Develop Reference

Nested loop creates duplicate entries when ran, cannot find issue?

When the code is ran the nested loop causes it to create occasional duplicate entries to the system, i have spent a while looking through this but still cant find what is causing this, would greatly appreciate any help?
for(int i = 0; i < subWorkItemElement.getChildNodes().getLength(); i++) {
Boolean test = false;
WorkItemCommon existingChild = null;
String summary = null;
if(subWorkItemElement.getChildNodes().item(i).getNodeName().equals("workitem")) {
// We know it's a work item - but is it in the existing list?
Element childWorkItem = (Element) subWorkItemElement.getChildNodes().item(i);
for(int j = 0; j < subWorkItemElement.getChildNodes().getLength(); j++) {
if(childWorkItem.getChildNodes().item(j) instanceof Element) {
if(((Element)childWorkItem.getChildNodes().item(j)).getNodeName().equals("details")) {
summary = ((Element) childWorkItem.getChildNodes().item(j)).getElementsByTagName("summary")
.item(0).getTextContent();
for(String k : userInfoHashMap.keySet()) {
summary = summary.replace("${" + k + "}", userInfoHashMap.get(k));
}
if(childHashTable.containsKey(summary)) {
test = true;
existingChild = childHashTable.get(summary);
IWorkItem workItem = existingChild.getWorkItem();
System.out.println("INFO: The task with summary \"" + summary + "\" already exists. Skipping creation.");
System.out.println("this task is work item: " + workItem.getId());
//either check the tasks in the xml for updated details and then modify the existing workitem
//or just modify the work item without checking for updates
makeChildTask(childWorkItem, existingChild, childHashTable, userInfoHashMap, workItemHashMap, rtc, false);
break;
}
}
}
}
if(!test) {
System.out.println("INFO: The task with summary " + summary + " does not currently exist. Creating.");
makeChildTask(childWorkItem, thisItem, childHashTable, userInfoHashMap, workItemHashMap, rtc, true);
} else makeFromExistingChildTask(childWorkItem, existingChild, userInfoHashMap, workItemHashMap, rtc);
}
}

You are possibly (not sure what makeChildTask() does) changing an XML structure while iterating through the children list. While not necessarily incorrect, this can mean you get entries inserted while you process the list. Since you call the subWorkItemElement.getChildNodes().getLength() each time instead of cache'ing it, this might result in the length changing in between the loop iterations.

Reading XML tags in java, code optimization

What I am actually doing is a recursive function which reads the tags in the xml. Below is the code:
private void readTag(org.w3c.dom.Node item, String histoTags, String fileName, Hashtable<String, String> tagsInfos) {
try {
if (item.getNodeType() == Node.ELEMENT_NODE) {
NodeList itemChilds = item.getChildNodes();
for (int i=0; i < itemChilds.getLength(); i++) {
org.w3c.dom.Node itemChild = itemChilds.item(i);
readTag(itemChild, histoTags + "|" + item.getNodeName(), fileName, tagsInfos);
}
}
else if (item.getNodeType() == Node.TEXT_NODE) {
tagsInfosSoft.put(histoTags, item.getNodeValue());
}
}
This function takes some time to execute. The xml the function reads is in this format:
<?xml version="1.0" encoding="UTF-8"?>
<Document>
<Mouvement>
<Com>
<IdCom>32R01000000772669473</IdCom>
<RefCde>32R</RefCde>
<Edit>0</Edit>
<Com>
<Mouvement>
<Document>
Is there any way of optimizing this code in java?

