I have a string input from which I need to extract simple information, here is the sample xml (from mkyong):
<?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>
How I parse it within my code (I have a field String name in my class) :
public String getNameFromXml(String xml) {
try {
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
DefaultHandler handler = new DefaultHandler() {
boolean firstName = false;
public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
if (qName.equalsIgnoreCase("firstname")) {
firstName = true;
}
}
public void characters(char ch[], int start, int length) throws SAXException {
if (firstName) {
name = new String(ch, start, length);
System.out.println("First name is : " + name);
firstName = false;
}
}
};
saxParser.parse(xml.toString(), handler);
} catch (Exception e) {
e.printStackTrace();
}
return name;
}
I'm getting a java.io.FileNotFoundException and I see that it's trying to find a file myprojectpath + the entireStringXML
What am I doing wrong?
Addon :
Here is my main method :
public static void main(String[] args) {
Text tst = new Text("<?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>");
NameFilter cc = new NameFilter();
String result = cc.getNameFromXml(tst);
System.out.println(result);
}
You should replace the line saxParser.parse(xml.toString(), handler); with the following one:
saxParser.parse(new InputSource(new StringReader(xml)), handler);
I'm going to highlight another issue, which you're likely to hit once you read your file correctly.
The method
public void characters(char ch[], int start, int length)
won't always give you the complete text element. It's at liberty to give you the text element (content) 'n' characters at a time. From the doc:
SAX parsers may return all contiguous character data in a single
chunk, or they may split it into several chunks
So you should build up your text element string from each call to this method (e.g. using a StringBuilder) and only interpret/store that text once the corresponding endElement() method is called.
This may not impact you now. But it'll arise at some time in the future - likely when you least expect it. I've encountered it when moving from small to large XML documents, where buffering has been able to hold the whole small document, but not the larger one.
An example (in pseudo-code):
public void startElement() {
builder.clear();
}
public void characters(char ch[], int start, int length) {
builder.append(new String(ch, start, length));
}
public void endElement() {
// no do something with the collated text
builder.toString();
}
Mybe this help. it's uses javax.xml.parsers.DocumentBuilder, which is easier than SAX
public Document getDomElement(String xml){
Document doc = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource();
is.setCharacterStream(new StringReader(xml));
doc = db.parse(is);
} catch (ParserConfigurationException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (SAXException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (IOException e) {
Log.e("Error: ", e.getMessage());
return null;
}
// return DOM
return doc;
}
you can loop through the document by using NodeList and check each Node by it's name
You call parse with a String as the first parameter. According to the docu that string is interpreted as the URI to your file.
If you want to parse your String directly, you have to transform it to an InputStream in the first place for usage with the parse(InputSource is, DefaultHandler dh) method (docu):
// transform from string to inputstream
ByteArrayInputStream in = new ByteArrayInputStream(xml.toString().getBytes());
InputSource is = new InputSource();
is.setByteStream(in);
// start parsing
saxParser.parse(xml.toString(), handler);
Seems you took this example from here . You need to pass a file with absolute path an not a string to method SAXParser.parse(); Look the example closely. The method parse() defined as follows
public void parse(File f,
DefaultHandler dh)
throws SAXException,
IOException
If you want to parse a string anyways. There is another method which takes Inputstream.
public void parse(InputStream is,
DefaultHandler dh)
throws SAXException,
IOException
Then you need to convert your string to an InputStream. Here is how to do it.
Related
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/
I'm parsing a document that I cannot change from the internet using a SAX Parser. It was working just fine when the documents came formatted as such:
<outtertag>
<innertag>data</innertag>
<innerag>moreData</innertag>
</outtertag>
However, there are certain calls I make where the XML comes formatted without the outer tags, so I essentially get just a list of data, like such:
<innertag>data</innertag>
<innerag>moreData</innertag>
This seems silly to me, but I don't get to choose how the XML is formatted and it can't be changed for now. The problem is that it seems that the SAX Parser hits the endDocument event as soon as it hits the first closing innertag.
I have a rather hacky solution of converting the InputStream into a String, throwing tags around it, and then converting it back to an InputStream. It actually parses fine that way. But, surely there's a better way. I'd also would prefer not to write a whole other parser. Most of the tags are the same aside from the lack of opening and closing tags.
