- Apache Xerces - Home
- Apache Xerces - XML Overview
- Apache Xerces - Environment Setup
- Apache Xerces - XML Parsers
Xerces DOM Parser
- Apache Xerces - DOM Parser
- Apache Xerces - Parse XML Document
- Apache Xerces - Query XML Document
- Apache Xerces - Create XML Document
- Apache Xerces - Modify XML Document
Xerces SAX Parser
- Apache Xerces - SAX Parser
- Apache Xerces - Parse XML Document
- Apache Xerces - Query XML Document
- Apache Xerces - Create XML Document
- Apache Xerces - Modify XML Document
Xerces StAX Parser
- Apache Xerces - StAX Parser
- Apache Xerces - Parse XML Document
- Apache Xerces - Query XML Document
- Apache Xerces - Create XML Document
- Apache Xerces - Modify XML Document
Xerces Useful Resources
Xerces - Quick Guide
Apache Xerces - XML Overview
What is XML?
XML is a simple text-based language which was designed to store and transport data in plain text format. It stands for Extensible Markup Language. Following are some of the salient features of XML.
XML is a markup language.
XML is a tag based language like HTML.
XML tags are not predefined like HTML.
You can define your own tags which is why it is called extensible language.
XML tags are designed to be self-descriptive.
XML is a W3C Recommendation for data storage and transport.
Example
<?xml version = "1.0"?>
<Class>
<Name>First</Name>
<Sections>
<Section>
<Name>A</Name>
<Students>
<Student>Rohan</Student>
<Student>Mohan</Student>
<Student>Sohan</Student>
<Student>Lalit</Student>
<Student>Vinay</Student>
</Students>
</Section>
<Section>
<Name>B</Name>
<Students>
<Student>Robert</Student>
<Student>Julie</Student>
<Student>Kalie</Student>
<Student>Michael</Student>
</Students>
</Section>
</Sections>
</Class>
Advantages
Following are the advantages provided by XML −
Technology agnostic − Being plain text, XML is technology independent. It can be used by any technology for data storage and transmission purpose.
Human readable − XML uses simple text format. It is human readable and understandable.
Extensible − In XML, custom tags can be created and used very easily.
Allow Validation − Using XSD, DTD and XML structure can be validated easily.
Disadvantages
Following are the disadvantages of XML usage −
Redundant Syntax − Normally XML file contains numerous repetitive terms.
Verbose − Being a verbose language, XML file size increases the transmission and storage costs.
Apache Xerces - Environment Setup
This chapter will guide you on how to prepare a development environment to start your work with Xerces Capabilities. It will also teach you how to set up JDK on your machine before you set up spring −
Setup Java Development Kit (JDK)
You can download the latest version of SDK from Oracle's Java site − Java SE Downloads. You will find instructions for installing JDK in downloaded files, follow the given instructions to install and configure the setup. Finally set PATH and JAVA_HOME environment variables to refer to the directory that contains java and javac, typically java_install_dir/bin and java_install_dir respectively.
If you are running Windows and have installed the JDK in C:\jdk-24, you would have to put the following line in your C:\autoexec.bat file.
set PATH=C:\jdk-24;%PATH% set JAVA_HOME=C:\jdk-24
Alternatively, on Windows NT/2000/XP, you will have to right-click on My Computer, select Properties → Advanced → Environment Variables. Then, you will have to update the PATH value and click the OK button.
On Unix (Solaris, Linux, etc.), if the SDK is installed in /usr/local/jdk-24 and you use the C shell, you will have to put the following into your .cshrc file.
setenv PATH /usr/local/jdk-24/bin:$PATH setenv JAVA_HOME /usr/local/jdk-24
Alternatively, if you use an Integrated Development Environment (IDE) like Borland JBuilder, Eclipse, IntelliJ IDEA, or Sun ONE Studio, you will have to compile and run a simple program to confirm that the IDE knows where you have installed Java. Otherwise, you will have to carry out a proper setup as given in the document of the IDE.
Popular Java Editors
To write your Java programs, you need a text editor. There are many sophisticated IDEs available in the market. But for now, you can consider one of the following −
Notepad − On Windows machine, you can use any simple text editor like Notepad (Recommended for this tutorial), TextPad.
Netbeans − It is a Java IDE that is open-source and free, which can be downloaded from www.netbeans.org/index.html.
Eclipse − It is also a Java IDE developed by the eclipse open-source community and can be downloaded from www.eclipse.org.
