Accessing data using XPATH in a XML file

We can learn 2 different ways of creating document object (getXmlParser() , getXmlParsers() ) and accessing the data from xml file using XPATH.

Error.xml
<?xml version="1.0" encoding="UTF-8"?>
<EXCEPTION_ROOT>
<EXCEPTION CODE="BENEF_1000">
<EXCEPTION_MESSAGE>
Beneficiary is not saved
</EXCEPTION_MESSAGE>
</EXCEPTION>
<EXCEPTION CODE="BENEF_1001">
<EXCEPTION_MESSAGE>
No records found
</EXCEPTION_MESSAGE>
</EXCEPTION>
</EXCEPTION_ROOT>

Error.xml
import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.apache.xerces.parsers.DOMParser;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import org.w3c.dom.Document;

public class Error {

private static Document doc;
private static DOMParser objDOMParser = null;
private static String fileName = "Error.xml";

public static void main(String[] args){

Error err1 = new Error();
err1.getXmlParsers();

err1.getSQLQuery("BENEF_1000");

Error err2 = new Error();
err2.getXmlParser();

err2.getSQLQuery("BENEF_1001");
}
public void getXmlParsers() {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

try {
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream objInputStream = this.getClass().getResourceAsStream(fileName);
doc = builder.parse(objInputStream);
}catch(ParserConfigurationException parserException) {
}catch(SAXException saxException) {
}catch(IOException ioException) {
}catch(Exception exception){}
}
public void getXmlParser() {
try {
InputStream is = this.getClass().getResourceAsStream(fileName);
org.xml.sax.InputSource isrc = new org.xml.sax.InputSource(is);
objDOMParser = new DOMParser();
objDOMParser.parse(isrc);
doc = objDOMParser.getDocument();
} catch (Exception e) {
System.err.println(e);
}
}

public static void getSQLQuery(String queryName) {
String errorMessage = null;
try{
XPathFactory xpathFactory = XPathFactory.newInstance();
XPath xpath = xpathFactory.newXPath();
String expression ="EXCEPTION_ROOT/EXCEPTION[@CODE='"+queryName+"']/EXCEPTION_MESSAGE/text()";
XPathExpression expr = xpath.compile(expression);
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
errorMessage = nodes.item(0).getNodeValue();
System.out.println(errorMessage);
}
catch(Exception ex) {
ex.printStackTrace();
System.out.println("......Error while parsing.....");
}
}
}

Accessing an XML document to retrieve attribute values

Requirement:

We have an XML file with a element and couple of attributes in it. We need to parse the XML file and retrieve only the attribute values.

XML File (ABCSQLQueries):

<ABCQUERIES
TBUUSLIST_QUERY="SELECT TBUISUSKEY,TBUISUSNAME FROM OWN_ABC.TBUISUSLABELS"
AVAILABLEWITH_QUERY="SELECT A.REQUESTAVAILABLEKEY, A.DISPLAY FROM OWN_ABC.REQUESTAVAILABLE A, OWN_ABC.REQUESTDETAILS
B WHERE B.REQUESTDETAILSKEY = ? AND A.REQUESTAVAILABLEKEY = B.REQUESTAVAILABLEKEY"
/>

Code:

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.xml.sax.SAXException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Attr;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;


public class XmlReading {

Document doc;
Element element;
private static String fileName = "ABCSQLQueries.xml";

public static void main(String[] args) {
XmlReading xr = new XmlReading();
// xr.getXmlParser();
xr.getXmlParser(args);
}


public void getXmlParser() {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

try {
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream objInputStream = this.getClass().getResourceAsStream(fileName);
doc = builder.parse(objInputStream);
}catch(ParserConfigurationException parserException) {
}catch(SAXException saxException) {
}catch(IOException ioException) {
}catch(Exception exception){}

getAttributes();
}


public void getXmlParser(String[] args) {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

if(args.length != 1) {
System.err.println("XML File Required");
}

try {
DocumentBuilder builder = factory.newDocumentBuilder();
doc = builder.parse(new File(args[0]));
}catch(ParserConfigurationException e1) {
}catch(SAXException e2) {
}catch(IOException e3) {
}
getAttributes();
}

public void getAttributes() {

// Retrive the entire Document from the Dom Tree
element = doc.getDocumentElement();
// Retrive the attribute list from document
NamedNodeMap attrs = element.getAttributes();

// Get number of attributes in the element
int numAttrs = attrs.getLength();
System.out.println("\n Number of Attribute: " + numAttrs + "\n");

// Process each attribute

for (int i=0; i<numAttrs; i++) {
Node node = attrs.item(i);
// Get attribute name and value
String attrName = node.getNodeName();
String attrValue = node.getNodeValue();
System.out.println("Attribute Name: " + attrName + "\nAttribute Value: " + attrValue + "\n");
}

}
}

XML parsing has been done in both ways like user can give the XML file as input through console as well as hard-code the XML file name directly in the parsing java file.

