/server.xml
- <Connector port="8080" protocol="HTTP/1.1"
- connectionTimeout="20000"
- redirectPort="8443"
- <span style="color:#ff0000;"> URIEncoding="UTF-8"</span> />
其次对请求的文件名进行编码:
- import java.io.File;
- import java.io.IOException;
- import java.io.InputStream;
- import java.io.RandomAccessFile;
- import java.net.HttpURLConnection;
- import java.net.URL;
- import java.net.URLEncoder;
- /**
- * 多线程下载
- * @author bing
- *
- */
- public class OmbDownloadOfThreadsUtil {
- private String urlPath ; // 资源网络路径
- private String targetFilePath ; // 所下载文件的保存路径
- private int threadNum ; // 启用多少条线程进行下载
- // 用于下载线程对象集合
- private DownloadThread[] downloadThreads ;
- // 要下载文件的大小
- private int fileSize ;
- public OmbDownloadOfThreadsUtil(String urlPath, String targetFilePath,
- int threadNum) {
- this.urlPath = urlPath;
- this.targetFilePath = targetFilePath;
- this.threadNum = threadNum;
- downloadThreads = new DownloadThread[threadNum] ;
- }
- public void downloadFile() throws Exception{
- URL url = new URL(urlPath) ;
- HttpURLConnection conn = (HttpURLConnection) url.openConnection() ;
- conn.setConnectTimeout(4*1000) ;
- conn.setRequestMethod("GET") ;
- conn.setRequestProperty(
- "Accept",
- "image/gif, image/jpeg, image/pjpeg, image/pjpeg, " +
- "application/x-shockwave-flash, application/xaml+xml, " +
- "application/vnd.ms-xpsdocument, application/x-ms-xbap, " +
- "application/x-ms-application, application/vnd.ms-excel, " +
- "application/vnd.ms-powerpoint, application/msword, */*");
- conn.setRequestProperty("Accept-Language", "zh-CN");
- conn.setRequestProperty("Charset", "UTF-8");
- //设置浏览器类型和版本、操作系统,使用语言等信息
- conn.setRequestProperty(
- "User-Agent",
- "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; Trident/4.0; " +
- ".NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; " +
- ".NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
- //设置为长连接
- conn.setRequestProperty("Connection", "Keep-Alive");
- //得到要下载文件的大小
- fileSize = conn.getContentLength() ;
- System.out.println("fileSize:"+fileSize);
- //断开连接
- conn.disconnect() ;
- //计算每条线程需要下载的大小
- int preThreadDownloadSize = fileSize/threadNum+1 ;
- System.out.println("preThreadDownloadSize:"+preThreadDownloadSize);
- RandomAccessFile file = new RandomAccessFile(targetFilePath, "rw") ;
- file.setLength(fileSize) ;
- file.close() ;
- for (int i = 0; i < threadNum; i++) {
- // 计算每条线程下载的起始位置
- int startPos = i*preThreadDownloadSize+1 ;
- RandomAccessFile currentPart = new RandomAccessFile(targetFilePath, "rw") ;
- currentPart.seek(startPos) ;
- downloadThreads[i] = new DownloadThread(startPos,preThreadDownloadSize,currentPart) ;
- new Thread(downloadThreads[i]).start() ;
- }
- }
- /**
- * 获取下载的完成百分比
- * @return 完成的百分比
- */
- public double getCompleteRate() {
- // 统计多条线程已经下载的总大小
- int sumSize = 0;
- for (int i = 0; i < threadNum; i++) {
- sumSize += downloadThreads[i].hasReadLength;
- }
- // 返回已经完成的百分比
- return sumSize * 1.0 / fileSize;
- }
- /**
- * 用于下载的线程
- * @author bing
- *
- */
- private final class DownloadThread implements Runnable{
- private int startPos ;
- private int preThreadDownloadSize ;
- private RandomAccessFile currentPart ;
- //已下载长度
- private int hasReadLength ;
- public DownloadThread(int startPos, int preThreadDownloadSize,
- RandomAccessFile currentPart) {
- this.startPos = startPos;
- this.preThreadDownloadSize = preThreadDownloadSize;
- this.currentPart = currentPart;
- }
- @Override
- public void run() {
- InputStream inputStream = null ;
- try{
- URL url = new URL(urlPath) ;
- HttpURLConnection conn = (HttpURLConnection) url.openConnection() ;
- conn.setConnectTimeout(4*1000) ;
- conn.setRequestMethod("GET") ;
- conn.setRequestProperty(
- "Accept",
- "image/gif, image/jpeg, image/pjpeg, image/pjpeg, " +
- "application/x-shockwave-flash, application/xaml+xml, " +
- "application/vnd.ms-xpsdocument, application/x-ms-xbap, " +
- "application/x-ms-application, application/vnd.ms-excel, " +
- "application/vnd.ms-powerpoint, application/msword, */*");
- conn.setRequestProperty("Accept-Language", "zh-CN");
- conn.setRequestProperty("Charset", "UTF-8");
- inputStream = conn.getInputStream() ;
- inputStream.skip(startPos) ;//定位到开始位置
- byte[] buffer = new byte[1024] ;
- int temp = 0 ;
- while(hasReadLength<preThreadDownloadSize
- &&(temp=inputStream.read(buffer))!=-1){
- currentPart.write(buffer,0,temp) ;
- hasReadLength += temp ;
- }
- }catch(Exception e){
- e.printStackTrace() ;
- }finally{
- try {
- currentPart.close() ;
- } catch (Exception e) {
- e.printStackTrace();
- }
- try {
- inputStream.close() ;
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- }
- public static void main(String[] args) throws Exception {
- String songName = "许嵩 - 半城烟沙.mp3" ;
- songName = URLEncoder.encode(songName,"UTF-8") ;
- String urlPath = "http://172.16.2.50:8080/mp3/"+songName ;
- String targetDir = "E:"+File.separator+songName ;
- OmbDownloadOfThreadsUtil odtu = new OmbDownloadOfThreadsUtil(urlPath,targetDir, 6) ;
- odtu.downloadFile() ;
- }
- }
经过以上三步基本上问题已经解决,但如果的文件名含有空格的话还需一步:
URLs是不能包含空格的。URL encoding一般会使用“+”号去替换空格,但后台服务器(我的是Tomcat6.0)又不能把“+”还原为空格,所以导致文件找不到,解决办法:只需把“+”替换为“%20”
- public static void main(String[] args) throws Exception {
- String songName = "许嵩 - 半城烟沙.mp3" ;
- songName = URLEncoder.encode(songName,"UTF-8").replace("+", "%20") ;
- String urlPath = "http://172.16.2.50:8080/mp3/"+songName ;
- String targetDir = "E:"+File.separator+songName ;
- OmbDownloadOfThreadsUtil odtu = new OmbDownloadOfThreadsUtil(urlPath,targetDir, 6) ;
- odtu.downloadFile() ;
- }