I need to make a program which outputs the price of a specific element in an xml file.
The xml file looks like this:
<list name="root">
<book name="B1" price="30" isbn="123"/>
<list name="L1">
<book name="B2" price="20" isbn="234"/>
<list name="L2">
<cd name="C1" price="15"/>
<cd name="C2" price="5"/>
<book name="B3" price="10" isbn="345"/>
</list>
<cd name="C3" price="15"/>
<book name="B4" price="60" isbn="456"/>
</list>
</list>
My program should output something like this:
getPrice(B1) = 30;
getPrice(L1) = B2+L2+C3+B4 = 125 ...
My idea is to store the names and values in a hashmap, and then get the values from it. But, I have troubles getting the price for the nested lists. The program should work for different xml files as well. Only the types (cd, book and list) will be the same.
Here is my code so far:
public class ManageList implements Assignment7 {
private HashMap<String, Double> data = new HashMap<String, Double>();
#Override
public void loadXml(File input) throws Exception {
// given in the readme
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
// get filename => absolute path
String filename = input.getAbsolutePath();
Document doc = db.parse(new File(filename));
// Normalize the XML Structure
doc.getDocumentElement().normalize();
// get the root element from XML document
// Element root = doc.getDocumentElement();
// ####################################
// acces elements and their attributes and store it in a hashmap
// ####################################
NodeList nl = doc.getElementsByTagName("*");
storeNodes(nl);
//System.out.println(Arrays.asList(data));
}
#Override
public Optional<Double> getPrice(String item) {
return null;
}
public void storeNodes(NodeList nl) {
for (int i = 0; i < nl.getLength(); i++) {
Node n = nl.item(i);
int type = n.getNodeType();
if (type == Node.ELEMENT_NODE) {
Element e = (Element) n;
if (e.getTagName() == "book" || e.getTagName() == "cd") {
data.put(e.getAttribute("name"), Double.parseDouble(e.getAttribute("price")));
}
if (e.getTagName() == "list" && n.hasChildNodes()) {
String name = e.getAttribute("name");
//here i get a NumberFormatException
//data.put(name, Double.parseDouble(e.getAttribute("price")));
//just to show output
data.put(name, 0.0);
}
storeNodes(n.getChildNodes());
}
}
}
Hashmap output:
[{B2=20.0, C3=15.0, B3=10.0, B4=60.0, L1=0.0, L2=0.0, root=0.0, C1=15.0, B1=30.0, C2=5.0}]
How can I get the values for the nested Lists?
Thank you!
Since list contains sub attributes, looping from nList.getLength()-1 to 0 will avoid so many problems.
For list we need values(prices) of sub attributes book and cd. So looping from last to first will help us in storing the values of sub attributes in data as a prior step.
Now, For us to get total price of list, we iterate all over NodeList of books and cd.
we sum up all the values which makes the price of the list.
Below is the code if (e.getTagName() == "list" && n.hasChildNodes(),
NodeList books = e.getElementsByTagName("book");
NodeList cd = e.getElementsByTagName("cd");
System.out.println(books.getLength());
System.out.println(cd.getLength());
double listPrice = 0;
for(int i=0;i<books.getLength();i++) {
Node t = books.item(i);
Element e1 = (Element)t;
/**This can be reduced if we loop from nList.getLength()-1 to 0, Since the data already exists in data.
//if (!data.containsKey(e1.getAttribute("name"))){
// data.put(e1.getAttribute("name"),Double.parseDouble(e1.getAttribute("price")));
//
//}
*/
listPrice += Double.parseDouble(e1.getAttribute("price"));
}
for(int i=0;i<cd.getLength();i++){
Node t = cd.item(i);
Element e1 = (Element)t;
listPrice += Double.parseDouble(e1.getAttribute("price"));
}
for any doubts - comment.
Thanks.
Related
I have a xml file that looks like this.
<Device>
<Staff>
<Name>ABC</Name>
<Name>Hello</Name>
</Staff>
<Connect>
<Speed>123</Speed>
<Speed>456</Speed>
</Connect>
</Device>
I need help in retrieving the value of name & speed as i have never tried xml before. I am getting null pointer exception whenever I try to retrieve the element values. Any help is appreciated.
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
// Load the input XML document, parse it and return an instance of the
// Document class.
