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Create xml Elements and sub elements in Java using dom [duplicate]

I have to read and write to and from an XML file. What is the easiest way to read and write XML files using Java?

Here is a quick DOM example that shows how to read and write a simple xml file with its dtd:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE roles SYSTEM "roles.dtd">
<roles>
<role1>User</role1>
<role2>Author</role2>
<role3>Admin</role3>
<role4/>
</roles>
and the dtd:
<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT roles (role1,role2,role3,role4)>
<!ELEMENT role1 (#PCDATA)>
<!ELEMENT role2 (#PCDATA)>
<!ELEMENT role3 (#PCDATA)>
<!ELEMENT role4 (#PCDATA)>
First import these:
import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;
import org.xml.sax.*;
import org.w3c.dom.*;
Here are a few variables you will need:
private String role1 = null;
private String role2 = null;
private String role3 = null;
private String role4 = null;
private ArrayList<String> rolev;
Here is a reader (String xml is the name of your xml file):
public boolean readXML(String xml) {
rolev = new ArrayList<String>();
Document dom;
// Make an instance of the DocumentBuilderFactory
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
// use the factory to take an instance of the document builder
DocumentBuilder db = dbf.newDocumentBuilder();
// parse using the builder to get the DOM mapping of the
// XML file
dom = db.parse(xml);
Element doc = dom.getDocumentElement();
role1 = getTextValue(role1, doc, "role1");
if (role1 != null) {
if (!role1.isEmpty())
rolev.add(role1);
}
role2 = getTextValue(role2, doc, "role2");
if (role2 != null) {
if (!role2.isEmpty())
rolev.add(role2);
}
role3 = getTextValue(role3, doc, "role3");
if (role3 != null) {
if (!role3.isEmpty())
rolev.add(role3);
}
role4 = getTextValue(role4, doc, "role4");
if ( role4 != null) {
if (!role4.isEmpty())
rolev.add(role4);
}
return true;
} catch (ParserConfigurationException pce) {
System.out.println(pce.getMessage());
} catch (SAXException se) {
System.out.println(se.getMessage());
} catch (IOException ioe) {
System.err.println(ioe.getMessage());
}
return false;
}
And here a writer:
public void saveToXML(String xml) {
Document dom;
Element e = null;
// instance of a DocumentBuilderFactory
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
// use factory to get an instance of document builder
DocumentBuilder db = dbf.newDocumentBuilder();
// create instance of DOM
dom = db.newDocument();
// create the root element
Element rootEle = dom.createElement("roles");
// create data elements and place them under root
e = dom.createElement("role1");
e.appendChild(dom.createTextNode(role1));
rootEle.appendChild(e);
e = dom.createElement("role2");
e.appendChild(dom.createTextNode(role2));
rootEle.appendChild(e);
e = dom.createElement("role3");
e.appendChild(dom.createTextNode(role3));
rootEle.appendChild(e);
e = dom.createElement("role4");
e.appendChild(dom.createTextNode(role4));
rootEle.appendChild(e);
dom.appendChild(rootEle);
try {
Transformer tr = TransformerFactory.newInstance().newTransformer();
tr.setOutputProperty(OutputKeys.INDENT, "yes");
tr.setOutputProperty(OutputKeys.METHOD, "xml");
tr.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
tr.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, "roles.dtd");
tr.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
// send DOM to file
tr.transform(new DOMSource(dom),
new StreamResult(new FileOutputStream(xml)));
} catch (TransformerException te) {
System.out.println(te.getMessage());
} catch (IOException ioe) {
System.out.println(ioe.getMessage());
}
} catch (ParserConfigurationException pce) {
System.out.println("UsersXML: Error trying to instantiate DocumentBuilder " + pce);
}
}
getTextValue is here:
private String getTextValue(String def, Element doc, String tag) {
String value = def;
NodeList nl;
nl = doc.getElementsByTagName(tag);
if (nl.getLength() > 0 && nl.item(0).hasChildNodes()) {
value = nl.item(0).getFirstChild().getNodeValue();
}
return value;
}
Add a few accessors and mutators and you are done!

Writing XML using JAXB (Java Architecture for XML Binding):
http://www.mkyong.com/java/jaxb-hello-world-example/
package com.mkyong.core;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
#XmlRootElement
public class Customer {
String name;
int age;
int id;
public String getName() {
return name;
}
#XmlElement
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
#XmlElement
public void setAge(int age) {
this.age = age;
}
public int getId() {
return id;
}
#XmlAttribute
public void setId(int id) {
this.id = id;
}
}
package com.mkyong.core;
import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
public class JAXBExample {
public static void main(String[] args) {
Customer customer = new Customer();
customer.setId(100);
customer.setName("mkyong");
customer.setAge(29);
try {
File file = new File("C:\\file.xml");
JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);
Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
// output pretty printed
jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
jaxbMarshaller.marshal(customer, file);
jaxbMarshaller.marshal(customer, System.out);
} catch (JAXBException e) {
e.printStackTrace();
}
}
}

