blocks|key|877363|text|查看this+thread+which+has+a+problem+similar+to+yours。如果wget正在工作，那么服务器显然支持恢复下载。看起来您没有设置上面链接的已接受答案中提到的If-Range标头。即。添加：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|877364|//+Initial+download.
String+lastModified+=+connection.getHeaderField("Last-Modified");

//+...

//+Resume+download.
connection.setRequestProperty("If-Range",+lastModified);+|code-block|syntax|javascript|877365|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/3428102/how-to-resume-an-interrupted-download-part-2^0|2Q|8|2|1C|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

Check out <a href="https://stackoverflow.com/questions/3428102/how-to-resume-an-interrupted-download-part-2">this thread which has a problem similar to yours</a>. If wget is working, then the server clearly supports resuming downloads. It looks like you're not setting the <code>If-Range</code> header as mentioned in the accepted answer of the above link. ie. add:

<pre><code>// Initial download.
String lastModified = connection.getHeaderField("Last-Modified");

// ...

// Resume download.
connection.setRequestProperty("If-Range", lastModified); 
</code></pre>

blocks|key|660317|text|+HttpURLConnection+connection+=+(HttpURLConnection)+url.openConnection();
++++if(ISSUE_DOWNLOAD_STATUS.intValue()==ECMConstant.ECM_DOWNLOADING){
++++++++File+file=new+File(DESTINATION_PATH);
++++++++if(file.exists()){
+++++++++++++downloaded+=+(int)+file.length();
+++++++++++++connection.setRequestProperty("Range",+"bytes="%2B(file.length())%2B"-");
++++++++}
++++}else{
++++++++connection.setRequestProperty("Range",+"bytes="+%2B+downloaded+%2B+"-");
++++}
++++connection.setDoInput(true);
++++connection.setDoOutput(true);
++++progressBar.setMax(connection.getContentLength());
+++++in+=+new+BufferedInputStream(connection.getInputStream());
+++++fos=(downloaded==0)?+new+FileOutputStream(DESTINATION_PATH):+new+FileOutputStream(DESTINATION_PATH,true);
+++++bout+=+new+BufferedOutputStream(fos,+1024);
++++byte[]+data+=+new+byte[1024];
++++int+x+=+0;
++++while+((x+=+in.read(data,+0,+1024))+>=+0)+{
++++++++bout.write(data,+0,+x);
+++++++++downloaded+%2B=+x;
+++++++++progressBar.setProgress(downloaded);
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|660318|这不是我的代码，但它可以工作。|unstyled|660319|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code> HttpURLConnection connection = (HttpURLConnection) url.openConnection();
 if(ISSUE_DOWNLOAD_STATUS.intValue()==ECMConstant.ECM_DOWNLOADING){
 File file=new File(DESTINATION_PATH);
 if(file.exists()){
 downloaded = (int) file.length();
 connection.setRequestProperty("Range", "bytes="+(file.length())+"-");
 }
 }else{
 connection.setRequestProperty("Range", "bytes=" + downloaded + "-");
 }
 connection.setDoInput(true);
 connection.setDoOutput(true);
 progressBar.setMax(connection.getContentLength());
 in = new BufferedInputStream(connection.getInputStream());
 fos=(downloaded==0)? new FileOutputStream(DESTINATION_PATH): new FileOutputStream(DESTINATION_PATH,true);
 bout = new BufferedOutputStream(fos, 1024);
 byte[] data = new byte[1024];
 int x = 0;
 while ((x = in.read(data, 0, 1024)) &gt;= 0) {
 bout.write(data, 0, x);
 downloaded += x;
 progressBar.setProgress(downloaded);
 }
</code></pre>

This is not my code, but it works.

blocks|key|877517|text|我猜您面临的问题是在url.openConnection()之后调用url.openStream()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|877518|url.openStream()等同于url.openConnection().getInputStream()。因此，您将请求url两次。特别是第二次，它没有指定range属性。因此，下载总是从头开始。|877519|您应该用connection.getInputStream()替换url.openStream()。|877520|entityMap^0|A|K|Y|G|0|0|G|J|11|0|4|R|X|G|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|K|$]]

I guess the problem you are facing is calling <code>url.openStream()</code> after <code>url.openConnection()</code>.

<code>url.openStream()</code> is equivalent to <code>url.openConnection().getInputStream()</code>. Hence, you are requesting the url twice. Particularly the second time, it is not specifying the range property. Therefore download always starts at the beginning.