Document document = builder.parse(new File("C:/Users/AA/Desktop/eclipse/lol/testing.xml"));//change to own directory
NodeList nodeList = document.getDocumentElement().getChildNodes();
System.out.println(nodeList.getLength());
for (int i = 0; i < nodeList.getLength(); i++) {
Node node = nodeList.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {
System.out.println(i);
Element elem = (Element) node;
// Get the value of the ID attribute.
// String ID = node.getAttributes().getNamedItem("ID").getNodeValue();
// Get the value of all sub-elements.
String name = elem.getElementsByTagName("Name")
.item(0).getChildNodes().item(0).getNodeValue();
Integer speed = Integer.parseInt(elem.getElementsByTagName("Connect")
.item(0).getChildNodes().item(0).getNodeValue());//null pointer exception happens here
staffList.add(new staff(name));
connectList.add(new connect(speed));
}
}
// Print all employees.
for (staff stl : staffList)
{System.out.println("STAFF "+stl.getName());}
for (connect ctl : connectList)
{System.out.println("Connect "+ctl.getSpeed());}
You will have null pointer exceptions because you're assuming that in every iteration of the for loop, the desired nodes have children elements:
String name = elem.getElementsByTagName("Name")
.item(0).getChildNodes().item(0).getNodeValue();
In the above code, you are accessing the first child of a Name element which is a text node (e.g. ABC), and then getting its children nodes, which will cause an exception since there no children elements inside the text node.
Likewise,
Integer speed = Integer.parseInt(elem.getElementsByTagName("Connect")
.item(0).getChildNodes().item(0).getNodeValue());
will cause an exception in one of the iterations of the loop where elem corresponds to Connect itself.
You can try the following code instead:
if (node.getNodeType() == Node.ELEMENT_NODE) {
System.out.println(i);
Element elem = (Element) node;
// Get the value of the ID attribute.
// String ID =
// node.getAttributes().getNamedItem("ID").getNodeValue();
// Get the value of all sub-elements.
NodeList nameNodes = elem.getElementsByTagName("Name");
for(int j = 0; j < nameNodes.getLength(); j++) {
Node nameNode = nameNodes.item(j);
staffList.add(new staff(nameNode.getTextContent()));
}
NodeList speedNodes = elem.getElementsByTagName("Speed");
for(int j = 0; j < speedNodes.getLength(); j++) {
Node speedNode = speedNodes.item(j);
connectList.add(new connect(Integer.parseInt(speedNode.getTextContent())));
}
}
P.S.: Try to use class names that start with an uppercase.
You want getTextContent() rather than getNodeValue() - the latter always returns null for element nodes.
See: DOMDocument getNodeValue() returns null (contains an output escaped string)
How do I list the element names at a given level in an xml schema hierarchy? The code I have below is listing all element names at every level of the hierarchy, with no concept of nesting.
Here is my xml file:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><?xml-stylesheet type="text/xsl" href="CDA.xsl"?>
<SomeDocument xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="urn:something">
<title>some title</title>
<languageCode code="en-US"/>
<versionNumber value="1"/>
<recordTarget>
<someRole>
<id extension="998991"/>
<addr use="HP">
<streetAddressLine>1357 Amber Drive</streetAddressLine>
<city>Beaverton</city>
<state>OR</state>
<postalCode>97867</postalCode>
<country>US</country>
</addr>
<telecom value="tel:(816)276-6909" use="HP"/>
</someRole>
</recordTarget>
</SomeDocument>
Here is my java method for importing and iterating the xml file:
public static void parseFile() {
//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("D:\\mypath\\somefile.xml");
//get the root element
Element docEle = dom.getDocumentElement();
//get a nodelist of elements
NodeList nl = docEle.getElementsByTagName("*");
if (nl != null && nl.getLength() > 0) {
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {
System.out.println("node.getNodeName() is: "+node.getNodeName());
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
The output of the above program is:
title
languageCode
versionNumber
recordTarget
someRole
id
addr
streetAddressLine
city
state
postalCode
country
telecom
Instead, I would like to output the following:
title
languageCode
versionNumber
recordTarget
It would be nice to then be able to list the children of recordTarget as someRole, and then to list the children of someRole as id, addr, and telecom. And so on, but at my discretion in the code. How can I change my code to get the output that I want?