The above answer only deal with DOM parser (that normally reads the entire file in memory and parse it, what for a big file is a problem), you could use a SAX parser that uses less memory and is faster (anyway that depends on your code).
SAX parser callback some functions when it find a start of element, end of element, attribute, text between elements, etc, so it can parse the document and at the same time you
get what you need.
Some example code:
http://www.mkyong.com/java/how-to-read-xml-file-in-java-sax-parser/

The answers only cover DOM / SAX and a copy paste implementation of a JAXB example.
However, one big area of when you are using XML is missing. In many projects / programs there is a need to store / retrieve some basic data structures. Your program has already a classes for your nice and shiny business objects / data structures, you just want a comfortable way to convert this data to a XML structure so you can do more magic on it (store, load, send, manipulate with XSLT).
This is where XStream shines. You simply annotate the classes holding your data, or if you do not want to change those classes, you configure a XStream instance for marshalling (objects -> xml) or unmarshalling (xml -> objects).
Internally XStream uses reflection, the readObject and readResolve methods of standard Java object serialization.
You get a good and speedy tutorial here:
To give a short overview of how it works, I also provide some sample code which marshalls and unmarshalls a data structure.
The marshalling / unmarshalling happens all in the main method, the rest is just code to generate some test objects and populate some data to them.
It is super simple to configure the xStream instance and marshalling / unmarshalling is done with one line of code each.
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
import com.thoughtworks.xstream.XStream;
public class XStreamIsGreat {
public static void main(String[] args) {
XStream xStream = new XStream();
xStream.alias("good", Good.class);
xStream.alias("pRoDuCeR", Producer.class);
xStream.alias("customer", Customer.class);
Producer a = new Producer("Apple");
Producer s = new Producer("Samsung");
Customer c = new Customer("Someone").add(new Good("S4", 10, new BigDecimal(600), s))
.add(new Good("S4 mini", 5, new BigDecimal(450), s)).add(new Good("I5S", 3, new BigDecimal(875), a));
String xml = xStream.toXML(c); // objects -> xml
System.out.println("Marshalled:\n" + xml);
Customer unmarshalledCustomer = (Customer)xStream.fromXML(xml); // xml -> objects
}
static class Good {
Producer producer;
String name;
int quantity;
BigDecimal price;
Good(String name, int quantity, BigDecimal price, Producer p) {
this.producer = p;
this.name = name;
this.quantity = quantity;
this.price = price;
}
}
static class Producer {
String name;
public Producer(String name) {
this.name = name;
}
}
static class Customer {
String name;
public Customer(String name) {
this.name = name;
}
List<Good> stock = new ArrayList<Good>();
Customer add(Good g) {
stock.add(g);
return this;
}
}
}

Ok, already having DOM, JaxB and XStream in the list of answers, there is still a complete different way to read and write XML: Data projection You can decouple the XML structure and the Java structure by using a library that provides read and writeable views to the XML Data as Java interfaces. From the tutorials:
Given some real world XML:
<weatherdata>
<weather
...
degreetype="F"
lat="50.5520210266113" lon="6.24060010910034"
searchlocation="Monschau, Stadt Aachen, NW, Germany"
... >
<current ... skytext="Clear" temperature="46"/>
</weather>
</weatherdata>
With data projection you can define a projection interface:
public interface WeatherData {
#XBRead("/weatherdata/weather/#searchlocation")
String getLocation();
#XBRead("/weatherdata/weather/current/#temperature")
int getTemperature();
#XBRead("/weatherdata/weather/#degreetype")
String getDegreeType();
#XBRead("/weatherdata/weather/current/#skytext")
String getSkytext();
/**
* This would be our "sub projection". A structure grouping two attribute
* values in one object.
*/
interface Coordinates {
#XBRead("#lon")
double getLongitude();
#XBRead("#lat")
double getLatitude();
}
#XBRead("/weatherdata/weather")
Coordinates getCoordinates();
}
And use instances of this interface just like POJOs:
private void printWeatherData(String location) throws IOException {
final String BaseURL = "http://weather.service.msn.com/find.aspx?outputview=search&weasearchstr=";
// We let the projector fetch the data for us
WeatherData weatherData = new XBProjector().io().url(BaseURL + location).read(WeatherData.class);
// Print some values
System.out.println("The weather in " + weatherData.getLocation() + ":");
System.out.println(weatherData.getSkytext());
System.out.println("Temperature: " + weatherData.getTemperature() + "°"
+ weatherData.getDegreeType());
// Access our sub projection
Coordinates coordinates = weatherData.getCoordinates();
System.out.println("The place is located at " + coordinates.getLatitude() + ","
+ coordinates.getLongitude());
}
This works even for creating XML, the XPath expressions can be writable.

