java未知主机异常无法解决

Question

I Wanted to download one zip file from one URL, for that I Used the below code to open an URL and download one zip file from .But what happens is I am getting following exception

java.net.UnknownHostException: www.abc.com

So I just did some reasearch and guessed that could be the problem of certficate and generated the certificate by using below keytool command

keytool -genkey -keyalg RSA -alias selfsigned -keystore keystore.jks -storepass password -validity 360 -keysize 2048

After that I set the location of generated keystore.jks file by using the following code

 System.setProperty("javax.net.ssl.trustStore","C:\\Programme\\Java\\jdk1.6.0_31\\jre\\bin\\keystore.jks");

After running the code, still I am getting the same exception

java.net.UnknownHostException: www.abc.com 

Any idea how to ressolve? I am able to access this site from the Browser.

My full code below:

import java.io.*;
import java.net.*;

public class UrlDownload {
    final static int size = 1024;

    public static void fileUrl(String fAddress, String localFileName,
            String destinationDir) {
        OutputStream outStream = null;
        URLConnection uCon = null;

        InputStream is = null;
        try {
            URL Url;
            byte[] buf;
            int ByteRead, ByteWritten = 0;
            Url = new URL(fAddress);
            outStream = new BufferedOutputStream(new FileOutputStream(
                    destinationDir + "\\" + localFileName));

            uCon = Url.openConnection();
            is = uCon.getInputStream();
            buf = new byte[size];
            while ((ByteRead = is.read(buf)) != -1) {
                outStream.write(buf, 0, ByteRead);
                ByteWritten += ByteRead;
            }
            System.out.println("Downloaded Successfully.");
            System.out.println("File name:\"" + localFileName
                    + "\"\nNo ofbytes :" + ByteWritten);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
                outStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void fileDownload(String fAddress, String destinationDir) {
        int slashIndex = fAddress.lastIndexOf('/');
        int periodIndex = fAddress.lastIndexOf('.');

        String fileName = fAddress.substring(slashIndex + 1);

        if (periodIndex >= 1 && slashIndex >= 0
                && slashIndex < fAddress.length() - 1) {
            fileUrl(fAddress, fileName, destinationDir);
        } else {
            System.err.println("path or file name.");
        }
    }

    public static void main(String[] args) {

        String url = "http://www.abc.com/coolsolutions/tools/downloads/ntradping.zip";
        System.setProperty("javax.net.ssl.trustStore","C:\\Programme\\Java\\jdk1.6.0_31\\jre\\bin\\keystore.jks");
            String destAddress = "C:\\downloads";
                fileDownload(url,destAddress);

        } 
    }

I tried the below code. That throws unknown host exception.

InetAddress inetAddress = InetAddress.getByName("http://www.google.com");
    String ipAddress = inetAddress.getHostAddress().toString()'
    System.out.println(ipAddress );

Answer 1

Cause of this Exception according to javadocs is, Thrown to indicate that the IP address of a host could not be determined. So check the fAddress String.

try passing " http://www.novell.com/home/ " in your fAddress variable insteat "www.novell.com"

Hope it helps..