Install Eclipse
In this chapter, we will write examples using Eclipse IDE. Before proceeding with the installation, make sure that you already have Eclipse installed in your system. If not, download and install Eclipse.
For more information on Eclipse, please refer our Eclipse Tutorial
Set Maven
In this tutorial, we are using maven to run and build the xerces based examples. Follow the Maven - Environment Setup to install maven.
pom.xml
Following are the Xerces dependency used in this tutorial under pom.xml.
<dependency>
<groupId>xerces</groupId>
<artifactId>xercesImpl</artifactId>
<version>2.12.2</version>
</dependency>
Apache Xerces - XML Parsers
What is Apache Xerces2?
Xerces2 is a Java based processor and provides standard interfaces and implementations for following XML parsing API standards −
Document Object Model (DOM) Level 3
Simple API for XML (SAX) 2.0.2
Streaming API for XML (StAX) 1.0 Event API
Java APIs for XML Processing (JAXP) 1.4
What is XML Parsing?
Parsing XML refers to going through the XML document to access data or to modify data in one or the other way.
What is XML Parser?
XML Parser provides a way to access or modify the data present in an XML document. Java provides multiple options to parse XML document. Following are various types of parsers which are commonly used to parse XML documents.
Dom Parser − Parses the document by loading the complete contents of the document and creating its complete hierarchical tree in memory.
SAX Parser − Parses the document on event based triggers. Does not load the complete document into the memory.
StAX Parser − Parses the document in similar fashion to SAX parser but in a more efficient way.
Now, we will elaborate each parser using the Apache Xerces library in our subsequent chapters.
Apache Xerces - DOM Parser Overview
The Document Object Model is an official recommendation of the World Wide Web Consortium (W3C). It defines an interface that enables programs to access and update the style, structure, and contents of the XML documents. XML parsers that support the DOM, implement that interface.
When to use?
You should use a DOM parser when −
You need to know a lot about the structure of a document.
You need to move parts of the document around (you might want to sort certain elements, for example).
You need to use the information in the document more than once.
What you get?
When you parse an XML document with a DOM parser, you get back a tree structure that contains all of the elements of your document. The DOM provides a variety of functions you can use to examine the contents and structure of the document.
Advantages
The DOM is a common interface for manipulating document structures. One of its design goals is that the Java code written for one DOM-compliant parser should run on any other DOM-compliant parser without changes.
DOM interfaces
The DOM defines several Java interfaces. Here are the most common interfaces −
Node − The base datatype of the DOM.
Element − The vast majority of the objects you will deal with are Elements.
Attr − Represents an attribute of an element.
Text − The actual content of an Element or Attr.
Document − Represents the entire XML document. A Document object is often referred to as a DOM tree.
Common DOM methods
When you are working with the DOM, there are several methods that are used often −
Document.getDocumentElement() − Returns the root element of the document.
Node.getFirstChild() − Returns the first child of a given Node.
Node.getLastChild() − Returns the last child of a given Node.
Node.getNextSibling() − These methods return the next sibling of a given Node.
Node.getPreviousSibling() − These methods return the previous sibling of a given Node.
Node.getAttribute(attrName) − For a given Node, returns the attribute with the requested name.
