Java's HTTP file queue download
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Author: Yang Liao
About the Author
Yang Liao, software engineer, you can get in touch with the author through magicsliao@yahoo.com.cn.
Preface
Many users may encounter such situations: I found a good resource on the website, but this resource is divided into many files. If you want to save it to your locally, you only click on the user to complete save, if The resources have been divided into several hundred or even thousands of thousands of people, which is a disaster.
When there are many resources on the Internet, it is a certain rule when it is stored in multiple files. For this reason, we can use the program to complete the full download of this resource.
Basic knowledge
On the Internet, we have to download a resource on the website, we will get a URL (Uniform Resource Locator), which is a description of a server resource location, the process of downloading is always as follows:
Step 1: Client initiates a connection request A URL Step 2: The server parses the URL and returns the specified resource to the client step 3: The client receives the input stream, save the content in the stream to the file
2. Establishment of network connection
Java provides an API for URL access and a large number of stream operations. We can easily complete access to resources on the network. The following code segments have completed access to a website for access:
......
Desturl = "http://www.ebook.com/java/ Network Programming 001.zip";
URL = New URL (DESTURL);
Httpurl = (httpurlconnection) URL.OpenConnection ();
/ / Connect the designated network resources
httpurl.connect ();
// Get network input streams
BIS = New BufferedInputStream (httpurl.getinputStream ());
......
3. Agent access
The method of accessing the external network through the proxy server in Java is already a secret of the world. There is no more described here, and the Java code accessed is as follows:
// Set proxy server
System.getProperties (). Put ("Proxyset", "True");
System.getProperties (). Put ("proxyhost", "10.154.134.110");
System.getProperties (). Put ("proxyport", "8080");
4. Saving of network resources
In the previous section, we have obtained the input stream of the specified network resource. Next, we must complete the content in the input stream, and save it in the file. Sample code:
......
FOS = New FileOutputStream (filename);
IF (this.debug)
System.out.Println ("" "is getting link [ DestURL "] ... / n is saved as file [" filename "] ");
//save document
While (size = bis.read (buf))! = -1)
Fos.Write (buf, 0, size);
......
The sample code above saves the content of the network resource to the local specified file.
5. Code list
Download source code HTTPGET.JAVA
Import java.io. *;
Import java.net. *;
Import java.util. *;
/ **
* Title: Personal development API
* Description: Store the specified HTTP network resource in the locality * Copyright: CopyRight (C) 2004
* Company: Newsky
* @Author Magicliao
* @version 1.0
* /
Public class httpget {
Public final static boolean debug = true; // debugging
Private static int buffer_size = 8096; // buffer size
Private vector vdownload = new vector (); // URL list
Private vector vfilelist = new vector (); // Download the saved file name list
/ **
* Construction method
* /
Public httpget () {
}
/ **
* Clear download list
* /
Public void resetlist () {
vdownload.clear ();
vfilelist.clear ();
}
/ **
* Add a download list item
*
* @Param URL String
* @Param FileName String
* /
Public void additem (string url, string filename) {
vDownload.add (URL);
vfilelist.add (filename);
}
/ **
* Download resources according to the list
* /
Public void downloadbylist () {
String Url = NULL;
String filename = NULL;
/ / Save resources in list order
For (int i = 0; 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 resources as file * * @Param Desturl String * @Param FileName String * @Throws Exception * / Public void savetofile (string desturl, string filename) throws oException { Fileoutputstream fos = NULL; BufferedInputStream Bis = NULL; HTTPURLCONNECTION httpurl = null; URL URL = NULL; BYTE [] BUF = New byte [buffer_size]; INT size = 0; // Establish a link URL = New URL (DESTURL); Httpurl = (httpurlconnection) URL.OpenConnection (); // Connect the specified resource httpurl.connect (); // Get network input streams BIS = New BufferedInputStream (httpurl.getinputStream ()); // Establish file fos = new fileoutputstream (filename); IF (this.debug) System.out.Println ("" "is getting link [ DestURL "] ... / n is saved as file [" filename "] "); //save document 