无法读取服务器响应JavaException:javax.xml.xpath.XPathExpressionException:null

我正在尝试执行以下代码：

function post(url, options) {
if(options.query) {
    url += "?";
    var delimiter = "";
    for(var propName in (options.query||{})) {
        url += (delemiter + (propName + "=" + escape(options.query[propName])));
        delimiter = "&";
    }
}
document.write("Fetching " + url);
var code;

var body = options.body;
if(body == null) {
    throw {message:"Body is required"};
}

try {

    // Open Connection
    connection = new java.net.URL(url).openConnection();

    // Set timeout
    var timeout = options.timeout != null ? options.timeout : 10000;
    connection.setReadTimeout(timeout);
    connection.setConnectTimeout(timeout);

    // Method == POST
    connection.setRequestMethod("POST");

    // Set Content Type
    var contentType = "text/xml;charset=utf-8";
    connection.setRequestProperty("Content-Type", contentType);
    connection.setRequestProperty("SOAPAction", "login");
    connection.setRequestProperty("User-Agent", "webastra");

    // Set Content Length
    connection.setRequestProperty("Content-Length", body.length);

    // Silly Java Stuff
    connection.setUseCaches (false);
    connection.setDoInput(true);
    connection.setDoOutput(true); 

    //Send Post Data
    bodyWriter = new java.io.DataOutputStream(connection.getOutputStream());
    bodyWriter.writeBytes(body);
    bodyWriter.flush ();
    bodyWriter.close (); 

    code = connection.getResponseCode();

}
catch(e) {
    throw {message:("Socket Exception or Server Timeout: " + e), code:0};
}
if(code < 200 || code > 299) {
    throw {message:("Received non-2XX response: " + code), code:code};
}
 var is = null;
try {

    importPackage(java.io, java.net, javax.xml.xpath, org.xml.sax);
    is = connection.getInputStream();
    var str = new String(org.apache.commons.io.IOUtils.toString(is));

    var paths = "//serverUrl";
    var ips = new InputSource(is);
    var xPath = XPathFactory.newInstance().newXPath();
    ret = xPath.evaluate(paths, ips);

    document.write(" succ:" + ret);
    return str;
}
catch(e) {
    document.write("Failed to read server response" + e);
}
finally {
    try {if(is != null)is.close();} catch (err){}
}

}

 post("https://abc.com/services/Soap/c/28.0", {body : "<?xml     version=\"1.0\" encoding=\"utf-8\"?> <soap:Envelope    xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\"  xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"   xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"   xmlns:tns=\"urn:enterprise.soap.sforce.com\"> <soap:Header> <tns:LoginScopeHeader>   <tns:organizationId/> </tns:LoginScopeHeader> </soap:Header> <soap:Body> <tns:login>   <tns:username>abc@3clogic.com</tns:username>   <tns:password>Thursday12gtz</tns:password> </tns:login> </soap:Body>   </soap:Envelope>"});

函数帖子（url、选项）{
if（options.query）{
url+=“？”；
var分隔符=”；
for（在（options.query | |{}）中使用var propName）{
url+=（delemiter+（propName+“=”+escape（options.query[propName]））；
分隔符=“&”；
}
}
document.write（“抓取”+url）；
var代码；
var body=options.body；
if（body==null）{
抛出{message:“Body是必需的”}；
}
试一试{
//开放连接
connection=newjava.net.URL（URL.openConnection（）；
//设置超时
var timeout=options.timeout！=null？options.timeout:10000；
connection.setReadTimeout（超时）；
connection.setConnectTimeout（超时）；
//方法==POST
connection.setRequestMethod（“POST”）；
//设置内容类型
var contentType=“text/xml；charset=utf-8”；
setRequestProperty（“内容类型”，contentType）；
setRequestProperty（“SOAPAction”、“login”）；
setRequestProperty（“用户代理”、“webastra”）；
//设置内容长度
connection.setRequestProperty（“内容长度”，body.Length）；
//愚蠢的Java东西
connection.setUseCaches（false）；
connection.setDoInput（true）；
connection.setDoOutput（真）；
//发送Post数据
bodyWriter=new java.io.DataOutputStream（connection.getOutputStream（））；
bodyWriter.writeBytes（body）；
bodyWriter.flush（）；
bodyWriter.close（）；
代码=连接。getResponseCode（）；
}
捕获（e）{
抛出{消息：（“套接字异常或服务器超时：”+e），代码：0}；
}
如果（代码<200 | |代码>299）{
抛出{message:（“收到的非2XX响应：“+code”），code:code}；
}
var=null；
试一试{
importPackage（java.io、java.net、javax.xml.xpath、org.xml.sax）；
is=connection.getInputStream（）；
var str=新字符串（org.apache.commons.io.IOUtils.toString（is））；
var path=“//服务器URL”；
var ips=新输入源（is）；
var xPath=XPathFactory.newInstance（）.newXPath（）；
ret=xPath.evaluate（路径，IP）；
文件。写入（“成功：”+ret）；
返回str；
}
捕获（e）{
document.write（“读取服务器响应失败”+e）；
}
最后{
尝试{if（is！=null）is.close（）；}catch（err）{
}
}
职位（”https://abc.com/services/Soap/c/28.0“，{正文：”abc@3clogic.com周四12GTZ“}）；