Output
The above program will generate the following result −
Root element :class ---------------------------- Current Element :student Student roll no : 393 First Name : Dinkar Last Name : Kad Nick Name : Dinkar Marks : 85 Current Element :student Student roll no : 493 First Name : Vineet Last Name : Gupta Nick Name : Vinni Marks : 95 Current Element :student Student roll no : 593 First Name : Jasvir Last Name : Singh Nick Name : Jazz Marks : 90
DOM Parser - Query XML Document
Here is the input xml file we need to query −
input.txt
<?xml version = "1.0"?>
<cars>
<supercars company = "Ferrari">
<carname type = "formula one">Ferarri 101</carname>
<carname type = "sports car">Ferarri 201</carname>
<carname type = "sports car">Ferarri 301</carname>
</supercars>
<supercars company = "Lamborgini">
<carname>Lamborgini 001</carname>
<carname>Lamborgini 002</carname>
<carname>Lamborgini 003</carname>
</supercars>
<luxurycars company = "Benteley">
<carname>Benteley 1</carname>
<carname>Benteley 2</carname>
<carname>Benteley 3</carname>
</luxurycars>
</cars>
Example - Quering XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;
public class XercesDemo {
public static void main(String argv[]) {
try {
File inputFile = new File("input.txt");
DocumentBuilderFactory dbFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(inputFile);
doc.getDocumentElement().normalize();
System.out.print("Root element: ");
System.out.println(doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("supercars");
System.out.println("----------------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
System.out.println("\nCurrent Element :");
System.out.print(nNode.getNodeName());
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.print("company : ");
System.out.println(eElement.getAttribute("company"));
NodeList carNameList =
eElement.getElementsByTagName("carname");
for (int count = 0;
count < carNameList.getLength(); count++) {
Node node1 = carNameList.item(count);
if (node1.getNodeType() ==
Node.ELEMENT_NODE) {
Element car = (Element) node1;
System.out.print("car name : ");
System.out.println(car.getTextContent());
System.out.print("car type : ");
System.out.println(car.getAttribute("type"));
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output
The above program will generate the following result −
Root element: cars ---------------------------- Current Element : supercarscompany : Ferrari car name : Ferarri 101 car type : formula one car name : Ferarri 201 car type : sports car car name : Ferarri 301 car type : sports car Current Element : supercarscompany : Lamborgini car name : Lamborgini 001 car type : car name : Lamborgini 002 car type : car name : Lamborgini 003 car type :
DOM Parser - Creating XML Document
Here is xml file we need to create −
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?> <cars><supercars company = "Ferrari"> <carname type = "formula one">Ferrari 101</carname> <carname type = "sports">Ferrari 202</carname> </supercars></cars>
Example - Creating XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import java.io.File;
public class XercesDemo {
public static void main(String argv[]) {
try {
DocumentBuilderFactory dbFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder =
dbFactory.newDocumentBuilder();
Document doc = dBuilder.newDocument();
// root element
Element rootElement = doc.createElement("cars");
doc.appendChild(rootElement);
// supercars element
Element supercar = doc.createElement("supercars");
rootElement.appendChild(supercar);
// setting attribute to element
Attr attr = doc.createAttribute("company");
attr.setValue("Ferrari");
supercar.setAttributeNode(attr);
// carname element
Element carname = doc.createElement("carname");
Attr attrType = doc.createAttribute("type");
attrType.setValue("formula one");
carname.setAttributeNode(attrType);
carname.appendChild(
doc.createTextNode("Ferrari 101"));
supercar.appendChild(carname);
Element carname1 = doc.createElement("carname");
Attr attrType1 = doc.createAttribute("type");
attrType1.setValue("sports");
carname1.setAttributeNode(attrType1);
carname1.appendChild(
doc.createTextNode("Ferrari 202"));
supercar.appendChild(carname1);
// write the content into xml file
TransformerFactory transformerFactory =
TransformerFactory.newInstance();
Transformer transformer =
transformerFactory.newTransformer();
DOMSource source = new DOMSource(doc);
StreamResult result =
new StreamResult(new File("cars.xml"));
transformer.transform(source, result);
// Output to console for testing
StreamResult consoleResult =
new StreamResult(System.out);
transformer.transform(source, consoleResult);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output
The above program will generate the following result −
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?> <cars><supercars company = "Ferrari"> <carname type = "formula one">Ferrari 101</carname> <carname type = "sports">Ferrari 202</carname> </supercars></cars>
DOM Parser - Modify XML Document
Here is xml file we need to modify −
input.txt
<?xml version = "1.0" encoding = "UTF-8" standalone = "no"?>
<cars>
<supercars company = "Ferrari">
<carname type = "formula one">Ferrari 101</carname>
<carname type = "sports">Ferrari 202</carname>
</supercars>
