3. JAXP wrap up
XML Namespaces
PB138
Homework
● Homework can be found here
/el/1433/jaro2013/PB138/ulohy/1/
● Deadline is 11.3.2013 23:59
● You can be awarded -3 points (fake)
● Late and corrected 0
● You can be awarded +3 for correct solution
● Use only JAXP, please study any method
you are going to use in JavaDoc
Get Tiger Woods Tweets
● Get tweets-woods-big.xml
● Find the text of the 10 most retweeted
tweets
Adding elements
● create method addSalary(personId, int
salary) which adds <salary>50000</salary>
● use Document.createElement
● use setTextContent
● use Element.appendChild
● create another method increaseSalary
(personId, amount) which will increase
salary
○ use Integer.parseInt
Modify Tiger Woods tweets
● Create new xml document with elements
<tweets>
<tweet retweetcount=”XYZ”>
Text of the tweet.
</tweet>
</tweets>
use saveToFile
● After saving you can see the DOCTYPE is
lost
● transformer.setOutputProperty( OutputKeys.
DOCTYPE_SYSTEM, document.
getDoctype().getSystemId());
Revising JAXP
● Create method in JAXP that will recursively
list all the nodes of social_network.xml
document
○ print getNodeName()
○ print human readable getNodeType()
■ use switch statement
XML Namespace
● element might be in namespace
<person xmlns="http://muj.namespace">....
● xmlns puts the element and all its
descendant elements into the namespace
● Create XML with 2 people. All the elements
in the document will be in namespace "my.
own.namespace".
XML Namespace
● We may use prefix to have fine control
● Prefix is usable in the same element or its
descendants
<person xmlns="http://muj.namespace" xmlns:meno="
http://muj.jmenny.namespace">
<meno:name>Filip</name>
</person>
● Add attribute firstname to elements and put
them into namespace "jmena"
● Add subelements surname into namespace
"prijmeni"
XML Namespaces
● put <social_network> and all its subelements
into namespace "social.seminar.fi.muni.cz"
● put Steven Segal person and all his
subelements into "people.type.hollywood"
namespace
● put all the <phones> and <phone> elements
into "contact.phones" namespace
XML Namespaces
● Find out in which namespace is attribute
phone/@number of Steven Segal.
○ Tip: .getAttributes().item(x).getNamespaceURI()
● Find out in which namespace is some
@xmlns attribute
XPath
● http://www.xpathtester.com/
○ put our social_network.xml there without
namespaces!
○ check output to new window
● XPath version 1.0, 2.0
● //person
● descendant-or-self:person
● /descendant-or-self:person
Basic XPath syntax
● Path to a set of elements: step/step/step/...
● basic step is "axisname::nodetest"
● Processing starts at invisible context node
"Document" step by step
● child::social_network/child::people/child::person
XPath evaluation sequence
● During evaluation, there is always one context node. At
the very beginning, the context node is invisible "root of
the document"
● '/' at the beginning will ensure, evaluation starts with
context node as a root of the document
● child::social_network/child::people/child::person
○ 1. from child axis of context node, select all
social_network elements
○ 2. for each result from 1.: set as context node, from
child axis select elements called "people"
○ 3. for each result from 2.: set as context node, from
child axis select elements called "person"
DOM4J
● http://dom4j.sourceforge.net/dom4j-1.6.1/apidocs/index.html
● Use Dom4JParser and implement
printDocumentElement()
○ getRootElement()
● Use Dom4JParser and implement
printPeopleNames()
○ getRootElement() to get the element
○ then use methods element() and elements()
Basic XPath usage
● The above says "from children, select social_network.
Take result and from each child of each result element
take person elements.....
● Shortcut:social_network/people/person
● Try getting all the phone elements using axis "child"
● Try getting <phone> elements using descendant axis
● Try getting people names using attribute axis
Homework
● Learn all axis
● Learn all nodetest
● Play with XPath
Next week
● XPath in depth