Transcript Ajax and XML

Ajax with XML
26-Jul-16
Displaying theAjax response
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Here is the previous code for dealing with a non-XML
response:
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function alertContents(http_request) {
if (http_request.readyState == 4) {
if (http_request.status == 200) {
alert(http_request.responseText);
} else {
alert('There was a problem with the request.');
}
}
}
Doing it with XML
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Here’s an XML file named test.xml:
<?xml version="1.0" ?>
<root> I'm a test. </root>
function alertContents(http_request) {
if (http_request.readyState == 4) {
if (http_request.status == 200) {
var xmldoc = http_request.responseXML;
var root_node =
xmldoc.getElementsByTagName('root').item(0);
alert(root_node.firstChild.data);
} else {
alert('There was a problem with the request.');
}
}
}
responseText and responseXML
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The Content-Type in the header tells the type of server
response
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For non-XML, you can use text/html or text/plain
For sending XML, it's better to use text/xml
When the server sends text/xml, the browser parses it,
creates an XML DOM tree, and places this tree in the
responseXML object
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The XML is also available in the responseText object, but it
you use this you will have to parse it yourself
HTML DOM vs. XML DOM
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The DOM for the web page represents HTML
The DOM for the XML represents the server's response
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They have the same methods!
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Sending XML to the server
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The server is really good at handling name-value pairs
If you want to send XML...
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It pretty much has to be sent as POST
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XML gets long very quickly
All those special characters need to be URL-encoded
You have to
setRequestHeader("Content-Type", "text/xml")
The server doesn't have DOM trees--you will have to parse
the XML yourself
Bottom line: Sending XML to the server is too much
work!
XML notes
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The XML response object supports very complete
XML DOM processing
The response header must include:
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Content-Type: text/xml
or IE will throw an “Object expected” JavaScript error
Cache-Control: no-cache
or the response will be cached and the request will never be
resubmitted
For some browsers you may need to do
request.overrideMimeType('text/xml');
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In Firefox, this will give an error if the response isn’t valid
XML
The End