Java implementation http File download __java

Using proxy servers in Java ask for advice: http://www.linuxsir.org/bbs/archive/index.php/t-188774.html preface

Many users may experience a situation like this: found a good resource on the site, but this resource is divided into a lot of files stored, if you want to save it to the local, only rely on the user click on save to complete, if the resources divided hundreds of or even thousands of thousands, it is a disaster.

When a lot of resources on the Internet are stored in multiple files, it has a certain rule of naming the file, and because of this, we can use the program to complete the full download of this resource.

　　 1. Basic Knowledge

On the Internet, we want to download a resource on the site, we will get a URL (uniform Resource Locator), it is a description of the server resource positioning, the process of downloading is always the following steps:

Step 1: The client initiates a connection request a URL

Step 2: The server resolves the URL and returns the specified resource to an input stream to the customer

Step 3: The client receives the input stream and saves the contents of the stream to the file

　　 2. The establishment of network connection

Java provides a URL access and a large number of streaming operations of the API, we can easily complete access to resources on the network, the following code snippet completes the resources of a Web site to access:

...... Desturl= "http://www.ebook.com/java/network programming 001.zip"; url = new URL (desturl); Httpurl = (httpurlconnection) url.openconnection (); Connecting to a specified network resource Httpurl.connect (); Get network input stream bis = new Bufferedinputstream (Httpurl.getinputstream ()); ......

　　 3. Access by proxy

The way to access the extranet through proxy servers in Java is already known as the Secret of the world. Here is no longer described, access to the Java code is as follows:

Setting up a proxy server System.getproperties (). Put ("Proxyset", "true"); System.getproperties (). Put ("ProxyHost", "10.154.134.110"); System.getproperties (). Put ("ProxyPort", "8080");

　　 4. The preservation of network resources

In the previous section, we've got the input stream for the specified network resource, so what we're going to do is read the contents of the input stream and save it in the file. Sample code:

...... FOS = new FileOutputStream (fileName); if (this. DEBUG) System.out.println ("Getting the content of the link [" + Desturl +] ...)./n Save it as a file [+ FileName +]]; Save File while (size = Bis.read (BUF))!=-1) Fos.write (buf, 0, size); ......

The example code above saves the contents of a network resource to a locally specified file.

　　5. Code Listings

Import java.io.*;
Import java.net.*;
Import java.util.*;

/**
*

Description: Store the specified HTTP network resources locally as files

**/
public class SaveFile {

Public final Static Boolean DEBUG = true; Adjust the trial
private static int buffer_size = 8096; Buffer size
Private vector vdownload = new vector (); URL List
Private vector vfilelist = new vector (); List of saved file names after download

/**
* Construction Method
*/
Public SaveFile () {}

/**
* Clear Download List
*/
public void Resetlist () {
Vdownload.clear ();
Vfilelist.clear ();
}

/**
* Add Download list items
*
* @param URL String
* @param filename String
*/

public void AddItem (string url, string filename) {
Vdownload.add (URL);
Vfilelist.add (filename);
}

/**
* Download resources from the list
*/
public void Downloadbylist () {
String URL = null;
String filename = null;

Save Resources in List order
for (int i = 0; i < vdownload.size (); i++) {
url = (String) vdownload.get (i);
filename = (String) vfilelist.get (i);

            try {
                 savetofile (URL, filename);
           } catch (IOException err) {
                 if (DEBUG) {
                     SYSTEM.OUT.PRINTLN ("resource [" + URL + "] Download failed!!!");
               }
           }
       }

        if (DEBUG) {
             System.out.println ("Download complete!!!");
       }
   }

   /**
     * Save HTTP resource as file
     *
      * @param desturl string
     * @param fileName string
     * @throws Exception
     */
    public void SaveToFile (string desturl, String FileName) throws IOException {
        fileoutputstream fos = null;
        Bufferedinputstream bis = null;
        httpurlconnection httpurl = null;
        URL url = null;
        byte[] buf = new Byte[buffer_size];
        int size = 0;
       

//Create link
        url = new URL (desturl);
        Httpurl = (httpurlconnection) url.openconnection ();
//connection specified resources
        httpurl.connect ();
Get the network input stream
        bis = new Bufferedinputstream (Httpurl.getinputstream ());
Create file
        fos = new FileOutputStream (fileName);

if (this. DEBUG)
System.out.println ("Getting the content of the link [+ Desturl +]"] .../n save it as a file [+
FileName + "]");
Save File
while (size = Bis.read (BUF))!=-1)
Fos.write (buf, 0, size);

Fos.close ();
Bis.close ();
Httpurl.disconnect ();
}

/**
* Save HTTP resource as File
*
* @param desturl String
* @param fileName String
* @throws Exception
*/
public void SaveToFile2 (string desturl, String fileName) throws IOException {
FileOutputStream fos = null;
Bufferedinputstream bis = null;
HttpURLConnection httpurl = null;
URL url = null;
byte[] buf = new Byte[buffer_size];
int size = 0;

Create a link
url = new URL (desturl);
Httpurl = (httpurlconnection) url.openconnection ();

String authstring = "username" + ":" + "password";
String authstring = "50301" + ":" + "88888888";
String auth = "Basic" +
New Sun.misc.BASE64Encoder (). Encode (Authstring.getbytes ());
Httpurl.setrequestproperty ("Proxy-authorization", auth);

Connect the specified resource
Httpurl.connect ();
Get network input stream
bis = new Bufferedinputstream (Httpurl.getinputstream ());
Create a file
FOS = new FileOutputStream (fileName);

if (this. DEBUG)
System.out.println ("Getting the content of the link [+ Desturl +]"] .../n save it as a file [+
FileName + "]");
Save File
while (size = Bis.read (BUF))!=-1)
Fos.write (buf, 0, size);

Fos.close ();
Bis.close ();
Httpurl.disconnect ();
}

/**
* Set Proxy Server
*
* @param proxy String
* @param proxyport String
*/
public void Setproxyserver (string proxy, string proxyport) {
Setting up a proxy server
System.getproperties (). Put ("Proxyset", "true");
System.getproperties (). Put ("ProxyHost", proxy);
System.getproperties (). Put ("ProxyPort", ProxyPort);
}

public void Setauthenticator (string uid, string pwd) {
Authenticator.setdefault (New Myauthenticator ());
}

/**
* Main method (for testing)
*
* @param argv string[]
*/
public static void Main (String argv[]) {
HttpGet oinstance = new HttpGet ();
try {
Add Download list (where users can write their own code to increase the download list)
Oinstance.additem ("http://www.ebook.com/java/Network Programming 001.zip", "./network Programming 1.zip");/
Oinstance.additem ("http://www.ebook.com/java/Network Programming 002.zip", "./network Programming 2.zip");
Oinstance.additem ("http://www.ebook.com/java/Network Programming 003.zip", "./network Programming 3.zip");
Start download
Oinstance.downloadbylist ();
Oinstance.savetofile ("http://www.ebook.com/java/Network Programming 001.zip", "./down.zip");
}
catch (Exception err) {
System.out.println (Err.getmessage ());
}
}
}