SAX parser is working differently with a DOM parser, it neither load any XML document into memory nor create any object representation of the XML document. Instead, the SAX parser use callback function org.xml.sax.helpers.DefaultHandler to informs clients of the XML document structure.
SAX Parser is faster and uses less memory than DOM parser.
See following SAX callback methods :
startDocument() and endDocument() – Method called at the start and end of an XML document.
startElement() and endElement() – Method called at the start and end of a document element.
characters() – Method called with the text contents in between the start and end tags of an XML document element.
XML file
Create a simple XML file.
<?xml version="1.0"?>
<company>
<staff>
<firstname>yong</firstname>
<lastname>mook kim</lastname>
<nickname>mkyong</nickname>
<salary>100000</salary>
</staff>
<staff>
<firstname>low</firstname>
<lastname>yin fong</lastname>
<nickname>fong fong</nickname>
<salary>200000</salary>
</staff>
</company>
XML parser:
Java file Use SAX parser to parse the XML 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 ReadXMLFile {
public static void main(String argv[]) {
try {
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
DefaultHandler handler = new DefaultHandler() {
boolean bfname = false;
boolean blname = false;
boolean bnname = false;
boolean bsalary = false;
public void startElement(String uri, String localName,String qName,
Attributes attributes) throws SAXException {
System.out.println("Start Element :" + qName);
if (qName.equalsIgnoreCase("FIRSTNAME")) {
bfname = true;
}
if (qName.equalsIgnoreCase("LASTNAME")) {
blname = true;
}
if (qName.equalsIgnoreCase("NICKNAME")) {
bnname = true;
}
if (qName.equalsIgnoreCase("SALARY")) {
bsalary = true;
}
}
public void endElement(String uri, String localName,
String qName) throws SAXException {
System.out.println("End Element :" + qName);
}
public void characters(char ch[], int start, int length) throws SAXException {
if (bfname) {
System.out.println("First Name : " + new String(ch, start, length));
bfname = false;
}
if (blname) {
System.out.println("Last Name : " + new String(ch, start, length));
blname = false;
}
if (bnname) {
System.out.println("Nick Name : " + new String(ch, start, length));
bnname = false;
}
if (bsalary) {
System.out.println("Salary : " + new String(ch, start, length));
bsalary = false;
}
}
};
saxParser.parse("c:\\file.xml", handler);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Result
Start Element :company
Start Element :staff
Start Element :firstname
First Name : yong
End Element :firstname
Start Element :lastname
Last Name : mook kim
End Element :lastname
Start Element :nickname
Nick Name : mkyong
End Element :nickname
and so on...
Source(MyKong) - http://www.mkyong.com/java/how-to-read-xml-file-in-java-sax-parser/

How to read an online XML file for currency rates in java

I'm building a simple currency converter which needs to sue online rates. I found the following API from the European Central Bank to use:
http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml
My problem is im struggling to implement it. Here is what i have so far after using a bunch of different sources to try and get this code together.
try{
URL url = new URL("http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml");
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(new InputSource(url.openStream()));
doc.getDocumentElement().normalize();
NodeList nodeList1 = doc.getElementsByTagName("Cube");
for(int i = 0; i < nodeList1.getLength(); i++){
Node node = nodeList1.item(i);
}
}
catch(Exception e){
}
So what i thought is that this code would take down all the nodes which tart with "Cube", and contain the rates.
Anyone have an easier wya to pull down the rates from the API into an array in the order they appear on the XML as that's all I'm trying to do
Thanks

XPath is one way to answer this, since you just want to extract information from the XML and not change the XML. The structure of the XML suggests that you're looking for nodes that are Cube nodes, that are child of Cube which is also a child of Cube -- Cube nested three times, so extract nodes with an XPath compiled using this String: "//Cube/Cube/Cube". This looks for nodes that have Cube nested 3 times located anywhere (the //) in the Document:
XPathExpression expr = xpath.compile("//Cube/Cube/Cube");
Then check the nodes for a "currency" attribute. If they have this, then they also have a "rate" attribute, and then extract this information.
NamedNodeMap attribs = node.getAttributes();
if (attribs.getLength() > 0) {
Node currencyAttrib = attribs.getNamedItem(CURRENCY);
if (currencyAttrib != null) {
String currencyTxt = currencyAttrib.getNodeValue();
String rateTxt = attribs.getNamedItem(RATE).getNodeValue();
// ...
}
}
Where CURRENCY = "currency" and RATE = "rate"
For example:
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.*;
import javax.xml.xpath.*;
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class TestXPath {
private static final String CURRENCY = "currency";
private static final String CUBE_NODE = "//Cube/Cube/Cube";
private static final String RATE = "rate";
public static void main(String[] args) {
List<CurrencyRate> currRateList = new ArrayList<>();
DocumentBuilderFactory builderFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder builder = null;
try {
builder = builderFactory.newDocumentBuilder();
} catch (ParserConfigurationException e) {
e.printStackTrace();
}
Document document = null;
String spec = "http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml";
try {
URL url = new URL(spec);
InputStream is = url.openStream();
document = builder.parse(is);
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
String xPathString = CUBE_NODE;
XPathExpression expr = xpath.compile(xPathString);
NodeList nl = (NodeList) expr.evaluate(document, XPathConstants.NODESET);
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
NamedNodeMap attribs = node.getAttributes();
if (attribs.getLength() > 0) {
Node currencyAttrib = attribs.getNamedItem(CURRENCY);
if (currencyAttrib != null) {
String currencyTxt = currencyAttrib.getNodeValue();
String rateTxt = attribs.getNamedItem(RATE).getNodeValue();
currRateList.add(new CurrencyRate(currencyTxt, rateTxt));
}
}
}
} catch (SAXException | IOException | XPathExpressionException e) {
e.printStackTrace();
}
for (CurrencyRate currencyRate : currRateList) {
System.out.println(currencyRate);
}
}
}
public class CurrencyRate {
private String currency;
private String rate; // ?double
public CurrencyRate(String currency, String rate) {
super();
this.currency = currency;
this.rate = rate;
}
public String getCurrency() {
return currency;
}
public String getRate() {
return rate;
}
#Override
public String toString() {
return "CurrencyRate [currency=" + currency + ", rate=" + rate + "]";
}
// equals, hashCode,....
}