Just for the heck of it, I'll post the code, but it's pretty standard SAX Parser. The original is actually parsing about 30 some tags:
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
XMLReader xmlReader = saxParser.getXMLReader();
MyHandler handler = new MyHandler();
xmlReader.setContentHandler(handler);
InputSource inputSource = new InputSource(url.openStream());
xmlReader.parse(inputSource);
}
catch (SAXException e) { e.printStackTrace(); }
catch (ParserConfigurationException e) { e.printStackTrace(); }
catch(Exception e) { e.printStackTrace(); }
}
private class MyHandler extends DefaultHandler {
private StringBuilder content;
public MyHandler() {
content = new StringBuilder();
}
public void startElement(String uri, String localName, String qName,
Attributes atts) throws SAXException {
content = new StringBuilder();
if(localName.equalsIgnoreCase("innertag")) {
//Doing stuff
}
}
public void endElement(String uri, String localName, String qName)
throws SAXException {
//Doing stuff
}
public void characters(char[] ch, int start, int length)
throws SAXException {
content.append(ch, start, length);
}
public void endDocument() throws SAXException {
//When parsing the second type of document, hits this event almost immediately after parsing first tag
}
}
And, if it matters, here's my hacky code I'm using, but just feels wrong, yet it works:
BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
StringBuilder sb = new StringBuilder("<tag>");
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line);
}
sb.append("</tag>");
String xml =sb.toString();
InputStream is = new ByteArrayInputStream(xml.getBytes());
InputSource source = new InputSource(is);
xmlReader.parse(source);
I'd say what you're doing now is about as good as you'll get. The one thing to consider improving is the stream -> string -> stream conversion, especially if the documents are large. You could use something like Guava's ByteStreams.join(), which lets you concatenate streams together instead of strings. Something like the following:
import com.google.common.io.*;
import java.io.*;
public class ConcatenateStreams {
public static void main(String[] args) throws Exception {
InputStream malformedXmlContent = externalXmlStream();
InputSupplier<InputStream> joined = ByteStreams.join(
inputSupplier("<root>"),
inputSupplier(malformedXmlContent),
inputSupplier("</root>"));
ByteStreams.copy(joined, System.out);
}
private static InputStream externalXmlStream() {
return new ByteArrayInputStream("<foo>5</foo><bar>10</bar>".getBytes());
}
private static InputSupplier<InputStream> inputSupplier(final String text) {
return inputSupplier(new ByteArrayInputStream(text.getBytes()));
}
private static InputSupplier<InputStream> inputSupplier(final InputStream inputStream) {
return new InputSupplier<InputStream>() {
#Override
public InputStream getInput() throws IOException {
return inputStream;
}
};
}
}
which outputs:
<root><foo>5</foo><bar>10</bar></root>
The XML you have is not a well-formed document, but it is a well-formed external parsed entity, which means it can be referenced from a well-formed document by means of an entity reference. So create a skeleton document like this:
<!DOCTYPE doc [
<!ENTITY e SYSTEM "data.xml">
]>
<doc>&e;</doc>
where data.xml is your XML, and pass this document to the XML parser in place of the original. Beats writing dozens of lines of Java code.
I am trying to fetch data from a xml file in java using sax parser. I successfully got small amount of data but when data becomes too large and in multiple lines it gives only two lines of data, not all the lines. I am trying following code-
InputStreamReader isr = new InputStreamReader(is);
InputSource source = new InputSource(isr);
SAXParserFactory factory = SAXParserFactory.newInstance();
factory.setNamespaceAware(true);
SAXParser parser = factory.newSAXParser();
XMLReader xr = parser.getXMLReader();
GeofenceParametersXMLHandler handler = new GeofenceParametersXMLHandler();
xr.setContentHandler(handler);
xr.parse(source);
And my GeofenceParametersXMLHandler is-
private boolean inTimeZone = false;
private boolean inCoordinate = false;
private boolean outerBoundaryIs = false;
private boolean innerBoundaryIs = false;
private String timeZone;
private List<String> innerCoordinates = new ArrayList<String>();
private String outerCoordinates;
public String getTimeZone() {
return timeZone;
}
public List<String> getInnerCoordinates() {
return innerCoordinates;
}
public String getOuterCoordinates() {
return outerCoordinates;
}
#Override
public void characters(char[] ch, int start, int length) throws SAXException {
super.characters(ch, start, length);
if (this.inTimeZone) {
this.timeZone = new String(ch, start, length);
this.inTimeZone = false;
}
if (this.inCoordinate && this.innerBoundaryIs) {
this.innerCoordinates.add(new String(ch, start, length));
this.inCoordinate = false;
this.innerBoundaryIs = false;
}
if (this.inCoordinate && this.outerBoundaryIs) {
this.outerCoordinates = new String(ch, start, length);
