Using XML to transport information between different systems is nowadays a state of the art technology. Searching the WEB you'll find a huge set of examples how to validate and parse an XML document. But when it comes to the point where you have to create a XML document and send it as stream (i.g. character-stream, string, byte-array, etc.) to another system, it becomes difficult to find a proper example. Furthermore, different implementations of the DOM specification using different class names to do the same thing.
Here comes an example which creates a XML Document using DOM and transforms it to a String. We used the XERCES Java Parser V1_4_3 from apache.org.
Xerces (named after the Xerces Blue butterfly) provides world-class XML parsing and generation. Fully-validating parsers are available for both Java and C++, implementing the W3C XML and DOM (Level 1 and 2) standards, as well as the de facto SAX (version 2) standard. The parsers are highly modular and configurable. Initial support for XML Schema (draft W3C standard) is also provided.
<?xml version="1.0" encoding="UTF-8"?>
<ProbeMsg>
<TimeStamp>2001-11-30T09:08:07Z</TimeStamp>
<ProbeId>1A6F</ProbeId>
<ProbeValue ScaleUnit="mm">1245</ProbeValue>
</ProbeMsg>
import java.io.*;
import java.util.*;
import java.text.*;
import org.w3c.dom.*;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.apache.xerces.jaxp.DocumentBuilderFactoryImpl;
import org.apache.xerces.jaxp.DocumentBuilderImpl;
import org.apache.xml.serialize.XMLSerializer;
import org.apache.xml.serialize.OutputFormat;
public class ProbeMsg {
// XML tag's
private static final String TAG_PROBE_MSG = "ProbeMsg";
private static final String TAG_TIMESTAMP = "TimeStamp";
private static final String TAG_PROPE_ID = "ProbeId";
private static final String TAG_PROPE_VALUE = "ProbeValue";
// XML Settings
private static final String XML_VERSION = "1.0";
private static final String XML_ENCODING = "UTF-8";
// Format definitions
private static final String DATE_TIME_FORMAT =
"yyyy-MM-dd'T'HH:mm:ss'Z'";
// Variables
private Date msgTimeStamp = null;
private String probeId = "";
private Integer probeValue = null;
private Document xmlDoc = null;
private String xmlStr = null;
// Constructor
public ProbeMsg(Date pTimeStamp
,String pProbeId
,int pProbeValue ) {
this.msgTimeStamp = pTimeStamp;
this.probeId = pProbeId;
this.probeValue = new Integer(pProbeValue);
// Generate the XML Document using DOM
this.generateXMLDocument();
// Generate a XML String
this.generateXMLString();
}
// Retrive probe message as XML string
public String getXMLString() {
return xmlStr;
}
// Generate a DOM XML document
private void generateXMLDocument()
{
Element main;
Element root;
Element item;
DateFormat timeStampFormat =
new SimpleDateFormat( DATE_TIME_FORMAT );
try {
//Create a XML Document
DocumentBuilderFactory dbFactory =
DocumentBuilderFactoryImpl.newInstance();
DocumentBuilder docBuilder = dbFactory.newDocumentBuilder();
xmlDoc = docBuilder.newDocument();
} catch(Exception e) {
System.out.println("Error " + e);
}
// Create the root element
root = xmlDoc.createElement(TAG_PROBE_MSG);
// Add TimeStamp Element and its value
item = xmlDoc.createElement(TAG_TIMESTAMP);
item.appendChild(xmlDoc.createTextNode(
timeStampFormat.format(msgTimeStamp)));
root.appendChild(item);
// Add ProbeId Element and its value
item = xmlDoc.createElement(TAG_PROPE_ID);
item.appendChild(xmlDoc.createTextNode(probeId));
root.appendChild(item);
// Add ProbeValue Element and its value
item = xmlDoc.createElement(TAG_PROPE_VALUE);
item.appendChild(xmlDoc.createTextNode(probeValue.toString() ));
item.setAttribute("ScaleUnit", "mm");
root.appendChild(item);
// Add to the root Element
xmlDoc.appendChild(root);
}
// Generate String out of the XML document object
private void generateXMLString() {
StringWriter strWriter = null;
XMLSerializer probeMsgSerializer = null;
OutputFormat outFormat = null;
try {
probeMsgSerializer = new XMLSerializer();
strWriter = new StringWriter();
outFormat = new OutputFormat();
// Setup format settings
outFormat.setEncoding(XML_ENCODING);
outFormat.setVersion(XML_VERSION);
outFormat.setIndenting(true);
outFormat.setIndent(4);
// Define a Writer
probeMsgSerializer.setOutputCharStream(strWriter);
// Apply the format settings
probeMsgSerializer.setOutputFormat(outFormat);
// Serialize XML Document
probeMsgSerializer.serialize(xmlDoc);
this.xmlStr = strWriter.toString();
strWriter.close();
} catch (IOException ioEx) {
System.out.println("Error " + ioEx);
}
}
public static void main (String argv[]) {
ProbeMsg pMsg = new ProbeMsg(new Date() // Timestamp
,"1A6F" // Probe ID
,1245); // Probe Value
System.out.println(pMsg.getXMLString() );
}
}
javac -classpath ".;C:\java\xerces-1_4_3\xerces.jar" ProbeMsg.java
java -classpath ".;C:\java\xerces-1_4_3\xerces.jar" ProbeMsg
Logging: log4j http://jakarta.apache.org/log4j/docs/index.html
Xml dom: jdom http://www.jdom.org/
Xml parser and others: xerces http://xml.apache.org/
Download example above ProbeMsg.zip
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