Java - XLSX parse & database export

I have an excel that filled about 50k-60k rows.
I have to make that excel content uploaded into MySQL, usually I use the apache poi to read and upload it into MySQL, but this file cannot be read using apache poi cause the file was to LARGE.
Can anybody guide me how to do that? Here is my sample code to upload the content into MySQL using apache poi (it works for some little xlsx files that contains 1000-2000 rows)
public static void uploadCrossSellCorpCard(FileItem file, String dbtable) {
System.out.println("UploadUtil Running" + file.getFileName().toString());
try {
for(int i = 0; i<=sheetx.getLastRowNum(); i++){
row = sheetx.getRow(i);
try{
int oc = (int) row.getCell(0).getNumericCellValue();
if((String.valueOf(oc).matches("[A-Za-z0-9]{3}"))){
String rm_name = row.getCell(1).getStringCellValue();
String company = row.getCell(2).getStringCellValue();
String product = row.getCell(3).getStringCellValue();
String detail = row.getCell(4).getStringCellValue();
String type = row.getCell(5).getStringCellValue();
String sql = "INSERT INTO " + dbtable + " VALUES('"
+ oc + "','" + rm_name + "','" + company + "','"
+ product + "','" + detail + "','" + type + "')";
save(sql);
System.out.println("Import rows " + i);
}
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (NullPointerException e) {
System.out.println(e);
}
}
System.out.println("Success import xlsx to mysql table");
} catch (NullPointerException e){
System.out.println(e);
System.out.println("Select the file first before uploading");
}
}
Note: I use hibernate method for handle upload schema.. "save(sql)" is calling my hibernate method