You should replace <code>url.openStream()</code> with <code>connection.getInputStream()</code>.

blocks|key|660440|text|因为这个问题的标签是Android:你试过使用DownloadManager吗？它能很好地为你处理所有这些事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|660441|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/app/DownloadManager.html?^0|N|F|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Since the question is tagged with Android:
Have you tried using <a href="http://developer.android.com/reference/android/app/DownloadManager.html?" rel="nofollow">DownloadManager</a>.
It handles all this stuff nicely for you.

blocks|key|660479|text|这个怎么样？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|660480|public+static+void+download(DownloadObject+object)+throws+IOException{
++++String+downloadUrl+=+object.getDownloadUrl();
++++String+downloadPath+=+object.getDownloadPath();
++++long+downloadedLength+=+0;

++++File+file+=+new+File(downloadPath);
++++URL+url+=+new+URL(downloadUrl);

++++BufferedInputStream+inputStream+=+null;
++++BufferedOutputStream+outputStream+=+null;

++++URLConnection+connection+=+url.openConnection();

++++if(file.exists()){
++++++++downloadedLength+=+file.length();
++++++++connection.setRequestProperty("Range",+"bytes="+%2B+downloadedLength+%2B+"-");
++++++++outputStream+=+new+BufferedOutputStream(new+FileOutputStream(file,+true));

++++}else{
++++++++outputStream+=+new+BufferedOutputStream(new+FileOutputStream(file));

++++}

++++connection.connect();

++++inputStream+=+new+BufferedInputStream(connection.getInputStream());


++++byte[]+buffer+=+new+byte[1024*8];
++++int+byteCount;

++++while+((byteCount+=+inputStream.read(buffer))+!=+-1){
++++++++outputStream.write(buffer,+0,+byteCount);
++++++++break;

++++}

++++inputStream.close();
++++outputStream.flush();
++++outputStream.close();

}|code-block|syntax|javascript|660481|使用break;测试代码。;)|offset|length|style|CODE|660482|entityMap^0|0|0|2|6|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

How about this?

<pre><code>public static void download(DownloadObject object) throws IOException{
 String downloadUrl = object.getDownloadUrl();
 String downloadPath = object.getDownloadPath();
 long downloadedLength = 0;

 File file = new File(downloadPath);
 URL url = new URL(downloadUrl);

 BufferedInputStream inputStream = null;
 BufferedOutputStream outputStream = null;

 URLConnection connection = url.openConnection();

 if(file.exists()){
 downloadedLength = file.length();
 connection.setRequestProperty("Range", "bytes=" + downloadedLength + "-");
 outputStream = new BufferedOutputStream(new FileOutputStream(file, true));

 }else{
 outputStream = new BufferedOutputStream(new FileOutputStream(file));

 }

 connection.connect();

 inputStream = new BufferedInputStream(connection.getInputStream());


 byte[] buffer = new byte[1024*8];
 int byteCount;

 while ((byteCount = inputStream.read(buffer)) != -1){
 outputStream.write(buffer, 0, byteCount);
 break;

 }

 inputStream.close();
 outputStream.flush();
 outputStream.close();

}
</code></pre>

Used <code>break;</code> to test the code.. ;)

blocks|key|877682|text|这是我用来下载文件的块，更新用户界面的进度。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|877683|/*
+*+@param+callback+=+To+update+the+UI+with+appropriate+action
+*+@param+fileName+=+Name+of+the+file+by+which+downloaded+file+will+be+saved.
+*+@param+downloadURL+=+File+downloading+URL
+*+@param+filePath+=+Path+where+file+will+be+saved
+*+@param+object+=+Any+object+you+want+in+return+after+download+is+completed+to+do+certain+operations+like+insert+in+DB+or+show+toast
+*/

public+void+startDownload(final+IDownloadCallback+callback,+String+fileName,+String+downloadURL,+String+filePath,+Object+object)+{
++++callback.onPreExecute();+//+Callback+to+tell+that+the+downloading+is+going+to+start
++++int+count+=+0;
++++File+outputFile+=+null;+//+Path+where+file+will+be+downloaded
++++try+{
++++++++File+file+=+new+File(filePath);
++++++++file.mkdirs();
++++++++long+range+=+0;
++++++++outputFile+=+new+File(file,+fileName);
++++++++/**
+++++++++*+Check+whether+the+file+exists+or+not
+++++++++*+If+file+doesn't+exists+then+create+the+new+file+and+range+will+be+zero.
+++++++++*+But+if+file+exists+then+get+the+length+of+file+which+will+be+the+starting+range,
+++++++++*+from+where+the+file+will+be+downloaded
+++++++++*/
++++++++if+(!outputFile.exists())+{
++++++++++++outputFile.createNewFile();
++++++++++++range+=+0;
++++++++}+else+{
++++++++++++range+=+outputFile.length();
++++++++}
++++++++//Open+the+Connection
++++++++URL+url+=+new+URL(downloadURL);
++++++++URLConnection+con+=+url.openConnection();
++++++++//+Set+the+range+parameter+in+header+and+give+the+range+from+where+you+want+to+start+the+downloading
++++++++con.setRequestProperty("Range",+"bytes="+%2B+range+%2B+"-");
++++++++/**
+++++++++*+The+total+length+of+file+will+be+the+total+content+length+given+by+the+server+%2B+range.
+++++++++*+Example:+Suppose+you+have+a+file+whose+size+is+1MB+and+you+had+already+downloaded+500KB+of+it.
+++++++++*+Then+you+will+pass+in+Header+as+"Range":"bytes=500000".
+++++++++*+Now+the+con.getContentLength()+will+be+500KB+and+range+will+be+500KB.
+++++++++*+So+by+adding+the+two+you+will+get+the+total+length+of+file+which+will+be+1+MB
+++++++++*/
++++++++final+long+lenghtOfFile+=+(int)+con.getContentLength()+%2B+range;