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) { // Set proxy server System.getProperties (). Put ("Proxyset", "True"); System.getProperties (). PUT ("proxyhost", proxy; System.getProperties (). PUT ("proxyport", proxyport; } / ** * Set the authentication user name and password * * @Param Uid String * @Param PWD STRING * / Public void setauthenticator (String Uid, String PWD) { Authenticator.SetDefault (New MyAuthenTicator (UID, PWD)); } / ** * Main method (for testing) * * @Param Argv String [] * / Public static void main (String Argv []) { HTTPGET OINSTANCE = New httpget (); Try { / / Add a list of downloads (here 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 program 002.zip", "./ Network programming 2.zip"); Oinstance.additem ("http://www.ebook.com/java/ network program 003.zip", "./ Network programming 3.zip"); Oinstance.additem ("http://www.ebook.com/java/ network programming 004.zip", "./ Network programming 4.zip"); Oinstance.Additem ("http://www.ebook.com/java/ network program 005.zip", "./ Network programming 5.zip"); Oinstance.additem ("http://www.ebook.com/java/ network programming 006.zip", "./ Network program 6.zip"); Oinstance.addItem ("http://www.ebook.com/java/ network programming 007.zip", "./ Network programming 7.zip"); //start download Oinstance.downloadBylist (); } Catch (Exception Err) { System.out.println (Err.getMessage ()); } } ? Source code: import java.io. *; Import java.net. *; Import java.util. *; / ** * Title: Personal development API * Description: Store the specified HTTP network resources locally in file form * Copyright: Copyright (c) 2004 * Company: Newsky * @Author Magicliao * @version 1.0 * / Public class httpget { Public final static boolean debug = true; // debugging Private static int buffer_size = 8096; // buffer size Private vector vdownload = new vector (); // URL list Private vector vfilelist = new vector (); // Download the saved file name list / ** * Construction method * / Public httpget () { } / ** * Clear download list * / Public void resetlist () { vdownload.clear (); vfilelist.clear (); } / ** * Add a download list item * * @Param URL String * @Param FileName String * / Public void additem (string url, string filename) { vDownload.add (URL); vfilelist.add (filename); } / ** * Download resources according to the list * / Public void downloadbylist () { String Url = NULL; String filename = NULL; / / Save resources in list order For (int i = 0; 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 resources as file * * @Param Desturl String * @Param FileName String * @Throws Exception * / Public void savetofile (string desturl, string filename) throws oException { Fileoutputstream fos = NULL; BufferedInputStream Bis = NULL; HTTPURLCONNECTION httpurl = null; URL URL = NULL; BYTE [] BUF = New byte [buffer_size]; INT size = 0; // Establish a link URL = New URL (DESTURL); httpurl = (httpurlconnection) URL.OpenConnection (); // Connect the specified resource httpurl.connect (); // Get network input streams BIS = New BufferedInputStream (httpurl.getinputStream ()); // Establish a file FOS = New FileOutputStream (filename); IF (this.debug) System.out.Println ("" "is getting link [ DestURL "] ... / n is saved as file [" filename "] "); //save document 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) { // Set proxy server System.getProperties (). Put ("Proxyset", "True"); System.getProperties (). PUT ("proxyhost", proxy; System.getProperties (). PUT ("proxyport", proxyport; } / ** * Set the authentication user name and password * * @Param Uid String * @Param PWD STRING * / Public void setauthenticator (String Uid, String PWD) { Authenticator.SetDefault (New MyAuthenTicator (UID, PWD)); } / ** * Main method (for testing) * * @Param Argv String [] * / Public static void main (String Argv []) { HTTPGET OINSTANCE = New httpget (); Try { / / Add a list of downloads (here 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 program 002.zip", "./ Network programming 2.zip"); Oinstance.additem ("http://www.ebook.com/java/ network program 003.zip", "./ Network programming 3.zip"); Oinstance.additem ("http://www.ebook.com/java/ network programming 004.zip", "./ Network programming 4.zip"); Oinstance.Additem ("http://www.ebook.com/java/ network program 005.zip", "./ Network programming 5.zip"); Oinstance.additem ("http://www.ebook.com/java/ network programming 006.zip", "./ Network program 6.zip"); Oinstance.addItem ("http://www.ebook.com/java/ network programming 007.zip", "./ Network program 7.zip"); // Start download Oinstance.downloadBylist (); } Catch (Exception Err) { System.out.println (Err.getMessage ()); } } }