Two optimizations, don't know how much they will help:
Don't use getChildNodes(). Use getFirstChild() and getNextSibling().
Reuse a single StringBuilder instead of creating a new one for every element (implicitly done by histoTags + "|" + item.getNodeName()).
But, you should also be aware that the text content of an element node may seen as a combination of multiple TEXT and CDATA nodes.
Your code will also work better if it works on elements, not nodes.
private static void readTag(Element elem, StringBuilder histoTags, String fileName, Hashtable<String, String> tagsInfos) {
int histoLen = histoTags.length();
CharSequence textContent = null;
boolean hasChildElement = false;
for (Node child = elem.getFirstChild(); child != null; child = child.getNextSibling()) {
switch (child.getNodeType()) {
case Node.ELEMENT_NODE:
histoTags.append('|').append(child.getNodeName());
readTag((Element)child, histoTags, fileName, tagsInfos);
histoTags.setLength(histoLen);
hasChildElement = true;
break;
case Node.TEXT_NODE:
case Node.CDATA_SECTION_NODE:
//uncomment to test: System.out.println(histoTags + ": \"" + child.getTextContent() + "\"");
if (textContent == null)
// Optimization: Don't copy to a StringBuilder if only one text node will be found
textContent = child.getTextContent();
else if (textContent instanceof StringBuilder)
// Ok, now we need a StringBuilder to collect text from multiple nodes
((StringBuilder)textContent).append(child.getTextContent());
else
// And we keep collecting text from multiple nodes
textContent = new StringBuilder(textContent).append(child.getTextContent());
break;
default:
// ignore all others
}
}
if (textContent != null) {
String text = textContent.toString();
// Suppress pure whitespace content on elements with child elements, i.e. structural whitespace
if (! hasChildElement || ! text.trim().isEmpty())
tagsInfos.put(histoTags.toString(), text);
}
}
Test
String xml = "<root>\n" +
" <tag>hello <![CDATA[world]]> Foo <!-- comment --> Bar</tag>\n" +
"</root>\n";
Element docElem = DocumentBuilderFactory.newInstance()
.newDocumentBuilder()
.parse(new InputSource(new StringReader(xml)))
.getDocumentElement();
Hashtable<String, String> tagsInfos = new Hashtable<>();
readTag(docElem, new StringBuilder(docElem.getNodeName()), "fileName", tagsInfos);
System.out.println(tagsInfos);
Output (with print uncommented)
root: "
"
root|tag: "hello "
root|tag: "world"
root|tag: " Foo "
root|tag: " Bar"
root: "
"
{root|tag=hello world Foo Bar}
See how splitting the text inside the <tag> node using CDATA and comments caused the DOM node to contain multiple TEXT/CDATA child nodes.