You can try using Apache POI SAX - read the section --> XSSF and SAX (Event API) on https://poi.apache.org/spreadsheet/how-to.html
You can read entire excel with 60k rows or even 100k rows just like reading an xml file. only thing you need to take care is empty cell since xml tag for empty cell will just skip the cell it but you may like to update null value in db table for the cell representing empty value.
Solution --> you can read each row and fire insert statement in a loop. and keep watch on empty cell by monitoring cell address if gap occurs then check respective column name and accordingly update your insert statement with null value.
I hope this helps you. below sample code read excel and store it in ArrayList of ArrayList for tabular representation. I am printing message in console - "new row begins" before start reading and printing row. and cell number of each value before printing cell value itself.
I have not taken care of cell gaps for empty cell but that you can code it based on finding cell gap since in my case I don't have empty cell.
look for cell address in the console that helps you in spotting any gap and handling it as you wish.
Run this code and works fine for me. don't forget to add xmlbeans-2.3.0.jar
other then jars required by import statements.
import java.io.InputStream;
import java.util.ArrayList;
import org.apache.commons.lang3.time.DurationFormatUtils;
import org.apache.commons.lang3.time.StopWatch;
import org.apache.poi.xssf.eventusermodel.XSSFReader;
import org.apache.poi.xssf.model.SharedStringsTable;
import org.apache.poi.xssf.usermodel.XSSFRichTextString;
import org.apache.poi.openxml4j.opc.OPCPackage;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.helpers.XMLReaderFactory;
public class ExcelToStringArray implements Cloneable {
public static ArrayList<ArrayList<StringBuilder>> stringArrayToReturn = new ArrayList<ArrayList<StringBuilder>>();
public static ArrayList<StringBuilder> retainedString;
public static Integer lineCounter = 0;
public ArrayList<ArrayList<StringBuilder>> GetSheetInStringArray(String PathtoFilename, String rId)
throws Exception {
ExcelToStringArray myParser = new ExcelToStringArray();
myParser.processOneSheet(PathtoFilename, rId);
return stringArrayToReturn;
}
public void processOneSheet(String PathtoFilename, String rId) throws Exception {
OPCPackage pkg = OPCPackage.open(PathtoFilename);
XSSFReader r = new XSSFReader(pkg);
SharedStringsTable sst = r.getSharedStringsTable();
XMLReader parser = fetchSheetParser(sst);
InputStream sheet = r.getSheet(rId);
InputSource sheetSource = new InputSource(sheet);
parser.parse(sheetSource);
sheet.close();
}
public XMLReader fetchSheetParser(SharedStringsTable sst) throws SAXException {
XMLReader parser = XMLReaderFactory.createXMLReader("org.apache.xerces.parsers.SAXParser");
ContentHandler handler = new SheetHandler(sst);
parser.setContentHandler(handler);
return parser;
}
private class SheetHandler extends DefaultHandler {
private SharedStringsTable sst;
private String lastContents;
private boolean nextIsString;
private SheetHandler(SharedStringsTable sst) {
this.sst = sst;
}
public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException {
if (name.equals("row")) {
retainedString = new ArrayList<StringBuilder>();
if (retainedString.isEmpty()) {
stringArrayToReturn.add(retainedString);
retainedString.clear();
}
System.out.println("New row begins");
retainedString.add(new StringBuilder(lineCounter.toString()));
lineCounter++;
}
// c => cell
if (name.equals("c")) {
// Print the cell reference
System.out.print(attributes.getValue("r") + " - ");
// System.out.print(attributes.getValue("r") + " - ");
// Figure out if the value is an index in the SST
String cellType = attributes.getValue("t");
if (cellType != null && cellType.equals("s")) {
nextIsString = true;
} else {
nextIsString = false;
}
}
// Clear contents cache
lastContents = "";
}
public void endElement(String uri, String localName, String name) throws SAXException {
// Process the last contents as required.
// Do now, as characters() may be called more than once
if (nextIsString) {
int idx = Integer.parseInt(lastContents);
lastContents = new XSSFRichTextString(sst.getEntryAt(idx)).toString();
nextIsString = false;
}
// v => contents of a cell
// Output after we've seen the string contents
if (name.equals("v")) {
System.out.println(lastContents);
// value of cell what it string or number
retainedString.add(new StringBuilder(lastContents));
}
}
public void characters(char[] ch, int start, int length) throws SAXException {
lastContents += new String(ch, start, length);
}
}
public static void main(String[] args) throws Exception {
StopWatch watch = new StopWatch();
watch.start();
ExcelToStringArray generate = new ExcelToStringArray();
// rID1 is first sheet in my workbook for rId2 for second sheet and so
// on.
generate.GetSheetInStringArray("D:\\Users\\NIA\\Desktop\\0000_MasterTestSuite.xlsx", "rId10");
watch.stop();
System.out.println(DurationFormatUtils.formatDurationWords(watch.getTime(), true, true));
System.out.println("done");
System.out.println(generate.stringArrayToReturn);
}
}

Creating a XML parser for Java

I'm making a Java application that displays X3D models and I'm creating an XML parser for it. The Java code that I have for it is
package domparserexample.java;
import java.io.IOException;
import java.util.Iterator;
import javax.lang.model.element.Element;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class DomParserExampleJava {
private void parseXmlFile() throws IOException, ParserConfigurationException{
//get the factory
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
//Using factory get an instance of document builder
DocumentBuilder db = dbf.newDocumentBuilder();
//parse using builder to get DOM representation of the XML file
Document dom = db.parse("employees.xml");
}catch(SAXException se) {
se.printStackTrace();
}catch(IOException ioe) {
ioe.printStackTrace();
}
}
private void parseDocument(){
//get the root element
Element docEle = dom.getDocumentElement();
//get a nodelist of elements
NodeList nl = docEle.getElementsByTagName("Employee");
if(nl != null && nl.getLength() > 0) {
for(int i = 0 ; i < nl.getLength();i++) {
//get the employee element
Element el = (Element)nl.item(i);
//get the Employee object
Employee e = getEmployee(el);
//add it to list
myEmpls.add(e);
}
}
}
/**
* I take an employee element and read the values in, create
* an Employee object and return it
*/
private Employee getEmployee(Element empEl) {
//for each <employee> element get text or int values of
//name ,id, age and name
String name = getTextValue(empEl,"Name");
int id = getIntValue(empEl,"Id");
int age = getIntValue(empEl,"Age");
String type = empEl.getAttribute("type");
//Create a new Employee with the value read from the xml nodes
Employee e = new Employee(name,id,age,type);
return e;
}
private String getTextValue(Element ele, String tagName) {
String textVal = null;
NodeList nl = ele.getElementsByTagName(tagName);
if(nl != null && nl.getLength() > 0) {
Element el = (Element)nl.item(0);
textVal = el.getFirstChild().getNodeValue();
}
return textVal;
}
private int getIntValue(Element ele, String tagName) {
//in production application you would catch the exception
return Integer.parseInt(getTextValue(ele,tagName));
}
private void printData(){
System.out.println("No of Employees '" + myEmpls.size() + "'.");
Iterator it = myEmpls.iterator();
while(it.hasNext()) {
System.out.println(it.next().toString());
}
}
}
And the XML code is:
<?xml version="1.0" encoding="UTF-8"?>
<Personnel>
<Employee type="permanent">
<Name>Seagull</Name>
<Id>3674</Id>
<Age>34</Age>
</Employee>
<Employee type="contract">
<Name>Robin</Name>
<Id>3675</Id>
<Age>25</Age>
</Employee>
<Employee type="permanent">
<Name>Crow</Name>
<Id>3676</Id>
<Age>28</Age>
</Employee>
</Personnel>
However, I'm getting some errors on lines 49, 76, 93, and 96 in the DomParserExample.java file and I don't know why it's happening. All the errors say that they cannot find symbol and symbol: method getElemantsByTagName(String), symbol: method getAttribute(String), symbol: method getElementByTagName(String), and symbol: method getFirstChild().