++++++++FileOutputStream+fileOutputStream+=+new+FileOutputStream(outputFile,+true);
++++++++InputStream+inputStream+=+con.getInputStream();

++++++++byte[]+buffer+=+new+byte[1024];

++++++++long+total+=+range;
++++++++/**
+++++++++*+Download+the+save+the+content+into+file
+++++++++*/
++++++++while+((count+=+inputStream.read(buffer))+!=+-1)+{
++++++++++++total+%2B=+count;
++++++++++++int+progress+=+(int)+(total+*+100+/+lenghtOfFile);
++++++++++++EntityDownloadProgress+entityDownloadProgress+=+new+EntityDownloadProgress();
++++++++++++entityDownloadProgress.setProgress(progress);
++++++++++++entityDownloadProgress.setDownloadedSize(total);
++++++++++++entityDownloadProgress.setFileSize(lenghtOfFile);
++++++++++++callback.showProgress(entityDownloadProgress);
++++++++++++fileOutputStream.write(buffer,+0,+count);
++++++++}
++++++++//Close+the+outputstream
++++++++fileOutputStream.close();
++++++++//+Disconnect+the+Connection
++++++++if+(con+instanceof+HttpsURLConnection)+{
++++++++++++((HttpsURLConnection)+con).disconnect();
++++++++}+else+if+(con+instanceof+HttpURLConnection)+{
++++++++++++((HttpURLConnection)+con).disconnect();
++++++++}
++++++++inputStream.close();
++++++++/**
+++++++++*+If+file+size+is+equal+then+return+callback+as+success+with+downlaoded+filepath+and+the+object
+++++++++*+else+return+failure
+++++++++*/
++++++++if+(lenghtOfFile+==+outputFile.length())+{
++++++++++++callback.onSuccess(outputFile.getAbsolutePath(),+object);
++++++++}+else+{
++++++++++++callback.onFailure(object);
++++++++}
++++}+catch+(Exception+e)+{
++++++++e.printStackTrace();
++++++++callback.onFailure(object);
++++}
}|code-block|syntax|javascript|877684|接口IDownloadCallback+{|877685|++++void+onPreExecute();+//+Callback+to+tell+that+the+downloading+is+going+to+start
++++void+onFailure(Object+o);+//+Failed+to+download+file
++++void+onSuccess(String+path,+Object+o);+//+Downloaded+file+successfully+with+downloaded+path
++++void+showProgress(EntityDownloadProgress+entityDownloadProgress);+//+Show+progress
}|877686|公共类EntityDownloadProgress+{|877687|++++int+progress;+//+range+from+1-100
++++long+fileSize;//+Total+size+of+file+to+be+downlaoded
++++long+downloadedSize;+//+Size+of+the+downlaoded+file

++++public+void+setProgress(int+progress)+{this.progress+=+progress;}

++++public+void+setFileSize(long+fileSize)+{this.fileSize+=+fileSize;}

++++public+void+setDownloadedSize(long+downloadedSize)+{this.downloadedSize+=+downloadedSize;}
}|877688|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

