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I have a simple servlet application that sends XML response to JavaScript. When I check in my Firebug, This resposonse is received by JavaScript as 

<valid> AT&T,0.51851370625875,0.97944711419669,Verizon,0.47641942539114,0.99005717081381,wifi,0.48596657869633,0.88912486160201 </valid>

Which is a perfectly valid XML response - but Firebug also shows XML error 

XML Parsing Error: not well-formed Location: moz-nullprincipal:{30f70c51-7f01-48b4-9f69-4f0093e02ba6} Line Number 1, Column 12:
<valid>AT&T,0.51851370625875,0.97944711419669,Verizon,0.47641942539114,0.9900571...

It shows the error at the first comma - which does not makes sense at all. I even tried replacing commas with spaces - but even that gives same problem.

I generate my response from Servlet by 

String ret="";

for (int i=0; i < ping.size(); i++)
{

    ret += ping.get(i) ;
    if(i != ping.size()-1){
        ret += ",";
    }                   
}

response.setContentType("text/xml");           
response.setHeader("Cache-Control", "no-cache");

response.getWriter().write("<valid>"+ret+"</valid>");

And in my JavaScript, I try to retrieve data as 

var message = xmlHttp.responseXML.getElementsByTagName("valid")[0].childNodes[0].nodeValue;

I have use this exact same approach before - not sure why is this not working anymore. All I need to do is store the values (AT&T,0.51851370625875,0.97944711419669,Verizon,0.47641942539114,0.99005717081381,wifi,0.48596657869633,0.88912486160201) in a javascript array.

Any ideas?

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Please indent code with four spaces, as it says in the help section. – SLaks May 18 '11 at 1:59
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2 Answers

up vote 0 down vote

As said, this isn't valid XML. The & is a special character in XML.

You want to use Apache Commons Lang StringEscapeUtils#escapeXml() to escape special characters in XML. First download commons-lang-2.6.jar, drop it in /WEB-INF/lib folder and replace the last line of your servlet as follows:

response.getWriter().write("<valid>" + StringEscapeUtils.escapeXml(ret) + "</valid>");

Unrelated to the concrete problem, your String concatenation loop with += is pretty inefficient. Consider using StringBuilder instead.

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up vote 2 down vote

The issue is the & in AT&T. You have to escape out that character not the comma.

The reason you get the error at the first comma is that it's trying to parse &T as an html character.

The replace should be &#38; for an ampersand

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