<luxurycars company = "Benteley">
<carname>Benteley 1</carname>
<carname>Benteley 2</carname>
<carname>Benteley 3</carname>
</luxurycars>
</cars>
Example - Modifying XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import java.io.File;
public class XercesDemo {
public static void main(String argv[]) {
try {
DocumentBuilderFactory dbFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder =
dbFactory.newDocumentBuilder();
Document doc = dBuilder.newDocument();
// root element
Element rootElement = doc.createElement("cars");
doc.appendChild(rootElement);
// supercars element
Element supercar = doc.createElement("supercars");
rootElement.appendChild(supercar);
// setting attribute to element
Attr attr = doc.createAttribute("company");
attr.setValue("Ferrari");
supercar.setAttributeNode(attr);
// carname element
Element carname = doc.createElement("carname");
Attr attrType = doc.createAttribute("type");
attrType.setValue("formula one");
carname.setAttributeNode(attrType);
carname.appendChild(
doc.createTextNode("Ferrari 101"));
supercar.appendChild(carname);
Element carname1 = doc.createElement("carname");
Attr attrType1 = doc.createAttribute("type");
attrType1.setValue("sports");
carname1.setAttributeNode(attrType1);
carname1.appendChild(
doc.createTextNode("Ferrari 202"));
supercar.appendChild(carname1);
// write the content into xml file
TransformerFactory transformerFactory =
TransformerFactory.newInstance();
Transformer transformer =
transformerFactory.newTransformer();
DOMSource source = new DOMSource(doc);
StreamResult result =
new StreamResult(new File("cars.xml"));
transformer.transform(source, result);
// Output to console for testing
StreamResult consoleResult =
new StreamResult(System.out);
transformer.transform(source, consoleResult);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output
The above program will generate the following result −
-----------Modified File----------- <?xml version = "1.0" encoding = "UTF-8" standalone = "no"?> <cars> <supercars company = "Lamborigini"> <carname type = "formula one">Lamborigini 001</carname> <carname type = "sports">Lamborigini 002</carname> </supercars></cars>
SAX Parser - Overview
SAX (the Simple API for XML) is an event-based parser for xml documents. Unlike a DOM parser, a SAX parser creates no parse tree. SAX is a streaming interface for XML, which means that applications using SAX receive event notifications about the XML document being processed - an element, and attribute, at a time in sequential order starting at the top of the document, and ending with the closing of the ROOT element.
Reads an XML document from top to bottom, recognizing the tokens that make up a well-formed XML document.
Tokens are processed in the same order as they appear in the document.
Reports the application program, the nature of tokens that the parser has encountered as they occur.
The application program provides an "event" handler that must be registered with the parser.
As the tokens are identified, the callback methods in the handler are invoked with the relevant information.
When to use?
You should use a SAX parser when −
You can process the XML document in a linear fashion from top to bottom.
The document is not deeply nested.
You are processing a very large XML document the DOM tree of which will consume a lot of memory. Typical DOM implementations use ten bytes of memory to represent one byte of XML.
The problem to be solved involves only part of the XML document.
Data is available as soon as it is seen by the parser, so SAX works well for an XML document that arrives over a stream.
Disadvantages of SAX
We have no random access to an XML document since it is processed in a forwardonly manner.
If you need to keep track of data the parser has seen or change the order of items, you must write the code and store the data on your own.
ContentHandler Interface
This interface specifies the callback methods that the SAX parser uses to notify an application program of the components of the XML document that it has seen.
void startDocument() − Called at the beginning of a document.
void endDocument() − Called at the beginning of a document.
void startElement(String uri, String localName, String qName, Attributes atts) − Called at the beginning of an element.
void endElement(String uri, String localName,String qName) − Called at the end of an element.
void characters(char[] ch, int start, int length) − Called when the character data is encountered.
void ignorableWhitespace( char[] ch, int start, int length) − Called when a DTD is present and ignorable whitespace is encountered.
void processingInstruction(String target, String data) − Called when a processing instruction is recognized.
void setDocumentLocator(Locator locator)) − Provides a Locator that can be used to identify positions in the document.
void skippedEntity(String name) − Called when an unresolved entity is encountered.
void startPrefixMapping(String prefix, String uri) − Called when a new namespace mapping is defined.
void endPrefixMapping(String prefix) − Called when a namespace definition ends its scope.
Attributes Interface
This interface specifies methods for processing the attributes connected to an element.
int getLength() − Returns the number of attributes.