Accessing an XML document to retrieve element values

Requirement:

We have an XML file with couple of elements wrapped in a parent element. We need to parse the XML file and retrieve only the child element values.

XML File (ABCSQLQueries):

<ABCQUERIES>
<TBUUSLIST_QUERY>
SELECT TBUISUSKEY,TBUISUSNAME FROM OWN_ABC.TBUISUSLABELS
</TBUUSLIST_QUERY>
<AVAILABLEWITH_QUERY>
SELECT A.REQUESTAVAILABLEKEY, A.DISPLAY FROM OWN_ ABC.REQUESTAVAILABLE A, OWN_ ABC.REQUESTDETAILS B WHERE B.REQUESTDETAILSKEY = ? AND A.REQUESTAVAILABLEKEY = B.REQUESTAVAILABLEKEY
</AVAILABLEWITH_QUERY>
</ABCQUERIES>

Code:

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Attr;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

import org.xml.sax.SAXException;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;

public class XmlReading {

Document doc;
Element element;
private static String fileName = "ABCSQLQueries.xml";


public static void main(String[] args) {
XmlReading xr = new XmlReading();
xr.getXmlParser();
// xr.getXmlParser(args);
}

public void getXmlParser() {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

try {
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream objInputStream = this.getClass().getResourceAsStream(fileName);
doc = builder.parse(objInputStream);
}catch(ParserConfigurationException parserException) {
}catch(SAXException saxException) {
}catch(IOException ioException) {
}catch(Exception exception){}

getAttributes();
}

public void getXmlParser(String[] args) {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

if(args.length != 1) {
System.err.println("XML File Required");
}

try {
DocumentBuilder builder = factory.newDocumentBuilder();
doc = builder.parse(new File(args[0]));
}catch(ParserConfigurationException e1) {
}catch(SAXException e2) {
}catch(IOException e3) {
}
getAttributes();
}

public void getAttributes() {

// Retrive the entire Document from the Dom Tree
element = doc.getDocumentElement();
String s1 = element.getTagName();
System.out.println("\nRoot Tag Name: " + s1);

// To get all the elements in a DOM Tree
NodeList nl1 = element.getElementsByTagName("*");
int i2 = nl1.getLength();
System.out.println("No of Elements: " + i2 + "\n");
for(int i=0; i<i2; i++) {
Node node = nl1.item(i);

System.out.println("Node Name: " + node.getNodeName());
System.out.println("Node Value: " + node.getFirstChild().getNodeValue());
}

}
}

XML parsing has been done in both ways like user can give the XML file as input through console as well as hard-code the XML file name directly in the parsing java file.

Accessing an XML document using DOM

Requirement:
We have a completely organized XML file with SQL Queries. We need to parse the XML file and retrieve only the SQL Queries based on module code and sql query id.


XML File (ABCSQLQueries):


<SQL_ROOT>
<MODULE CODE="REQUEST">
<SQL_SEQMENT ID="PAYMENTTERMS_QUERY">
SELECT A.PAYMENTTERMSKEY, A.DISPLAY FROM OWN_ABC.PAYMENTTERMS A, OWN_ABC.REQUESTDETAILS B WHERE
B.REQUESTDETAILSKEY = ? AND A.PAYMENTTERMSKEY = B.PAYMENTTERMSKEY
</SQL_SEQMENT>
<SQL_SEQMENT ID="REQUEST_UPDATE">
update request query
</SQL_SEQMENT>
</MODULE>
<MODULE CODE="BANK">
<SQL_SEQMENT ID="BANK_SELECT">
Select bank query
</SQL_SEQMENT>
<SQL_SEQMENT ID="BANK_UPDATE">
update bank query
</SQL_SEQMENT>
</MODULE>
<MODULE CODE="COUNTRY">
<SQL_SEQMENT ID="COUNTRY_SELECT">
Select country query
</SQL_SEQMENT>
<SQL_SEQMENT ID="COUNTRY_UPDATE">
update country query
</SQL_SEQMENT>
</MODULE>
</SQL_ROOT>

