How to use XPATH in XML

First ,  you need to use some tool (i.e. Dom4j) to read in an XML file (as your source file).

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String filename = "C:\\Test\\myTest.xml"; 

SAXReader reader = new SAXReader(); 

Document doc = null; 

try {    doc = reader.read(new File(filename));} 

catch (MalformedURLException e) {    e.printStackTrace();} catch (DocumentException e) {    e.printStackTrace();}

Second, You need to define the XPath expression. (Not necessary but recommended to write them in separate code)
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String findAllBread = "//bread";     

/* any element whose tag is "bread"  */

String findMyMilk = "//person[@name='me']/milk";     

/** any element whose name is "milk" and, is the direct child of element (tag "person"), and the parent element has attribute "name", and the value of "name" attribute is "me" */

Please refer to http://www.w3schools.com/xpath/ for detail of XPATH grammar


Third, you can use your xpath expression to get corresponding content now.
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List breads = doc.selectNodes(findAllBread);
Element myMilk = (Element) doc.selectSingleNode(findMyMilk);
for (Iterator iter = breads.iterator();iter.hasNext();){
Element ele = (Element)iter.next();
System.out.println("Bread  Weight="+ele.attributeValue("weight"));
}
System.out.println("My Milk is "+myMilk.attributeValue("weight"));

Result:

XML file (breakfirst.xml)
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<?xml version="1.0" encoding="UTF-8"?>
<menu>
<person name="me">
<message>You have new Email Today</message>
<bread weight="100g"></bread>
<milk weight="200g"></milk>
<egg number="1"></egg>
</person>
<person name="bill">
<message>You Have to go to school today</message>
<bread weight="200g"></bread>
<milk weight="500g"></milk>
<egg number="1"></egg>
</person>
</menu>

Result:
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Bread  Weight=100g
Bread  Weight=200g
My Milk is 200g

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