String getQName(int index)
String getValue(int index)
String getValue(String qname)
SAX Parser - Parsing XML Document
Here is xml file we need to parse using SAX Parser −
input.txt
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Example - Parsing XML Document
UserHandler.java
package com.tutorialspoint.xml;
class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
String rollNo = attributes.getValue("rollno");
System.out.println("Roll No : " + rollNo);
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri,
String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[],
int start, int length) throws SAXException {
if (bFirstName) {
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
XercesDemo.java
package com.tutorialspoint.xml;
import java.io.File;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class XercesDemo {
public static void main(String[] args){
try {
File inputFile = new File("input.txt");
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
UserHandler userhandler = new UserHandler();
saxParser.parse(inputFile, userhandler);
} catch (Exception e) {
e.printStackTrace();
}
}
}
class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
String rollNo = attributes.getValue("rollno");
System.out.println("Roll No : " + rollNo);
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri,
String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[],
int start, int length) throws SAXException {
if (bFirstName) {
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
Output
The above program will generate the following result −
Roll No : 393 First Name: Dinkar Last Name: Kad Nick Name: Dinkar Marks: 85 End Element :student Roll No : 493 First Name: Vineet Last Name: Gupta Nick Name: Vinni Marks: 95 End Element :student Roll No : 593 First Name: Jasvir Last Name: Singh Nick Name: Jazz Marks: 90 End Element :student
SAX Parser - Quering XML Document
Here is xml file we need to query for roll no: 393 using SAX Parser −
input.txt
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Example - Parsing XML Document
UserHandler.java
class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
String rollNo = attributes.getValue("rollno");
System.out.println("Roll No : " + rollNo);
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri,
String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[],
int start, int length) throws SAXException {
if (bFirstName) {
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
XercesDemo.java
package com.tutorialspoint.xml;
import java.io.File;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class XercesDemo {
public static void main(String[] args){
try {
File inputFile = new File("input.txt");
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
UserHandler userhandler = new UserHandler();
saxParser.parse(inputFile, userhandler);
} catch (Exception e) {
e.printStackTrace();
}
}
}
class UserHandler extends DefaultHandler {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
String rollNo = null;
@Override
public void startElement(String uri,
String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
rollNo = attributes.getValue("rollno");
}
if(("393").equals(rollNo) &&
qName.equalsIgnoreCase("student")){
System.out.println("Start Element :" + qName);
}
if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
}
@Override
public void endElement(String uri,
String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("student")) {
if(("393").equals(rollNo)
&& qName.equalsIgnoreCase("student"))
System.out.println("End Element :" + qName);
}
}
@Override
public void characters(char ch[], int start, int length) throws SAXException {
if (bFirstName && ("393").equals(rollNo)) {
//age element, set Employee age
System.out.println("First Name: " + new String(ch, start, length));
bFirstName = false;
} else if (bLastName && ("393").equals(rollNo)) {
System.out.println("Last Name: " + new String(ch, start, length));
bLastName = false;
} else if (bNickName && ("393").equals(rollNo)) {
System.out.println("Nick Name: " + new String(ch, start, length));
bNickName = false;
} else if (bMarks && ("393").equals(rollNo)) {
System.out.println("Marks: " + new String(ch, start, length));
bMarks = false;
}
}
}
Output
The above program will generate the following result −
Start Element :student First Name: Dinkar Last Name: Kad Nick Name: Dinkar Marks: 85 End Element :student
SAX Parser - Create XML Document
It is better to use the StAX parser for creating XML than using the SAX parser. Please refer the Java StAX Parser section for the same.
SAX Parser - Modifying XML Document
Here is the input xml file we need to Modify by appending <Result>Pass<Result/> at the end of the </marks> tag. −
input.txt
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Example - Modifying XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import java.io.File;
import java.io.FileWriter;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.helpers.DefaultHandler;
public class XercesDemo extends DefaultHandler {
static String displayText[] = new String[1000];
static int numberLines = 0;
static String indentation = "";
public static void main(String args[]) {
try {
File inputFile = new File("input.txt");
SAXParserFactory factory =
SAXParserFactory.newInstance();
XercesDemo obj = new XercesDemo();
obj.childLoop(inputFile);
FileWriter filewriter = new FileWriter("newfile.xml");
for(int loopIndex = 0; loopIndex < numberLines; loopIndex++){
filewriter.write(displayText[loopIndex].toCharArray());
filewriter.write('\n');
System.out.println(displayText[loopIndex].toString());
}
filewriter.close();
} catch (Exception e) {
e.printStackTrace(System.err);
}
}
public void childLoop(File input){
DefaultHandler handler = this;
SAXParserFactory factory = SAXParserFactory.newInstance();
try {
SAXParser saxParser = factory.newSAXParser();