For me it is working with the following code. I made some changes to your code.
DomParserExampleJava.java
package domparserexample.java;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
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.NodeList;
import org.xml.sax.SAXException;
public class DomParserExampleJava {
private List<Employee> myEmpls = new ArrayList<Employee>();
public static void main(String[] args) throws IOException, ParserConfigurationException {
DomParserExampleJava domParser = new DomParserExampleJava();
domParser.parseXmlFile();
}
private void parseXmlFile() throws IOException, ParserConfigurationException {
// get the factory
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
// Using factory get an instance of document builder
DocumentBuilder db = dbf.newDocumentBuilder();
// parse using builder to get DOM representation of the XML file
Document dom = db.parse("employees.xml");
parseDocument(dom);
printData();
} catch (SAXException se) {
se.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
private void parseDocument(Document dom) {
// get the root element
Element docEle = dom.getDocumentElement();
// get a nodelist of elements
NodeList nl = docEle.getElementsByTagName("Employee");
if (nl != null && nl.getLength() > 0) {
for (int i = 0; i < nl.getLength(); i++) {
// get the employee element
Element el = (Element) nl.item(i);
// get the Employee object
Employee e = getEmployee(el);
// add it to list
myEmpls.add(e);
}
}
}
/**
* I take an employee element and read the values in, create an Employee object and return it
*/
private Employee getEmployee(Element empEl) {
// for each <employee> element get text or int values of
// name ,id, age and name
String name = getTextValue(empEl, "Name");
int id = getIntValue(empEl, "Id");
int age = getIntValue(empEl, "Age");
String type = empEl.getAttribute("type");
// Create a new Employee with the value read from the xml nodes
Employee e = new Employee(name, id, age, type);
return e;
}
private String getTextValue(Element ele, String tagName) {
String textVal = null;
NodeList nl = ele.getElementsByTagName(tagName);
if (nl != null && nl.getLength() > 0) {
Element el = (Element) nl.item(0);
textVal = el.getFirstChild().getNodeValue();
}
return textVal;
}
private int getIntValue(Element ele, String tagName) {
// in production application you would catch the exception
return Integer.parseInt(getTextValue(ele, tagName));
}
private void printData() {
System.out.println("No of Employees '" + myEmpls.size() + "'.");
Iterator<Employee> it = myEmpls.iterator();
while (it.hasNext()) {
System.out.println(it.next().toString());
}
}
}
Employee.java
package domparserexample.java;
public class Employee {
private String name;
private int id;
private int age;
private String type;
public Employee(String name, int id, int age, String type) {
this.name = name;
this.id = id;
this.age = age;
this.type = type;
}
public String toString() {
return id + ": " + name + ", age: " + age + ", type: " + type;
}
}
employees.xml
In your example <?xml version="1.0" encoding="UTF-8"?> appears a second time in the middle of the XML document. This lead to an error.
<?xml version="1.0" encoding="UTF-8"?>
<Personnel>
<Employee type="permanent">
<Name>Seagull</Name>
<Id>3674</Id>
<Age>34</Age>
</Employee>
<Employee type="contract">
<Name>Robin</Name>
<Id>3675</Id>
<Age>25</Age>
</Employee>
<Employee type="permanent">
<Name>Crow</Name>
<Id>3676</Id>
<Age>28</Age>
</Employee>
</Personnel>
If I execute the Java file it returns:
No of Employees '3'.
3674: Seagull, age: 34, type: permanent
3675: Robin, age: 25, type: contract
3676: Crow, age: 28, type: permanent

You are using the wrong ELementclass:
import javax.lang.model.element.Element;
is wrong, use:
import org.w3c.dom.Element;
That should work.

