XML and JAXP
PB138
Intuitive introduction into XML
● XML is text
● Very often XML document is text file or string
● First line is called Prolog
<?xml version=”1.0” encoding=”UTF-8” ?>
<text>This is an XML document</text>
Element
start tag: <person>
end tag: </person>
● May contain text and/or other elements
Create Simple Well Formed XML
● Create an XML document (in a text file) that
contains 3 people. Each person has a name
and surname.
● Try xmllint to validate that your document is
well formed
XML Terminology
● well formed
○ It contains prolog (heading) and exactly one root
element. Before and after the root element, there
can be processing instructions, comments (Misc).
○ It meets all the well-formedness constraints given in
the specification.
● Parent vs Ancestor, Child vs Descendant
XML 1.0
● www.w3.org/TR/2008/REC-xml-20081126/
● http://www.xml.com/axml/axml.html
This is not well-formed prolog:
<?xml encoding='UTF-8' version='1.0'?>
Xml Attributes
● Attributes add information to elements
● One element cannot have 2 attributes with
same name (provided the namespaces of
the attributes are the same)
...
<person age="27">
...
XML Entities
● Variables/shortcuts
&lt; when you need to write <
&gt; for >
&amp; for &
● <![CDATA[SOME escaped TEXT]]>
Modify your document
● Add attribute age to your people
● Add “html name” element and using entities
put this into its content:
● <b>Filip</b>
Java API for XML parsing/writing
● Acronym JAXP
● http://docs.oracle.com/javase/8/docs/api/
○ org.w3c - important objects such as Document
○ javax.xml.parsers - for parsing Document from file
JAXP Documentation
● Find the methods for disabling validation and
namespace awarness in javadoc for
DocumentBuilderFactory
● Turn the features off in JaxpParser.java
Print Root Element Name
● Modify XmlIntroduction main class
● Use JaxpParser.getDocument to get
Document
● use Document to get the Document Element
(root Element) and print name the element
(tag name). The output should be “people”
Print names of people in people.xml
● use Document.getElementsByTagName to
get people elements
● Iterate through NodeList
○ int NodeList.getLength()
○ Node NodeList.item(int i)
● Cast each Node to Element and use
getAttribute to print out name of the person!
XML modifications
● in XmlIntroduction uncomment usage of
saveToFile method
● try to run the XmlIntroduction and inspect
people-new.xml
Method to get Elements
● Create method in XmlIntroduction that will
return List<Element> of elements of a
specific name
○ List<Element> getElements(Document doc,String
name);
○ use getElementsByTagName
Method to rename people
● Create method in XmlIntroduction that will
rename a person with some id: rename
(Document doc, int id, String newName);
○ Integer.parseInt
○ Element.setAttribute
Remove element
● Create method that will delete a person with
some id: delete(Document doc, int id);
○ x.getParentNode().removeChild(x)
Add element
● Create method that will add a new person
with some id: create(Document doc, int id,
String name);
○ Make sure the IDs in the document are unique!
○ use Document.createElement
○ use Element.appendChild