saxParser.parse(input, handler);
} catch (Throwable t) {}
}
public void startDocument() {
displayText[numberLines] = indentation;
displayText[numberLines] += "<?xml version=\"1.0\" encoding=\""+
"UTF-8" + "\"?>";
numberLines++;
}
public void processingInstruction(String target, String data) {
displayText[numberLines] = indentation;
displayText[numberLines] += "<?";
displayText[numberLines] += target;
if (data != null && data.length() > 0) {
displayText[numberLines] += ' ';
displayText[numberLines] += data;
}
displayText[numberLines] += "?>";
numberLines++;
}
public void startElement(String uri, String localName,
String qualifiedName, Attributes attributes) {
displayText[numberLines] = indentation;
indentation += " ";
displayText[numberLines] += '<';
displayText[numberLines] += qualifiedName;
if (attributes != null) {
int numberAttributes = attributes.getLength();
for (int loopIndex = 0; loopIndex < numberAttributes;
loopIndex++){
displayText[numberLines] += ' ';
displayText[numberLines] += attributes.getQName(loopIndex);
displayText[numberLines] += "=\"";
displayText[numberLines] += attributes.getValue(loopIndex);
displayText[numberLines] += '"';
}
}
displayText[numberLines] += '>';
numberLines++;
}
public void characters(char characters[], int start, int length) {
String characterData = (new String(characters, start, length)).trim();
if(characterData.indexOf("\n") < 0 && characterData.length() > 0) {
displayText[numberLines] = indentation;
displayText[numberLines] += characterData;
numberLines++;
}
}
public void endElement(String uri, String localName, String qualifiedName) {
indentation = indentation.substring(0, indentation.length() - 4);
displayText[numberLines] = indentation;
displayText[numberLines] += "</";
displayText[numberLines] += qualifiedName;
displayText[numberLines] += '>';
numberLines++;
if (qualifiedName.equals("marks")) {
startElement("", "Result", "Result", null);
characters("Pass".toCharArray(), 0, "Pass".length());
endElement("", "Result", "Result");
}
}
}
Output
The above program will generate the following result −
<class>
<student rollno = "393">
<firstname>
Dinkar
</firstname>
<lastname>
Kad
</lastname>
<nickname>
Dinkar
</nickname>
<marks>
85
</marks>
<Result>
Pass
</Result>
</student>
<student rollno = "493">
<firstname>
Vineet
</firstname>
<lastname>
Gupta
</lastname>
<nickname>
Vinni
</nickname>
<marks>
95
</marks>
<Result>
Pass
</Result>
</student>
<student rollno = "593">
<firstname>
Jasvir
</firstname>
<lastname>
Singh
</lastname>
<nickname>
Jazz
</nickname>
<marks>
90
</marks>
<Result>
Pass
</Result>
</student>
</class>
StAX Parser - Overview
StAX is a JAVA based API to parse XML document in a similar way as SAX parser does. But there are two major points of difference between the two APIs −
StAX is a PULL API whereas, SAX is a PUSH API. It means in case of StAX parser, the client application needs to ask the StAX parser to get information from XML whenever it needs but in case of the SAX parser, client application is required to get information when the SAX parser notifies the client application that information is available.
StAX API can read as well as write XML documents. Using SAX API, xml can be only read.
Following are the features of StAX API −
Reads an XML document from top to bottom, recognizing the tokens that make up a well-formed XML document.
Tokens are processed in the same order as they appear in the document.
Reports the application program on the nature of tokens that the parser has encountered as they occur.
The application program provides an "event" reader which acts as an iterator and iterates over the event to get the required information. Another reader available is the "cursor" reader which acts as a pointer to xml nodes.
As the events are identified, xml elements can be retrieved from the event object and can be processed further.
When to use?
You should use a StAX parser when −
You can process the XML document in a linear fashion from top to bottom.
The document is not deeply nested.
You are processing a very large XML document the DOM tree of which will consume too much memory. Typical DOM implementations use ten bytes of memory to represent one byte of XML.
The problem to be solved involves only part of the XML document.
Data is available as soon as it is seen by the parser, so StAX works well for an XML document that arrives over a stream.
Disadvantages of SAX
We have no random access to an XML document since it is processed in a forward-only manner.
If you need to keep track of data the parser has seen or change the order of items, you must write the code and store the data on your own.
XMLEventReader Class
This class provides the iterator of events which can be used to iterate over events as they occur while parsing the XML document
StartElement asStartElement() − Used to retrieve value and attributes of element.
EndElement asEndElement() − Called at the end of an element.
Characters asCharacters() − Can be used to obtain characters such as CDATA, whitespace, etc.
XMLEventWriter Class
This interface specifies methods for creating an event.
add(Event event) − Adds event containing elements to XML.
XMLStreamReader Class
This class provide iterator of events which can be used to iterate over events as they occur while parsing the XML document
int next() − Used to retrieve next event.
boolean hasNext() − Used to check further events exists or not
String getText() − Used to get text of an element
String getLocalName() − Used to get name of an element
XMLStreamWriter Class
This interface specifies methods for creating an event.
writeStartElement(String localName) − Adds start element of a given name.
writeEndElement(String localName) − Adds end element of a given name.
writeAttribute(String localName, String value) − Writes attribute to an element.