Returning XML from query result in servlet

I'm trying to return an XML file based on my query results. I'm very new to this so I'm not really sure where I'm going wrong. Is this a realistic way to go about doing this or is there something simpler? Right now I'm getting these exceptions:
Error performing query: javax.servlet.ServletException: org.xml.sax.SAXParseException: Content is not allowed in prolog.
If I run my query in isql*plus, it does execute
import java.io.*;
import java.util.*;
import java.sql.*; // JDBC packages
import javax.servlet.*;
import javax.servlet.http.*;
import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
public class step5 extends HttpServlet {
public static final String DRIVER = "sun.jdbc.odbc.JdbcOdbcDriver";
public static final String URL = "jdbc:odbc:rreOracle";
public static final String username = "cm485a10";
public static final String password = "y4e8f7s5";
SAXParserFactory factory;
public void init() throws ServletException {
factory = SAXParserFactory.newInstance();
}
public void doGet (HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException
{
PrintWriter out = response.getWriter();
Connection con = null;
try {
Class.forName(DRIVER);
con = DriverManager.getConnection(URL,username,password);
try {
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("SELECT sale_id, home_id, agent_id, customer_id FROM sale");
String xml = "";
xml = xml + "<sales_description>";
xml = xml + "<sale>";
boolean courseDataDone = false;
while (rs.next()) {
String sale_id = rs.getString(1);
String home_id = rs.getString(2);
String agent_id = rs.getString(3);
String customer_id = rs.getString(4);
if (!courseDataDone) {
xml = xml + "<sale_id>" + sale_id + "</sale_id>" +
"<home_id>" + home_id + "</home_id>" +
"<agent_id>" + agent_id + "</agent_id>" +
"<customer_id>" + customer_id + "</customer_id>" +
"" +
"";
courseDataDone = true;
}
}
xml = xml + "</sale>" +
"</sales_description>";
try {
SAXParser parser = factory.newSAXParser();
InputSource input = new InputSource(new StringReader(xml));
parser.parse(input, new DefaultHandler());
} catch (ParserConfigurationException e) {
throw new ServletException(e);
} catch (SAXException e) {
throw new ServletException(e);
}
response.setContentType("text/xml;charset=UTF-8");
out.write(xml);
} catch(Exception ex) {
out.println("Error performing query: " + ex);
con.close();
return;
}
} catch(Exception ex) {
out.println("Error performing DB connection: " + ex);
return;
}
}
}
Any help/tips would be appreciated.

You're missing the prolog. Add this to beginning of your XML:
<?xml version="1.0" encoding="UTF-8"?>
By the way, you don't need the SAX parser here. You aren't modifying the XML at all. Get rid of the parser and just write xml directly to the response. You are also not handling JDBC resources correctly in try-with-resources. Here's a basic example of the improvement:
response.setContentType("text/xml;charset=UTF-8");
PrintWriter writer = response.getWriter();
writer.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
writer.append("<sales_description>");
try (
Connection connection = dataSource.getConnection();
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("SELECT sale_id, home_id, agent_id, customer_id FROM sale");
) {
if (resultSet.next()) {
writer.append("<sale>");
writer.append("<sale_id>").append(resultSet.getString("sale_id")).append("</sale_id>");
writer.append("<home_id>").append(resultSet.getString("home_id")).append("</home_id>");
writer.append("<agent_id>").append(resultSet.getString("agent_id")).append("</agent_id>");
writer.append("</sale>");
}
} catch (SQLException e) {
throw new ServletException(e);
}
writer.append("</sales_description>");
To write all records, just replace if (resultSet.next()) by while (resultSet.next()).
To handle the exception more gracefully, i.e. throwing an ServletException which ends in an error page instead of a halfbaked XML, you'd like to build the XML using StringBuilder. Just replace PrintWriter by new StringBuilder() and then at end, do response.getWriter().write(builder.toString()).