This is what I am using to download the file in chunk Updating the UI with progress.
<pre><code>/*
 * @param callback = To update the UI with appropriate action
 * @param fileName = Name of the file by which downloaded file will be saved.
 * @param downloadURL = File downloading URL
 * @param filePath = Path where file will be saved
 * @param object = Any object you want in return after download is completed to do certain operations like insert in DB or show toast
 */

public void startDownload(final IDownloadCallback callback, String fileName, String downloadURL, String filePath, Object object) {
 callback.onPreExecute(); // Callback to tell that the downloading is going to start
 int count = 0;
 File outputFile = null; // Path where file will be downloaded
 try {
 File file = new File(filePath);
 file.mkdirs();
 long range = 0;
 outputFile = new File(file, fileName);
 /**
 * Check whether the file exists or not
 * If file doesn't exists then create the new file and range will be zero.
 * But if file exists then get the length of file which will be the starting range,
 * from where the file will be downloaded
 */
 if (!outputFile.exists()) {
 outputFile.createNewFile();
 range = 0;
 } else {
 range = outputFile.length();
 }
 //Open the Connection
 URL url = new URL(downloadURL);
 URLConnection con = url.openConnection();
 // Set the range parameter in header and give the range from where you want to start the downloading
 con.setRequestProperty(&quot;Range&quot;, &quot;bytes=&quot; + range + &quot;-&quot;);
 /**
 * The total length of file will be the total content length given by the server + range.
 * Example: Suppose you have a file whose size is 1MB and you had already downloaded 500KB of it.
 * Then you will pass in Header as &quot;Range&quot;:&quot;bytes=500000&quot;.
 * Now the con.getContentLength() will be 500KB and range will be 500KB.
 * So by adding the two you will get the total length of file which will be 1 MB
 */
 final long lenghtOfFile = (int) con.getContentLength() + range;

 FileOutputStream fileOutputStream = new FileOutputStream(outputFile, true);
 InputStream inputStream = con.getInputStream();

 byte[] buffer = new byte[1024];

 long total = range;
 /**
 * Download the save the content into file
 */
 while ((count = inputStream.read(buffer)) != -1) {
 total += count;
 int progress = (int) (total * 100 / lenghtOfFile);
 EntityDownloadProgress entityDownloadProgress = new EntityDownloadProgress();
 entityDownloadProgress.setProgress(progress);
 entityDownloadProgress.setDownloadedSize(total);
 entityDownloadProgress.setFileSize(lenghtOfFile);
 callback.showProgress(entityDownloadProgress);
 fileOutputStream.write(buffer, 0, count);
 }
 //Close the outputstream
 fileOutputStream.close();
 // Disconnect the Connection
 if (con instanceof HttpsURLConnection) {
 ((HttpsURLConnection) con).disconnect();
 } else if (con instanceof HttpURLConnection) {
 ((HttpURLConnection) con).disconnect();
 }
 inputStream.close();
 /**
 * If file size is equal then return callback as success with downlaoded filepath and the object
 * else return failure
 */
 if (lenghtOfFile == outputFile.length()) {
 callback.onSuccess(outputFile.getAbsolutePath(), object);
 } else {
 callback.onFailure(object);
 }
 } catch (Exception e) {
 e.printStackTrace();
 callback.onFailure(object);
 }
}
</code></pre>
interface IDownloadCallback {
<pre><code> void onPreExecute(); // Callback to tell that the downloading is going to start
 void onFailure(Object o); // Failed to download file
 void onSuccess(String path, Object o); // Downloaded file successfully with downloaded path
 void showProgress(EntityDownloadProgress entityDownloadProgress); // Show progress
}
</code></pre>
public class EntityDownloadProgress {
<pre><code> int progress; // range from 1-100
 long fileSize;// Total size of file to be downlaoded
 long downloadedSize; // Size of the downlaoded file

 public void setProgress(int progress) {this.progress = progress;}

 public void setFileSize(long fileSize) {this.fileSize = fileSize;}

 public void setDownloadedSize(long downloadedSize) {this.downloadedSize = downloadedSize;}
}
</code></pre>

<pre><code>URL url = new URL("http://download.thinkbroadband.com/20MB.zip");

URLConnection connection = url.openConnection();
File fileThatExists = new File(path); 
OutputStream output = new FileOutputStream(path, true);
connection.setRequestProperty("Range", "bytes=" + fileThatExists.length() + "-");

connection.connect();

int lenghtOfFile = connection.getContentLength();

InputStream input = new BufferedInputStream(url.openStream());
byte data[] = new byte[1024];

long total = 0;

while ((count = input.read(data)) != -1) {
 total += count;

 output.write(data, 0 , count);
}
</code></pre>

in this code I try to resume download. Target file is 20MB. But when I stop download on 10mb, then contunue, I get file with filesize 30MB. It seems that it continue writing to file, but cant partly download from server. Wget -c works great with this file. How can I resume file download?

Resume http file download in java

服务器

Android

URL url = new URL("http://download.thinkbroadband.com/20MB.zip");URLConnection connection = url.openConnection();File fileThatExists = new File(path); OutputStr...

问在java中恢复http文件下载
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