.getTextContent returns text from child elements too

I'm trying to get XML parsing down (and yes I know there's easier ways to parse/validate like xstream) but I can't seem to get text content of just a single element. For example:
<container>
<element0>textThatIWant</element0> //only returned by .getTextContent
<element1>
<subelement0>textThatIDontWant</subelement0> //but also returned by
<subelement1>textThatIDontWant</subelement1> //.getTextContent
</element1>
<container>
I'm piping results out to the console and get mostly what I'm looking for but the only way I seem to get the text strings is with .getTextContent() which returns all text in the sub elements, as well, without whitespace (or else I'd have split on spaces) or .getNodeValue().toString() which throws nullPointerExceptions. #Jihar mentioned something like .getTextValue() but Eclipse doesn't recognize it (maybe there's something I can implement/inherit/whatever to add capability), any help?
Here's the code I'm using:
import javax.xml.parsers.*;
import org.w3c.dom.*;
import org.xml.sax.SAXException;
import java.io.*;
public class Test {
public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
StringBuilder xmlStringBuilder = new StringBuilder();
String appendage = "..." //This string holds the xml formatted data I'll be
//using in a long annoying line, I'll include it
//separately for clarity
xmlStringBuilder.append(appendage);
ByteArrayInputStream input = new ByteArrayInputStream(xmlStringBuilder.toString().getBytes("UTF-8"));
System.out.println("Test Results:");
System.out.println();
Document doc = builder.parse(input);
Element root = doc.getDocumentElement();
NodeList children = root.getChildNodes();
System.out.println(root.getTagName());
System.out.println();
for (int i = 0; i < children.getLength(); i++) {
Node child = children.item(i);
if (child instanceof Element) {
Element childElement = (Element) child;
System.out.println(childElement.getTagName() + " " + childElement);
NodeList grandChildren = child.getChildNodes();
for (int x = 0; x < grandChildren.getLength(); x++) {
Node grandChild = grandChildren.item(x);
if (grandChild instanceof Element) {
Element grandChildElement = (Element) grandChild;
System.out.print("\t" + grandChildElement.getTagName() + ":\t");
NodeList greatGrandChildren = grandChild.getChildNodes();
for (int y = 0; y < greatGrandChildren.getLength(); y++) {
Node greatGrandChild = greatGrandChildren.item(y);
if (greatGrandChild instanceof Element) {
Element greatGrandChildElement = (Element) greatGrandChild;
System.out.print(" " + greatGrandChildElement.getTextContent());
if ( y < greatGrandChildren.getLength() - 1) { System.out.print(","); } }
}
System.out.println();
}
}
}
}
}
}
And here's the appendage variable in full:
String appendage = "<?xml version=\"1.0\"?><branch0><name>business</name><taxINFO/><personnel><executives><name>Billy Bob</name><name>Colonel Jessup</name></executives><managerial/><operations><name>sabrina</name><name>lisa</name></operations><services><name>jamie</name><name>justin</name><name>forest</name></services></personnel><regions><ebay><area>OK</area><area>BE</area><area>EV</area><area>WC</area></ebay><sbay><area>SJ</area><area>MP</area><area>SV</area><area>MV</area></sbay><S.F.><area>SF</area></S.F.><N.Y.><area>NY</area></N.Y.><S.CA><area>SD</area><area>LA</area></S.CA></regions><products/><services/></branch0>";
or:
String appendage = "
<?xml version=\"1.0\"?>
<branch0>
<name>business</name>
<taxINFO/>
<personnel>
<executives>
<name>Billy Bob</name>
<name>Colonel Jessup</name>
</executives>
<managerial/>
<operations>
<name>sabrina</name>
<name>lisa</name>
</operations>
<services>
<name>jamie</name>
<name>justin</name>
<name>forest</name>
</services>
</personnel>
<regions>
<ebay>
<area>OK</area>
<area>BE</area>
<area>EV</area>
<area>WC</area>
</ebay>
<sbay>
<area>SJ</area>
<area>MP</area>
<area>SV</area>
<area>MV</area>
</sbay>
<S.F.>
<area>SF</area>
</S.F.>
<N.Y.>
<area>NY</area>
</N.Y.>
<S.CA>
<area>SD</area>
<area>LA</area>
</S.CA>
</regions>
<products/>
<services/>
</branch0>";
";
And, finally my console output (which you'll see is stating [name: null] where I'd like it to say something like [name: business] or even just business; but not include the sub element data w/out whitespace):
Test Results:
branch0
name [name: null]
taxINFO [taxINFO: null]
personnel [personnel: null]
executives: Billy Bob, Colonel Jessup
managerial:
operations: sabrina, lisa
services: jamie, justin, forest
regions [regions: null]
ebay: OK, BE, EV, WC
sbay: SJ, MP, SV, MV
S.F.: SF
N.Y.: NY
S.CA: SD, LA
products [products: null]
services [services: null]
and here's my console output using .getTextContent:
Test Results:
business
branch0
name business
taxINFO
personnel Billy BobColonel Jessupsabrinalisajamiejustinforest
executives: Billy Bob, Colonel Jessup
managerial:
operations: sabrina, lisa
services: jamie, justin, forest
regions OKBEEVWCSJMPSVMVSFNYSDLA
ebay: OK, BE, EV, WC
sbay: SJ, MP, SV, MV
S.F.: SF
N.Y.: NY
S.CA: SD, LA
products
services

System.out.println(childElement.getTagName() + " " + childElement);
should be (as you actually know!)
System.out.println(childElement.getTagName() + " "
+ childElement.getTextContent());

So, for my purposes, I was able to get the individual elements I was looking for using an XPath:
XPathFactory xpfactory = XPathFactory.newInstance();
XPath path = xpfactory.newXPath();
try {
String aString = path.evaluate("/branch0/name", doc);
System.out.println(aString);
} catch (XPathExpressionException e) { e.printStackTrace(); }
Of course this requires pre-existing knowledge of the structure, but since I can validate with an XML Schema and my docs are not too complicated/heavily nested I don't think that will be an issue for me. When I finish working on my current project I'll try to look up and post links about iterating over the child nodes and checking for text nodes (as #Ian Roberts suggested) but I don't know enough about XML to do that now.

