/**
* 實作單線程的斷點下載下傳
*/
public class HttpDownloadSingle implements Runnable
{
// 響應狀态碼
private String responseCode;
// 響應頭資訊
private Map<String, String> headers = new HashMap<String, String>();
// 下載下傳事件處理類
private DownloadEvent event;
// 下載下傳檔案的url
private String url;
// 檔案儲存在本地的路徑
private String outFilePath;
// 緩沖區大小
private int bufferSize;
public HttpDownloadSingle(DownloadEvent event, String url, String outFilePath, int bufferSize)
{
this.event = event;
this.url = url;
this.outFilePath = outFilePath;
this.bufferSize = bufferSize;
}
@Override
public void run()
{
try
{
download();
}
catch (IOException e)
{
throw new RuntimeException(e);
}
}
public void download() throws IOException
{
// 下載下傳的檔案儲存在本地的路徑
File outFile = new File(outFilePath);
long finishedSize = 0;
if (outFile.exists())
// 如果檔案已經存在，記錄檔案大小，即已下載下傳大小
finishedSize = outFile.length();
URL download_url = new URL(url);
Socket socket = new Socket();
// 擷取主機位址
String host = download_url.getHost();
// 擷取端口 如果url位址沒有指定端口 會傳回-1 給定一個預設端口号80
int port = download_url.getPort() == -1 ? 80 : download_url.getPort();
// 資料路徑
String resourcePath = download_url.getPath();
event.state("connecting " + host + ":" + port);
// 設定read逾時
socket.setSoTimeout(5000);
// 連接配接伺服器 并且設定連接配接逾時
socket.connect(new InetSocketAddress(host, port), 3000);
event.state("connect successfully");
try
{
// 生成一個request消息，用于檢視所下載下傳檔案大小和伺服器是否支援斷點下載下傳
generateHttpRequest(socket, host, resourcePath, finishedSize);
InputStream socketIn = socket.getInputStream();
// 解析響應頭資訊
analyseResponseHeader(socketIn, event);
// 擷取要下載下傳檔案的大小
long contentLength = getFileLength();
// 如果已下載下傳的大小大于等于總的檔案大小 直接傳回
if (contentLength <= finishedSize)
return;
// 如果已下載下傳大小不等于0 且狀态碼是200（表示伺服器不支援斷點下載下傳
// Accept-Ranges: bytes也可以用來判斷伺服器是否支援斷點下載下傳） 也直接傳回
if (finishedSize > 0 && "200".equals(responseCode))
return;
//206表示支援斷點下載下傳 其他狀态碼就抛出一個運作時異常
if (responseCode.charAt(0) != '2')
throw new RuntimeException("Unsupported response status code");
byte[] buf = new byte[bufferSize];
int n;
FileOutputStream fos = new FileOutputStream(outFile, true);
try
{
while (-1 != (n = socketIn.read(buf)))
{
fos.write(buf, 0, n);
finishedSize += n;
//計算目前已下載下傳百分比
event.percent(finishedSize * 100 / contentLength);
}
}
finally
{
if (fos != null)
{
try
{
fos.close();
}
catch (Exception e)
{
}
}
}
}
finally
{
socket.close();
}
}
private String getHeader(String name)
{
return headers.get(name);
}
private int getIntHeader(String name)
{
return Integer.parseInt(getHeader(name).trim());
}
private long getFileLength()
{
long len = -1;
try
{
len = getIntHeader("Content-Length");
String[] parts = getHeader("Content-Range").split("/");
if (parts.length > 1)
len = Integer.parseInt(parts[1].trim());
else
len = -1;
}
catch (Exception e)
{
}
return len;
}
private void analyseResponseHeader(InputStream socketIn, DownloadEvent event) throws IOException
{
String line = "";
while (true)
{
int bt = socketIn.read();
if (bt == '\r')
{
bt = socketIn.read();
if (bt == '\n')
{
//如果讀到空行，就結束解析
if ("".equals(line))
break;
//解析狀态行和頭資訊
addHeader2Map(line);
event.viewHeader(line);
line = "";
}
}
else
line += (char) bt;
}
}
private void addHeader2Map(String line)
{
int index = line.indexOf(":");
if (index > 0)
headers.put(line.substring(0, index).trim(), line.substring(index + 1));
else
analyseResponseLine(line);
}
private void analyseResponseLine(String line)
{
String[] parts = line.split(" +");
if (parts.length > 1)
//擷取狀态碼
responseCode = parts[1].trim();
}
private void generateHttpRequest(Socket socket, String host, String path, long startPos) throws IOException
{
PrintWriter writer = new PrintWriter(socket.getOutputStream());
writer.println("GET " + path + " HTTP/1.1");
writer.println("Host: " + host);
writer.println("User-Agent: java");
if (startPos > 0)
//如果已下載下傳長度不為0 就通過Range頭把已下載下傳長度也一起發送給伺服器
writer.println("Range: bytes=" + startPos + "-");
writer.println("Connection: close");
writer.println();
writer.flush();
}
public interface DownloadEvent
{
void state(String message);
void viewHeader(String header);
void percent(long newValue);
}
}
class DownloadProgress implements DownloadEvent
{
long oldValue = -1;
@Override
public void percent(long newValue)
{
if (newValue > oldValue)
{
System.out.print("[" + newValue + "%]");
oldValue = newValue;
}
}
@Override
public void state(String message)
{
System.out.println(message);
}
@Override
public void viewHeader(String header)
{
System.out.println(header);
}
}
/*
* 6688768 bytes 87494656 bytes 121552303 bytes
*/
public class Main
{
public static void main(String[] args) throws Exception
{
if (args.length < 1)
{
System.out.println("Usage: java class DownloadFileName");
return;
}
FileInputStream fis = new FileInputStream(args[0]);
BufferedReader fileReader = new BufferedReader(new InputStreamReader(fis));
String s = "";
String[] ss;
while ((s = fileReader.readLine()) != null)
{
ss = s.split("[ ]+");
if (ss.length > 2)
{
System.out.println("---------------------------");
System.out.println("downloading:" + ss[0]);
System.out.println("output file path:" + ss[1]);
System.out.println("buffer size:" + ss[2]);
System.out.println("---------------------------");
HttpDownloadSingle httpDownload = new HttpDownloadSingle(new DownloadProgress(), ss[0], ss[1], Integer
.parseInt(ss[2]));
new Thread(httpDownload).start();
}
}
fileReader.close();
}
}
運作結果
---------------------------
downloading:http://localhost:8080/test_web/xx.exe
output file path:src/xx.exe
buffer size:4096
---------------------------
connecting localhost:8080
connect successfully
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Accept-Ranges: bytes
ETag: W/"607195608-1397026780797"
Last-Modified: Wed, 09 Apr 2014 06:59:40 GMT
Content-Type: application/octet-stream
Content-Length: 607195608
Date: Wed, 16 Apr 2014 01:42:20 GMT
Connection: close
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