java访问WebService返回xml数据生成为本地文件

部分代码如下：
public class DomXMLString {

private static String SERVICES_HOST = "www.webxml.com.cn";

private static String NETDATA_URL = "http://183.131.242.70:8089/ship/interface/shipInfoService.asmx/getTask";

private static String LOCAL_PC_SAVEFILE_URL = "E:Myeclipse/sy_Task.xml";

private DomXMLString(){}

public static void main(String[] args)throws Exception {
    Document document = getTask(NETDATA_URL);
    helloOK(document,LOCAL_PC_SAVEFILE_URL);

}


private static Document getTask(String netXMLDataURL) {
    Document document = null;
    DocumentBuilderFactory documentBF = DocumentBuilderFactory.newInstance();
    documentBF.setNamespaceAware(true);
    try{
        DocumentBuilder documentB = documentBF.newDocumentBuilder();
        InputStream inputStream = getSoapInputStream(netXMLDataURL);
        document = documentB.parse(inputStream);
        inputStream.close();
    }catch(DOMException e){
        e.printStackTrace();
        return null;
    }catch(ParserConfigurationException e){
        e.printStackTrace();
        return null;
    }catch(SAXException e){
        e.printStackTrace();
        return null;
    }catch(IOException e){
        e.printStackTrace();
        return null;
    }
    return document;
}
运行提示错误为：
java.io.IOException: Server returned HTTP response code: 500 for URL: http://183.131.242.70:8089/ship/interface/shipInfoService.asmx/getTask
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1626)
at org.tempuri.DomXMLString.getSoapInputStream(DomXMLString.java:79)
at org.tempuri.DomXMLString.getTask(DomXMLString.java:52)
at org.tempuri.DomXMLString.main(DomXMLString.java:39)

Exception in thread "main" java.lang.IllegalArgumentException: InputStream cannot be null
at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:117)
at org.tempuri.DomXMLString.getTask(DomXMLString.java:53)
at org.tempuri.DomXMLString.main(DomXMLString.java:39)
之前也查了一些资料，想请问是不是我设置的路径有问题以及解决办法，求大神指点迷津