StAX Parser - Parsing XML Document
Here is the input xml file we need to parse −
input.txt
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Example - Parsing XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Iterator;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
public class XercesDemo {
public static void main(String[] args) {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
try {
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLEventReader eventReader =
factory.createXMLEventReader(new FileReader("input.txt"));
while(eventReader.hasNext()){
XMLEvent event = eventReader.nextEvent();
switch(event.getEventType()){
case XMLStreamConstants.START_ELEMENT:
StartElement startElement = event.asStartElement();
String qName = startElement.getName().getLocalPart();
if (qName.equalsIgnoreCase("student")) {
System.out.println("Start Element : student");
Iterator<Attribute> attributes = startElement.getAttributes();
String rollNo = attributes.next().getValue();
System.out.println("Roll No : " + rollNo);
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
break;
case XMLStreamConstants.CHARACTERS:
Characters characters = event.asCharacters();
if(bFirstName){
System.out.println("First Name: " + characters.getData());
bFirstName = false;
}
if(bLastName){
System.out.println("Last Name: " + characters.getData());
bLastName = false;
}
if(bNickName){
System.out.println("Nick Name: " + characters.getData());
bNickName = false;
}
if(bMarks){
System.out.println("Marks: " + characters.getData());
bMarks = false;
}
break;
case XMLStreamConstants.END_ELEMENT:
EndElement endElement = event.asEndElement();
if(endElement.getName().getLocalPart().equalsIgnoreCase("student")){
System.out.println("End Element : student");
System.out.println();
}
break;
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
}
}
}
Output
The above program will generate the following result −
Start Element : student Roll No : 393 First Name: Dinkar Last Name: Kad Nick Name: Dinkar Marks: 85 End Element : student Start Element : student Roll No : 493 First Name: Vineet Last Name: Gupta Nick Name: Vinni Marks: 95 End Element : student Start Element : student Roll No : 593 First Name: Jasvir Last Name: Singh Nick Name: Jazz Marks: 90 End Element : student
StAX Parser - Quering XML Document
Here is the input xml file we need to query −
input.txt
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Example - Parsing XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Iterator;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
public class XercesDemo {
public static void main(String[] args) {
boolean bFirstName = false;
boolean bLastName = false;
boolean bNickName = false;
boolean bMarks = false;
boolean isRequestRollNo = false;
try {
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLEventReader eventReader = factory.createXMLEventReader(
new FileReader("input.txt"));
String requestedRollNo = "393";
while(eventReader.hasNext()){
XMLEvent event = eventReader.nextEvent();
switch(event.getEventType()){
case XMLStreamConstants.START_ELEMENT:
StartElement startElement = event.asStartElement();
String qName = startElement.getName().getLocalPart();
if (qName.equalsIgnoreCase("student")) {
Iterator<Attribute> attributes = startElement.getAttributes();
String rollNo = attributes.next().getValue();
if(rollNo.equalsIgnoreCase(requestedRollNo)){
System.out.println("Start Element : student");
System.out.println("Roll No : " + rollNo);
isRequestRollNo = true;
}
} else if (qName.equalsIgnoreCase("firstname")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastname")) {
bLastName = true;
} else if (qName.equalsIgnoreCase("nickname")) {
bNickName = true;
} else if (qName.equalsIgnoreCase("marks")) {
bMarks = true;
}
break;
case XMLStreamConstants.CHARACTERS:
Characters characters = event.asCharacters();
if(bFirstName && isRequestRollNo){
System.out.println("First Name: " + characters.getData());
bFirstName = false;
}
if(bLastName && isRequestRollNo){
System.out.println("Last Name: " + characters.getData());
bLastName = false;
}
if(bNickName && isRequestRollNo){
System.out.println("Nick Name: " + characters.getData());
bNickName = false;
}
if(bMarks && isRequestRollNo){
System.out.println("Marks: " + characters.getData());
bMarks = false;
}
break;
case XMLStreamConstants.END_ELEMENT:
EndElement endElement = event.asEndElement();
if(endElement.getName().getLocalPart().equalsIgnoreCase("student") && isRequestRollNo){
System.out.println("End Element : student");
System.out.println();
isRequestRollNo = false;
}
break;
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
