Is DocumentBuilder.parse(..) reading the whole XML into memory?

Question

Hello,
I have a quick question about the following code snippet:
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse("books.xml");Please have a look at the last line "builder.parse("books.xml");". I would like to use XPath to retrieve some informations of a xml file without having to deserialize the whole file (since the XML file rather big and I need to go through several of them in a loop).
What exactly does the "builder.parse(...)" method? Is it reading the XML file and writing all the content to memory? Or does it only analyze and read the structure of the XML code? Or in other words, is the text of an element "//books/title" in memory after parsing, or not until I really access the "title" node of that XML?
Thanks a lot for your help
Best Regards,
Ben

Answer 1

Hi ,
I did'nt knew how to start a new thread , so i am asking the question here:
===========================================================
I am trying to read a xml file but i am not able to do so properly. I am new to xml .
am trying to read a xml file of the following format in the staf and stax job xml file:
<?xml version="1.0" encoding="utf-8"?>
<operating_system>
<unix_80sp1>
<tests type="quick_sanity_test">
<prerequisitescript>preparequicksanityscript</prerequisitescript>
<acbuildpath>acbuildpath</acbuildpath>
<testsuitscript>test quick sanity script</testsuitscript>
<testdir>quick sanity dir</testdir>
</tests>
<machine_name>u80sp1_L004</machine_name>
<machine_name>u80sp1_L005</machine_name>
<machine_name>xyz.pxy.dxe.cde</machine_name>
<vmware id="155.35.3.55">144.35.3.90</vmware>
<vmware id="155.35.3.56">144.35.3.91</vmware>
</unix_80sp1>
</operating_system>
Here machine_name tag can be n number. I need to read all the machine_name tags in an array , so that i can use them later.
Also i need to read all the vmware tags in an array (both value and attributes) so that i can use them later. The number of vmware tags can again be n numbers.
I am trying to use the following code :
<!-- ******************************************************************* -->
<!-- Following function is used to parse an XML file and return the DOM -->
<!-- document object -->
<!-- ******************************************************************* -->
<function name="parseXML" scope="local">
<function-list-args>
<function-required-arg name="xmlFileName">
Name of file containing XML to be parsed
</function-required-arg>
</function-list-args>
<sequence>
<!-- Parse the XML -->
<script>
factory = DocumentBuilderFactory.newInstance();
factory.setValidating(1)
factory.setIgnoringElementContentWhitespace(0)
builder = factory.newDocumentBuilder()
document = builder.parse(xmlFileName)
</script>
<script>
vmware = None
machine_name = None
# Get the text value for the element with tag name "vmware"
nodeList = document.getElementsByTagName("vmware")
for i in range(nodeList.getLength()):
node = nodeList.item(i)
if node.getNodeType() == Node.ELEMENT_NODE:
children = node.getChildNodes()
for j in range(children.getLength()):
thisChild = children.item(j)
if (thisChild.getNodeType() == Node.TEXT_NODE):
machine_name = thisChild.getNodeValue()
# Get the text value for the element with tag name "machine_name"
nodeList = document.getElementsByTagName("vmware")
for i in range(nodeList.getLength()):
node = nodeList.item(i)
if node.getNodeType() == Node.ELEMENT_NODE:
children = node.getChildNodes()
for j in range(children.getLength()):
thisChild = children.item(j)
if (thisChild.getNodeType() == Node.TEXT_NODE):
machine_name = thisChild.getNodeValue()
</script>
<return>[machine_name,vmware]</return>
</sequence>
</function>
I am able to read only one value for machine_name (u80sp1_L005) and also one value for vmware
i.e 144.35.3.91.
What i want is read all the machine_value tags into a list , so that i can use it later
Also i want to read all the vmware tags attributes into a list and all corresponding values into another list.
what i mean is considering the following:_
<machine_name>u80sp1_L004</machine_name>
<machine_name>u80sp1_L005</machine_name>
<machine_name>xyz.pxy.dxe.cde</machine_name>
<vmware id="155.35.3.55">144.35.3.90</vmware>
<vmware id="155.35.3.56">144.35.3.91</vmware>
read all machine_name tag values into one list (u80sp1_L004,u80sp1_L005,xyz.pxy.dxe.cde)
also all vmware attributes into one list *(155.35.3.55,155.35.3.56).....*and all the vmware values into one list *(144.35.3.90,144.35.3.91)*
Also a good link to understand parsing using doumentbilder factory would be good help.
Regards
Sangram
mail: [email protected]