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我想从一个 URL 下载一个 zip 文件，为此我使用下面的代码打开一个 URL 并从中下载一个 zip 文件。但是会发生什么是我得到以下异常

java.net.UnknownHostException: www.abc.com

所以我只是做了一些研究并猜测这可能是证书的问题，并使用下面的 keytool 命令生成了证书

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

之后，我使用以下代码设置生成的 keystore.jks 文件的位置

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

运行代码后，我仍然得到相同的异常

java.net.UnknownHostException: www.abc.com

知道如何解决吗？我可以从浏览器访问该站点。

我的完整代码如下：

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);

        } 
    }

我尝试了下面的代码。这会引发未知主机异常。

InetAddress inetAddress = InetAddress.getByName("http://www.google.com");
    String ipAddress = inetAddress.getHostAddress().toString()'
    System.out.println(ipAddress );
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1 回答 1

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根据 javadocs，此异常的原因是，抛出表示无法确定主机的 IP 地址。所以检查 fAddress 字符串。

尝试在您的 fAddress 变量中传递“ http://www.novell.com/home/ ”而不是“www.novell.com”

希望能帮助到你..

于 2013-11-06T11:22:30.803 回答