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我有一個Java程序通過HTTPS connection.The程序如下下載文件時，的Java：下載重啓
public class Download extends Observable implements Runnable {
private static final int MAX_BUFFER_SIZE = 1024;
public static final int DOWNLOADING = 0;
public static final int PAUSED = 1;
public static final int COMPLETE = 2;
public static final int CANCELLED = 3;
public static final int ERROR = 4;
private URL url; // download URL
private static float size; // size of download in bytes
private int downloaded; // number of bytes downloaded
private int status; // current status of download
private String location;
public Download(URL url,String location){
this.url = url;
size=-1;
downloaded=0;
status=DOWNLOADING;
this.location=location;
download();
}
public String getURL(){
return url.toString();
}
public static float getSize(){
return size;
}
public float getProgress(){
return ((float) downloaded/size) * 100;
}
public void pause(){
status = PAUSED;
stateChanged();
}
public void resume(){
status = DOWNLOADING;
stateChanged();
download();
}
public void cancel(){
status = CANCELLED;
stateChanged();
}
public void error(){
status = ERROR;
stateChanged();
}
private String getFileName(URL url){
String filepath = url.getFile();
int slashIndex = filepath.lastIndexOf("/");
String fileName = filepath.substring(slashIndex+1,filepath.length());
String downloadPath = location+"/"+fileName;
return downloadPath;
}
private void download(){
Thread thread = new Thread(this);
thread.start();
}
@Override
public void run() {
RandomAccessFile randomAccessFile = null;
InputStream inputStream = null;
int responseCode = 0;
try{
HttpsURLConnection connection = getSSLCertificate(getURL());
connection.setRequestMethod("GET");
connection.setRequestProperty("Range","bytes=" + downloaded + "-");
connection.connect();
responseCode=connection.getResponseCode();
if(responseCode/100 != 2){
error();
}
int contentLength = connection.getContentLength();
if(contentLength <1){
error();
}
if(size == -1){
size = contentLength;
stateChanged();
}
randomAccessFile = new RandomAccessFile(getFileName(url),"rw");
randomAccessFile.seek(downloaded);
inputStream = connection.getInputStream();
while(status == DOWNLOADING){
//byte buffer[]=new byte[3000000];
byte buffer[];
float finalSize=size - downloaded;
if (finalSize > MAX_BUFFER_SIZE) {
buffer = new byte[(int) finalSize];
} else {
buffer = new byte[MAX_BUFFER_SIZE];
}
int read = inputStream.read(buffer);
if(read == -1)
break;
randomAccessFile.write(buffer, 0, read);
downloaded += read;
stateChanged();
}
}catch (Exception e) {
e.printStackTrace();
}finally{
try {
randomAccessFile.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void stateChanged(){
setChanged();
notifyObservers();
}
private HttpsURLConnection getSSLCertificate(String urlPath) throws NoSuchAlgorithmException, KeyManagementException, IOException{
SSLContext ctx = SSLContext.getInstance("TLS");
ctx.init(new KeyManager[0],new TrustManager[]{new DefaultTrustManager()},new SecureRandom());
SSLContext.setDefault(ctx);
URL url = new URL(urlPath);
HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
conn.setHostnameVerifier(new HostnameVerifier() {
@Override
public boolean verify(String arg0, SSLSession arg1) {
return true;
}
});
return conn;
}
public static void main(String[] args) throws MalformedURLException {
System.out.println("Enter the URL and Press ENTER:");
Scanner scanner = new Scanner(System.in);
String link = scanner.nextLine();
System.out.println("Enter the destination location and Press ENTER:");
String destination=scanner.nextLine();
if(link.length() >0 && destination.length()>0){
Download d = new Download(new URL(link),destination);
System.out.println("Downloading... ");
d.run();
System.out.println("Downloaded Successfully" +" " +"Size:"+(getSize()/1048576) + " MB");
}else{
System.out.println("Error! Please provide url and destination location");
System.exit(1);
}
}
我需要實現一個恢復下載，即如果出現網絡癱瘓，而下載並再次上網，下載需要從停止點開始。