Code:

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Attr;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

import org.xml.sax.SAXException;

import java.io.InputStream;
import java.io.IOException;

public class XMLParsing {

static Document doc;
static Element element;
private static String fileName = "ABCSQLQueries.xml";

public static void main(String[] args) {
XMLParsing xr = new XMLParsing();
xr.getXmlParser();
}

public void getXmlParser() {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

try {
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream is = this.getClass().getResourceAsStream(fileName);
doc = builder.parse(is);
}catch(ParserConfigurationException parserException) {
}catch(SAXException saxException) {
}catch(IOException ioException) {
}catch(Exception exception){}
getElements("REQUEST", "PAYMENTTERMS_QUERY");
}

public static String getElements(String moduleName, String queryName) {

String gtemQuery = null;
// Retrive the entire Document from the Dom Tree
element = doc.getDocumentElement();
String s1 = element.getTagName();
System.out.println("\nRoot Tag Name: " + s1);

NodeList parentNodeList = element.getElementsByTagName("MODULE");

for(int parentNode = 0; parentNode < parentNodeList.getLength(); parentNode++) {
Node queryNode = parentNodeList.item(parentNode);

String attributeValue = getAttributes(queryNode);

if(queryNode.getNodeName().equals("MODULE") && attributeValue.equals(moduleName)) {

NodeList childNodeList = queryNode.getChildNodes();

for(int i=0; i<childNodeList.getLength(); i++) {
String childAttributeValue = null;

Node childNode = childNodeList.item(i);

if(childNode.getNodeType() == Node.ELEMENT_NODE){
childAttributeValue = getAttributes(childNode);

if(childAttributeValue.trim().equals(queryName)){
System.out.println("Query: " + childNode.getTextContent().trim());
gtemQuery = childNode.getTextContent().trim();
break;
}
}
}
}
}
return gtemQuery;
}

public static String getAttributes(Node firstLevelNode) {

String attributeValue = null;

NamedNodeMap nodeMap = firstLevelNode.getAttributes();

for (int i=0; i<nodeMap.getLength(); i++) {
Node attributeNode = nodeMap.item(i);
// Get attribute value
attributeValue = attributeNode.getNodeValue();
System.out.println("Attribute Value: " + attributeValue );
}
return attributeValue;
}

}

Accessing an XML document using XPATH

Requirement:
We have a completely organized XML file with SQL Queries. We need to parse the XML file and retrieve only the SQL Queries based on module code and sql query id.


XML File (ABCSQLQueries):

<SQL_ROOT>
<MODULE CODE="REQUEST">
<SQL_SEQMENT ID="PAYMENTTERMS_QUERY">
SELECT A.PAYMENTTERMSKEY, A.DISPLAY FROM OWN_ABC.PAYMENTTERMS A, OWN_ABC.REQUESTDETAILS B WHERE
B.REQUESTDETAILSKEY = ? AND A.PAYMENTTERMSKEY = B.PAYMENTTERMSKEY
</SQL_SEQMENT>
<SQL_SEQMENT ID="REQUEST_UPDATE">
update request query
</SQL_SEQMENT>
</MODULE>
<MODULE CODE="BANK">
<SQL_SEQMENT ID="BANK_SELECT">
Select bank query
</SQL_SEQMENT>
<SQL_SEQMENT ID="BANK_UPDATE">
update bank query
</SQL_SEQMENT>
</MODULE>
<MODULE CODE="COUNTRY">
<SQL_SEQMENT ID="COUNTRY_SELECT">
Select country query
</SQL_SEQMENT>
<SQL_SEQMENT ID="COUNTRY_UPDATE">
update country query
</SQL_SEQMENT>
</MODULE>
</SQL_ROOT>

Code:

import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

public class ABCSQLLoader {

static Document doc;
static Element element;
// Declare it in constants file and use it instead of hard-coding like this
private static String fileName = "ABCSQLQueries.xml";