post部分是成功的。但是，当我试图在变量ret中检索xml标记“serverUrl”的值时，出现以下错误：

无法读取服务器响应JavaException:javax.xml.xpath.XPathExpressionException:null

我从post检索到的xml是：

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
              xmlns="urn:enterprise.soap.sforce.com"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
    <loginResponse>
        <result>
            <metadataServerUrl>
               https://na3.salesforce.com/services/Soap/m/28.0/00D50000000IdrE
            </metadataServerUrl>
            <passwordExpired>false</passwordExpired>
            <sandbox>false</sandbox>
            <serverUrl>
                https://na3.salesforce.com/services/Soap/c/28.0/00D50000000IdrE
            </serverUrl>
            <sessionId>
                    00D50000000IdrE!AREAQK4VYXRaHoL_uRvOi.QXXw3ahAt2Cge254wygiW7cr_f6DVa2pDC6g57w5IE
                fidAu3ZRsJFBN5Bwb6DVhF18zKFiVVyT
            </sessionId>
            <userId>00550000001Dd4uAAC</userId>
            <userInfo>
                <accessibilityMode>false</accessibilityMode>
                <currencySymbol>$</currencySymbol>
                <orgAttachmentFileSizeLimit>5242880
                </orgAttachmentFileSizeLimit>
                <orgDefaultCurrencyIsoCode>USD</orgDefaultCurrencyIsoCode>
                <orgDisallowHtmlAttachments>false
                </orgDisallowHtmlAttachments>
                <orgHasPersonAccounts>false</orgHasPersonAccounts>
                <organizationId>00D50000000IdrEEAS</organizationId>
                <organizationMultiCurrency>false</organizationMultiCurrency>
                <organizationName>3CLogic</organizationName>
                <profileId>00e500000017al5AAA</profileId>
                <roleId xsi:nil="true"/>
                <sessionSecondsValid>7200</sessionSecondsValid>
                <userDefaultCurrencyIsoCode xsi:nil="true"/>
                <userEmail>ramana@3clogic.com</userEmail>
                <userFullName>Ramana</userFullName>
                <userId>00550Dd4uAAC</userId>
                <userLanguage>en_US</userLanguage>
                <userLocale>en_US</userLocale>
                <userName>raman@gmail.com.com</userName>
                <userTimeZone>America/New_York</userTimeZone>
                <userType>Standard</userType>
                <userUiSkin>Theme3</userUiSkin>
            </userInfo>
        </result>
    </loginResponse>
</soapenv:Body>
</soapenv:Envelope>

https://na3.salesforce.com/services/Soap/m/28.0/00D50000000IdrE
假的
假的
https://na3.salesforce.com/services/Soap/c/28.0/00D50000000IdrE
00D50000000印尼盾！区域QK4Vyxrahol_uRvOi.QXXW3AHAT2CE254WYGIW7CR_f6DVa2pDC6g57w5IE
fidAu3ZRsJFBN5Bwb6DVhF18zKFiVVyT
00550000001Dd4uAAC
假的
$
5242880
美元
假的
假的
00D50000000IdrEEAS
假的
3CLogic
00E5000017AL5AAA
7200
ramana@3clogic.com
拉马纳
00550Dd4uAAC
恩努斯
恩努斯
raman@gmail.com.com
美国/纽约
标准
主题3

当您尝试解析时，

输入流

已为“空”（即读取）：

is=connection.getInputStream（）；
var str=新字符串（org.apache.commons.io.IOUtils.toString（is））；//
var
来自哪里？那不是Java，对吗？