Add logs and sysout

I have been asked to add logs and sysout before the class declaration.What logs should I use and how to add Sysout??What is the significance of adding these in this program?Also I am asked to create constant field for Staff Id and first name.Does that mean I should create constant variables that will store staff id and first name??
public class Read {
public static void main(String argv[]) {
try {
File fXmlFile = new File("/Users/mkyong/staff.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);
doc.getDocumentElement().normalize();
System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("staff");
System.out.println("----------------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
System.out.println("\nCurrent Element :" + nNode.getNodeName());
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Staff id : " + eElement.getAttribute("id"));
System.out.println("First Name : " + eElement.getElementsByTagName("firstname").item(0).getTextContent());
System.out.println("Last Name : " + eElement.getElementsByTagName("lastname").item(0).getTextContent());
System.out.println("Nick Name : " + eElement.getElementsByTagName("nickname").item(0).getTextContent());
System.out.println("Salary : " + eElement.getElementsByTagName("salary").item(0).getTextContent());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

I assume that by Sysout they mean System.out.println and as I can see, you have already added those.
By logs I assume it is meant using a logging implementation. An example of using java.utils.logging.Logger is this:
import java.util.logging.Logger;
public class Main {
private static Logger LOGGER = Logger.getLogger(Main.class.getSimpleName());
public static void main(String[] args) {
LOGGER.info("Logging an INFO-level message");
}
}
As you can see, some of a Logger's purpose is to output text that is using for diagnosing (debugging, monitoring). It can output the text to a console, file, database and it formats it in whatever way you want.
Using a logger vs plain System.out.println offers a lot more power and control.
Also I am asked to create constant field for Staff Id and first name
You got the idea here. It means creating constants for "firstname", "staff", "lastname" and any other string. Then, where you need to use that string you use the constant:
Ex:
private static final String STAFF = "staff";
private static final String FIRST_NAME = "firstname";
The advantage of doing so is that you can see all your constants in a single place and easily modify them when you need to. Imagine using "firstname" in 5 places. Than you realize you meant to use "first_name" instead. If you don't use constants you would have to change it in 5 places, else, just in 1 place.

"you have been asked", When your homework is not clear you should ask your TA first.
Besides, "/Users/mkyong/staff.xml" looks very very suspicious to me. since mkyong is a very famous developper. You should not take examples from the internet and copy/paste them without understanding them.
That said, yes you should declare static final fields to be constants, such as
private static final String STAFF_ID = "Staff id"
private static final String FIRST_NAME = "First Name"
and then replace those values in your code.
As for logging and sysout, sysout just means adding
System.out.println("something you would like to print")
Logging does the same thing but using a framework and giving more information automatically, such as the time the line was printed and which class triggered the print It also gives flexibility on when to print messages.
See this first
http://en.wikipedia.org/wiki/Java_logging_framework

A better way to do XML in Java

There are a lot of questions that ask the best XML parser, I am more interested in what is the XML parser that is the most like Groovy for Java?
I want:
SomeApiDefinedObject o = parseXml( xml );
for( SomeApiDefinedObject it : o.getChildren() ) {
System.out.println( it.getAttributes() );
}
The most important things are that I don't want to create a class for every type of XML node, I'd rather just deal with them all as strings, and that building the XML doesn't require any converters or anything, just a simple object that is already defined
If you have used the Groovy XML parser, you will know what I'm talking about
Alternatively, would it be better for me to just use Groovy from Java?

Here is something quick you can do with Sun Java Streaming XML Parser
FileInputStream xmlStream = new FileInputStream(new File("myxml.xml"));
XMLStreamReader reader = XMLInputFactory.newInstance().createXMLStreamReader(xmlStream);
while(reader.hasNext()){
reader.next();
for(int i=0; i < reader.getAttributeCount(); i++) {
System.out.println(reader.getAttributeName(i) + "=" + reader.getAttributeValue(i));
}
}

I would like to shamelessly plug the small open-source library I have written to make parsing XML in Java a breeze.
Check out Jinq2XML.
http://code.google.com/p/jinq2xml/
Some sample code would look like:
Jocument joc = Jocument.load(urlOrStreamOrFileName);
joc.single("root").children().each(new Action() {
public void act(Jode j){
System.out.println(j.name() + ": " + j.value());
}
});

Looks like all you want is a simple DOM API, such as provided by dom4j. There actually already a DOM API in the Standard Library (the org.w3c.dom packages), but it's only the API, so you need a separate implementation - might as well use something a little more advanced like dom4j.