Uncomment only for execution through console mode.
/*
public static void main(String[] args) {
XMLParser xr = new XMLParser();
xr.getXmlParser();
}
*/

public void getXmlParser() {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

try {
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream objInputStream = this.getClass().getResourceAsStream(fileName);
doc = builder.parse(objInputStream);
}catch(ParserConfigurationException parserException) {
}catch(SAXException saxException) {
}catch(IOException ioException) {
}catch(Exception exception){}

Uncomment only for execution through console mode.
//getSQLQuery("REQUEST", "PAYMENTTERMS_QUERY");
}

public static String getSQLQuery (String moduleName, String queryName) {
String sqlQuery = null;
try{
XPathFactory xpathFactory = XPathFactory.newInstance();
XPath xpath = xpathFactory.newXPath();
String expression ="SQL_ROOT/MODULE[@CODE='"+moduleName+"']/SQL_SEQMENT[@ID='"+queryName+"']/text()";
XPathExpression expr = xpath.compile(expression);
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
sqlQuery = nodes.item(0).getNodeValue();
System.out.println("Query: " + sqlQuery);
}
catch(Exception ex) {
System.out.println("......Error while parsing.....");
}
return sqlQuery;
}
}

How to apply this whole XML-SQL concept in a J2EE application?


Step-I: Load the XMLParser (ABCSQLLoader) while the J2EE web application starts in the server through a servlet’s init method.

public class PopulateApplicationDataServlet extends HttpServlet {

public void init(ServletConfig config) throws ServletException {
XMLParser parsing = new XMLParser();
parsing.getXmlParser();

}
}

Step-II:
Once the xml parser parse’s the XML file, give the module name and query name as parameters through normal java method call from the application DAO classes.

objResultSet = objStatement.executeQuery(ABCSQLLoader.getSQLQuery(
"REQUEST", " PAYMENTTERMS_QUERY "));

XQuery Tutorial

XQuery Tutorial

How to restrict null values in XML tags

The following declartion will restrict the tag values to only a to z, A to Z and 1 to 9 and no other values can be entered into it.

<element name="first">
<simpleType>
<restriction base="string">
<pattern value="([a-zA-Z1-9])+"/>
</restriction>
</simpleType>
</element>

XML Document To Schema

The following article, "Validation by Instance", explores how one can translate an XML document into a Document Type Definition (DTD), a RELAX NG schema, and then into an W3C XML Schema (WXS) schema.

You can also use Stylus Studio Professional Edition (or) Stylus Studio Enterprise Edition XML Editor which integrates

XML instance Document to XML Schema
XML instance Document to DTD Schema

Articles

Here is a list of articles by Deepak Vohra.

XPath

Here is a XPath Tutorial from OnJava.com by Deepak Vohra.

XML Book

Processing XML with Java by Elliotte Rusty Harold

API [DOM, SAX, JAXP] Parsers[Crimson, Xerces] - How to relate all these

Here is a link from Processing XML with Java by Elliotte Rusty Harold which explains clearly about all the details of

1. What a parser is
2. what are the different API's with which you can access XML Document
3. What are the different parsers available to parse an XML Document

JAXP(SAX & DOM) vs JAXB

Find the discussion about it here

Web Services Acronyms

Here is a list of acronyms used in Web Services.

XML: Extensible Markup Language
SOAP: Simple Object Access Protocol
UDDI: Universal Description, Discovery and Integration
ebXML: Electronic Business Extensible Markup Language
WSDL: Web Services Description Language
JAXM: Java API for XML Messaging
JAX-RPC: Java API for Remote Procedure Call
JAXR: Java API for XML Registry
JAXP: Java API for XML Processing
JAXB: Java Architecture for XML Binding
SAAJ: SOAP with Attachments API for JavaJava
WSDP: Java Web Services Developer Pack
WS-I: Web Services Interoperability Organization
W3C: World Wide Web Consortium
OASIS: Organization for the Advancement of Structured Information Standards
JCP: Java Community Process

Java Architecture for XML Binding(JAXB)

JAXB Basic Tutorial

What is JAXB.

About JAXB.

JAXB API

JAXB FAQ

XML - Java Mapping Tools

Best practices for creating java classes from xml schema (.xsd)

1. Apache XMLBeans
2. (Java Architecture for XML Binding)JAXB/JaxMe

XML files to a Javabean

There are many tools out there which can be used to get the work done.

1. Jakarta Commons Digester.
2. Castor
3. XStream

While convert XML to Java objects when do you prefer Digestor over JAXB?

You can learn all about it here