One tip would be layering your code a bit more. Servlets shouldn't be importing from java.sql. Put that code in a separate class, test it, and let your servlet call its methods.
You're creating XML in the most brain dead way possible by concatentating strings that way. Why not use a library like JDOM or at least a StringBuilder?
And skaffman's right: your code makes no sense otherwise.
Here are a few ideas you can think about for layering. Start with a model object for Sale - after all, Java's an object-oriented language:
package badservlet.model;
public class Sale
{
private String saleId;
private String homeId;
private String agentId;
private String customerId;
public Sale(String saleId, String homeId, String agentId, String customerId)
{
if ((saleId == null) || (saleId.trim().length() == 0)
throw new IllegalArgumentException("sales id cannot be blank or null");
if ((homeId == null) || (homeId.trim().length() == 0)
throw new IllegalArgumentException("home id cannot be blank or null");
if ((agentId == null) || (agentId.trim().length() == 0)
throw new IllegalArgumentException("agent id cannot be blank or null");
if ((customerId == null) || (customerId.trim().length() == 0)
throw new IllegalArgumentException("customer id cannot be blank or null");
this.saleId = saleId;
this.homeId = homeId;
this.agentId = agentId;
this.customerId = customerId;
}
public String getSaleId()
{
return saleId;
}
public String getHomeId()
{
return homeId;
}
public String getAgentId()
{
return agentId;
}
public String getCustomerId()
{
return customerId;
}
#Override
public String toString()
{
return "Sale{" +
"saleId='" + saleId + '\'' +
", homeId='" + homeId + '\'' +
", agentId='" + agentId + '\'' +
", customerId='" + customerId + '\'' +
'}';
}
}
For persistence, start with a DAO interface:
package badservlet.persistence;
import badservlet.model.Sale;
import java.sql.SQLException;
import java.util.List;
public interface SaleDao
{
List<Sale> find() throws SQLException;
}
And its implementation:
package badservlet.persistence;
import badservlet.model.Sale;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
public class SaleDaoImpl implements SaleDao
{
private static final String SELECT_ALL_SQL = "SELECT sale_id, home_id, agent_id, customer_id FROM sale";
private Connection connection;
public SaleDaoImpl(Connection connection)
{
this.connection = connection;
}
public SaleDaoImpl(DataSource dataSource) throws SQLException
{
this(dataSource.getConnection());
}
public List<Sale> find() throws SQLException
{
List<Sale> allSales = new ArrayList<Sale>();
Statement st = null;
ResultSet rs = null;
try
{
st = this.connection.createStatement();
rs = st.executeQuery(SELECT_ALL_SQL);
while (rs.next())
{
String saleId = rs.getString("sale_id");
String homeId = rs.getString("home_id");
String agentId = rs.getString("agent_id");
String customerId = rs.getString("customer_id");
Sale sale = new Sale(saleId, homeId, agentId, customerId);
allSales.add(sale);
}
}
catch (SQLException e)
{
e.printStackTrace();
}
finally
{
try { if (rs != null) rs.close(); } catch (SQLException e) { e.printStackTrace(); }
try { if (st != null) st.close(); } catch (SQLException e) { e.printStackTrace(); }
}
return allSales;
}
}
And an object-to-XML unmarshaller:
package badservlet.xml;
import badservlet.model.Sale;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.transform.JDOMResult;
import javax.xml.bind.JAXBException;
import javax.xml.transform.Result;
import java.util.List;
public class SaleUnmarshaller
{
public void unmarshal(Object object, Result xml) throws JAXBException
{
List<Sale> allSales = (List<Sale>) object;
Document document = new Document(new Element("sales"));
for (Sale sale : allSales)
{
Element child = new Element("sale");
child.setAttribute("id", sale.getSaleId());
child.addContent(new Element("home", sale.getHomeId()));
child.addContent(new Element("agent", sale.getAgentId()));
child.addContent(new Element("customer", sale.getCustomerId()));
document.addContent(child);
}
JDOMResult result = new JDOMResult();
result.setDocument(document);
xml = result;
}
}
Let your servlet instantiate these objects and call their methods.
It might look more complicated - more classes than just one - but you've accomplished two things: you've broken your problem down into smaller pieces, and you can test them separately.

What are you trying to accomplish here? This code looks very confusing for several reasons:
You're presumably trying to build up an XML string, but you're not appending any XML tags to it at all.
There's a lot of no-ops in there, such as xml = xml + ""; which doesn't achieve anything.
I'm not 100% sure what you want to achieve in the try block near the end. This block will have the side-effect of ensuring your xml string is valid XML, but if this is what you want to do there are probably clearer (and more efficient) ways of validating. If you're hoping it will magically transform your String into XML, then it won't (in fact no matter what, it can't modify the contents of the xml variable so this would be a no-op.
Perhaps it would help if you talked through what you're trying to do here, with particular reference to what you expect the state of affairs to be at each stage. Right now, you're building up a string that looks something like:
FirstSaleIDFirstHomeFirstAgentFirstCustomerSecondSaleIDSecondHomeSecondAgentSecondCustomer...
Then you try to parse this as XML. As you might expect, this is not valid XML hence the parser throws the error (in particular "no content in prolog" means that you have character data before the first tag definition).
I would give you advice on how to improve this but I really have no idea what you expect this to do...

Rather than using String concatanation for building XML, Trying using XML API's like DOM, JDOM etc.
Few Tutorial links:
http://www.w3schools.com/dom/default.asp
http://www.xul.fr/en/dom/
http://swik.net/JDOM+Tutorial
http://www.ibm.com/developerworks/java/library/j-jdom/

If we assume that this values you retrive form database
|sale_id | home_id | agent_id | customer_id |
| 1 | 10 | 100 | 1000 |
| 2 | 20 | 200 | 2000 |
| 3 | 30 | 300 | 3000 |
the xml a the end look like this
1010100100020003000
And after all You are tying to create a XML file from this.
What You should read about:
First about the ResultSet, i really doubt that those id are string not numbers.
next the class StringBuilder, the way you concat strings is wrong because strings is inmutable.
And for sure you should look about the Java API for XML