Use Groovy.
It seems that your primary goal is to be able to access the DOM in a "natural" way via object accessors, and Java won't let you do this without defining classes. Groovy, because it is "duck typed," will allow you to do this.
The only reason not to use Groovy is if (1) XML processing is a very small part of your application, and/or (2) you have to work with other people who may want to program strictly in Java.
Whatever you do, do not decide to "just deal with them all as strings." XML is not a simple format, and unless you know the spec inside and out, you're not likely to get it right. Which means that your XML will be rejected by spec-conformant parsers.

I highly recommend JAXB. Great for XML <--> Java objects framework.

There used to be a very small and simple XML parser called NanoXML. It seems not to be developed anymore, but it's still available at http://devkix.com/nanoxml.php

I have good experiences with XStream. It's fairly quick and will serialize and deserialize Java to/from XML with no schema and very little code It Just Works™. The Java object hierarchies it builds will directly mirror your XML.

I work with Dozer and Castor for getting OTOM (Object to Object Mapping).

Try This code!!!!!
import org.w3c.dom.*;
import org.xml.sax.SAXException;
import javax.xml.parsers.*;
import javax.xml.transform.Transformer;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.*;
import javax.xml.*;
import java.io.File;
import java.io.IOException;
public class XmlDemo {
public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException
{
// Get Document Builder
// Get Document Builder
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
//Build Document
Document document = builder.parse(new File("D:/test.xml"));
//Normalize the XML Structure; It's just too important !!
document.getDocumentElement().normalize();
//Here comes the root node
Element root = document.getDocumentElement();
System.out.println(root.getNodeName());
//Get all employees
NodeList nList = document.getElementsByTagName("company");
System.out.println(nList.getLength());
System.out.println("============================");
visitChildNodes(nList);
}
//This function is called recursively
private static void visitChildNodes(NodeList nList)
{
Node tempNode = null;
// System.out.println("The Number of child nodes are " + (nList.getLength()) );
if(!(nList.getLength() == 1)) {
// System.out.println("The Number of child nodes are " + (nList.getLength()) );
// for (int temp = 0; temp < nList.getLength(); temp++)
// {
// Node node = nList.item(temp);
// if (node.getNodeType() == Node.ELEMENT_NODE)
// {
// System.out.println();
// System.out.println("Node Name = " + node.getNodeName() + ";");
// }
// }
}
for (int temp = 0; temp < nList.getLength(); temp++)
{
Node node = nList.item(temp);
if (node.getNodeType() == Node.ELEMENT_NODE)
{
System.out.println();
System.out.println("Node Name = " + node.getNodeName() + ";");
// if (node.hasAttributes()) {
// // get attributes names and values
// NamedNodeMap nodeMap = node.getAttributes();
// for (int i = 0; i < nodeMap.getLength(); i++)
// {
// tempNode = nodeMap.item(i);
// System.out.println(" Attr : " + tempNode.getNodeName()+ "; Value = " + tempNode.getNodeValue());
// }
//
// }else {
//// System.out.println("No Attributes");
// }
if (node.hasChildNodes()) {
NodeList nodeList = node.getChildNodes();
if((node.getChildNodes().getLength()/2)>0) {
System.out.println("This node has child nodes "+ (node.getChildNodes().getLength()/2));
System.out.println("Child nodes of : [ " + node.getNodeName() + " ] =>");
for(int k = 0;k < nodeList.getLength(); k++) {
Node n = nodeList.item(k);
if (n.getNodeType() == Node.ELEMENT_NODE)
{
if((k<(nodeList.getLength()))) {
System.out.println(" [ " + n.getNodeName() + " ] =>" );
if (n.hasAttributes()) {
// // get attributes names and values
NamedNodeMap nodeMap = n.getAttributes();
for (int i = 0; i < nodeMap.getLength(); i++)
{
tempNode = nodeMap.item(i);
System.out.println(" Attr : " + tempNode.getNodeName()+ "; Value = " + tempNode.getNodeValue() + " ]");
}
}else {
// System.out.println("No Attributes");
}
}else if((k==(nodeList.getLength()))) {
System.out.println(" [ " + n.getNodeName() + " ]");
}
}
}
System.out.println(" ]");
}
visitChildNodes(node.getChildNodes());
}
}
}
}
}
enter code here