}
}
}
Output
The above program will generate the following result −
Start Element : student Roll No : 393 First Name: Dinkar Last Name: Kad Nick Name: Dinkar Marks: 85 End Element : student
StAX Parser - Creating a XML Document
Here is the XML we need to create −
<?xml version = "1.0" ?>
<cars>
<supercars company = "Ferrari">
<carname type = "formula one">Ferrari 101</carname>
<carname type = "sports">Ferrari 202</carname>
</supercars>
</cars>
Example - Creating XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import java.io.IOException;
import java.io.StringWriter;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;
public class XercesDemo {
public static void main(String[] args) {
try {
StringWriter stringWriter = new StringWriter();
XMLOutputFactory xMLOutputFactory = XMLOutputFactory.newInstance();
XMLStreamWriter xMLStreamWriter = xMLOutputFactory.createXMLStreamWriter(stringWriter);
xMLStreamWriter.writeStartDocument();
xMLStreamWriter.writeStartElement("cars");
xMLStreamWriter.writeStartElement("supercars");
xMLStreamWriter.writeAttribute("company", "Ferrari");
xMLStreamWriter.writeStartElement("carname");
xMLStreamWriter.writeAttribute("type", "formula one");
xMLStreamWriter.writeCharacters("Ferrari 101");
xMLStreamWriter.writeEndElement();
xMLStreamWriter.writeStartElement("carname");
xMLStreamWriter.writeAttribute("type", "sports");
xMLStreamWriter.writeCharacters("Ferrari 202");
xMLStreamWriter.writeEndElement();
xMLStreamWriter.writeEndElement();
xMLStreamWriter.writeEndDocument();
xMLStreamWriter.flush();
xMLStreamWriter.close();
String xmlString = stringWriter.getBuffer().toString();
stringWriter.close();
System.out.println(xmlString);
} catch (XMLStreamException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Output
The above program will generate the following result −
<?xml version = "1.0" ?> <cars>< supercars company = "Ferrari"> <carname type = "formula one">Ferrari 101</carname> <carname type = "sports">Ferrari 202</carname> </supercars> </cars>
StAX Parser - Modifying a XML Document
Here is the XML we need to create −
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>Dinkar</firstname>
<lastname>Kad</lastname>
<nickname>Dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vineet</firstname>
<lastname>Gupta</lastname>
<nickname>Vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>Jasvir</firstname>
<lastname>Singh</lastname>
<nickname>Jazz</nickname>
<marks>90</marks>
</student>
</class>
Example - Modifying XML Document
XercesDemo.java
package com.tutorialspoint.xml;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;
public class XercesDemo {
public static void main(String[] args) {
try {
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLEventReader eventReader = factory.createXMLEventReader(
new FileReader("input.txt"));
SAXBuilder saxBuilder = new SAXBuilder();
Document document = saxBuilder.build(new File("input.txt"));
Element rootElement = document.getRootElement();
List<Element> studentElements = rootElement.getChildren("student");
while(eventReader.hasNext()){
XMLEvent event = eventReader.nextEvent();
switch(event.getEventType()){
case XMLStreamConstants.START_ELEMENT:
StartElement startElement = event.asStartElement();
String qName = startElement.getName().getLocalPart();
if (qName.equalsIgnoreCase("student")) {
Iterator<Attribute> attributes = startElement.getAttributes();
String rollNo = attributes.next().getValue();
if(rollNo.equalsIgnoreCase("393")){
//get the student with roll no 393
for(int i=0;i < studentElements.size();i++){
Element studentElement = studentElements.get(i);
if(studentElement.getAttribute("rollno").getValue().equalsIgnoreCase("393")){
studentElement.removeChild("marks");
studentElement.addContent(new Element("marks").setText("80"));
}
}
}
}
break;
}
}
XMLOutputter xmlOutput = new XMLOutputter();
// display xml
xmlOutput.setFormat(Format.getPrettyFormat());
xmlOutput.output(document, System.out);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
} catch (JDOMException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
The above program will generate the following result −
<?xml version = "1.0" ?> <student rollno = "393"> <firstname>Dinkar</firstname> <lastname>Kad</lastname> <nickname>Dinkar</nickname> <marks>80</marks> </student> <student rollno = "493"> <firstname>Vineet</firstname> <lastname>Gupta</lastname> <nickname>Vinni</nickname> <marks>95</marks> </student> <student rollno = "593"> <firstname>Jasvir</firstname> <lastname>Singh</lastname> <nickname>Jazz</nickname> <marks>90</marks> </student>