this.inCoordinate = false;
this.outerBoundaryIs = false;
}
}
#Override
public void endElement(String uri, String localName, String name) throws SAXException {
super.endElement(uri, localName, name);
}
#Override
public void startDocument() throws SAXException {
super.startDocument();
}
#Override
public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException {
super.startElement(uri, localName, name, attributes);
if (localName.equalsIgnoreCase("timezone")) {
this.inTimeZone = true;
}
if (localName.equalsIgnoreCase("outerBoundaryIs")) {
this.outerBoundaryIs = true;
}
if (localName.equalsIgnoreCase("innerBoundaryIs")) {
this.innerBoundaryIs = true;
}
if (localName.equalsIgnoreCase("coordinates")) {
this.inCoordinate = true;
}
}
And the xml file is-
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2"
xmlns:gx="http://www.google.com/kml/ext/2.2">
<Placemark>
<name>gx:altitudeMode Example</name>
<timezone>EASTERN</timezone>
<Polygon>
<extrude>1</extrude>
<altitudeMode>relativeToGround</altitudeMode>
<outerBoundaryIs>
<LinearRing>
<coordinates>
-77.05788457660967,38.87253259892824,100
-77.05465973756702,38.87291016281703,100
-77.05315536854791,38.87053267794386,100
-77.05552622493516,38.868757801256,100
-77.05844056290393,38.86996206506943,100
-77.05788457660967,38.87253259892824,100
</coordinates>
</LinearRing>
</outerBoundaryIs>
</Polygon>
I always got two line of data for coordinates. But when they are in single line I got complete data. How to fetch complete data in multiple line?
Thanks in Advance.
The characters() method won't necessarily give you all the text data in one go (this is a very common misconception, btw).
The proper approach is to concatenate all the data returned by successive calls to characters() (using a StringBuilder or similar). Once your endElement() method is called, you can then treat that text buffer as complete and process it as such.
From the doc:
The Parser will call this method to report each chunk of character
data. SAX parsers may return all contiguous character data in a single
chunk, or they may split it into several chunks
Often you see that for a small XML doc one call to characters() will suffice. However as your XML doc increases in size, you'll find that due to buffering etc. you'll start getting multiple calls. Consequently each call treated on its own appears to be incomplete.
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/
I am using the SAX Parser for XML Parsing. The problem is for the following XML code:
<description>
Designer:Paul Smith Color:Plain Black Fabric/Composition:100% cotton Weave/Pattern:pinpoint Sleeve:Long-sleeved Fit:Classic Front style:Placket front Back style:Side pleat back Collar:Classic/straight collar Button:Pearlescent front button Pocket:rounded chest pocket Hem:Rounded hem
</description>
I get this:
Designer:Paul Smith
Color:Plain Black
The other parts are missing. The same thing happens for a few other lines. Can anyone kindly tell me whats the problem with my approach ?
My code is given below:
Parser code:
try {
/** Handling XML */
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();
XMLReader xr = sp.getXMLReader();
/** Send URL to parse XML Tags */
URL sourceUrl = new URL(
"http://50.19.125.224/Demo/VeryGoodSex_and_the_City_S6E6.xml");
/** Create handler to handle XML Tags ( extends DefaultHandler ) */
MyXMLHandler myXMLHandler = new MyXMLHandler();
xr.setContentHandler((ContentHandler) myXMLHandler);
xr.parse(new InputSource(sourceUrl.openStream()));
} catch (Exception e) {
System.out.println("XML Pasing Excpetion = " + e);
}
Object to hold XML parsed Info:
public class ParserObject {
String name=null;
String description=null;
String bitly=null; //single
String productLink=null;//single
String productPrice=null;//single
Vector<String> price=new Vector<String>();
}
Handler class:
public void endElement(String uri, String localName, String qName)
throws SAXException {
currentElement = false;
if (qName.equalsIgnoreCase("title"))
{
xmlDataObject[index].name=currentValue;
}
else if (qName.equalsIgnoreCase("artist"))
{
xmlDataObject[index].artist=currentValue;
}
}
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
currentElement = true;
if (qName.equalsIgnoreCase("allinfo"))
{
System.out.println("started");
}
else if (qName.equalsIgnoreCase("tags"))
{
insideTag=1;
}
}
public void characters(char[] ch, int start, int length)
throws SAXException {
if (currentElement) {
currentValue = new String(ch, start, length);
currentElement = false;
}
}
You have to concatenate characters which the parser gives to you until it calls endElement.
Try removing currentElement = false; from characters handler, and
currentValue = currentValue + new String(ch, start, length);
Initialize currentValue with an empty string or handle null value in the expression above.
I think characters read some, but not all characters at the same time.
Thus, you only get the first "chunk".
Try printing each character chunk on a separate line, as debugging (before the if).