You're getting all nodes with this line:
NodeList nl = docEle.getElementsByTagName("*");
Change it to
NodeList nl = docEle.getChildNodes();
to get all of its children. Your print statement will then give you the output you're looking for.
Then, when you iterate through your NodeList, you can choose to call the same method on each Node you create:
NodeList children = node.getChildNodes();
If you want to print an XML-like structure, perhaps a recursive method that prints all child nodes is what you are looking for.
You could re-write the parseFile (I'd rather call it parseChildrenElementNames) method to take an input String that specifies the element name for which you want to print out its children element names:
public static void parseChildrenElementNames(String parentElementName) {
// 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("D:\\mypath\\somefile.xml");
// get the root element
NodeList elementsByTagName = dom.getElementsByTagName(parentElementName);
if(elementsByTagName != null) {
Node parentElement = elementsByTagName.item(0);
// get a nodelist of elements
NodeList nl = parentElement.getChildNodes();
if (nl != null) {
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {
System.out.println("node.getNodeName() is: "
+ node.getNodeName());
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
However, this will only consider the first element that matches the specified name.
For example, to get the list of elements under the first node named someRole, you would call parseChildrenElementNames("someRole"); which would print out:
node.getNodeName() is: id
node.getNodeName() is: addr
node.getNodeName() is: telecom
I need to get the tag of an element right below the root, but DOM seems only to offer methods getting child nodes (not elements) and you cant cast from one to the other.
http://ideone.com/SUjRmn
#Override
public void loadXml(String filepath) throws Exception {
File f = new File(filepath);
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = null;
Document doc = null;
try {
db = dbf.newDocumentBuilder();
} catch (ParserConfigurationException e) {
e.printStackTrace();
}
try {
doc = db.parse(f);
} catch (SAXException | IOException | NullPointerException e) {
e.printStackTrace();
}
Element root = doc.getDocumentElement();
Node firstChild = root.getFirstChild();
String tag = firstChild.getNodeName();
//here is the problem. I can't cast from Node to Element and Node
//stores only an int value, not the name of the object I want to restore
ShapeDrawer drawable = null;
switch (tag) {
case "scribble":
drawable = new ScribbleDrawer();
...
From the class to restore:
#Override
public void setValues(Element root) {
NodeList nodelist = null;
nodelist = root.getElementsByTagName("color");
colorManager.setColor((nodelist.item(0).getTextContent()));
this.color = colorManager.getCurrentColor();
System.out.println(color.toString());
nodelist = root.getElementsByTagName("pressx");
pressx = Integer.parseInt(nodelist.item(0).getTextContent());
System.out.println(pressx);
nodelist = root.getElementsByTagName("pressy");
pressy = Integer.parseInt(nodelist.item(0).getTextContent());
System.out.println(pressy);
nodelist = root.getElementsByTagName("lastx");
lastx = Integer.parseInt(nodelist.item(0).getTextContent());
nodelist = root.getElementsByTagName("lasty");
lasty = Integer.parseInt(nodelist.item(0).getTextContent());
}
public void toDOM(Document doc, Element root) {
System.out.println("ScribbleDrawer being saved");
Element shapeBranch = doc.createElement("scribble");
Attr attr1 = doc.createAttribute("hashcode");
attr1.setValue(((Integer) this.hashCode()).toString());
shapeBranch.setAttributeNode(attr1);
root.appendChild(shapeBranch);
Element eColor = doc.createElement("color");
eColor.setTextContent(colorManager.namedColorToString(color));
shapeBranch.appendChild(eColor);
// creating tree branch
Element press = doc.createElement("press");
Attr attr2 = doc.createAttribute("pressx");
attr2.setValue(((Integer) pressy).toString());
press.setAttributeNode(attr2);
Attr attr3 = doc.createAttribute("pressy");
attr3.setValue(((Integer) pressy).toString());
press.setAttributeNode(attr3);
shapeBranch.appendChild(press);
Element last = doc.createElement("last");
Attr attr4 = doc.createAttribute("lastx");
attr4.setValue(((Integer) lastx).toString());
last.setAttributeNode(attr4);
Attr attr5 = doc.createAttribute("lasty");
attr5.setValue(((Integer) lasty).toString());
last.setAttributeNode(attr5);
shapeBranch.appendChild(last);
}
I know other parsers are easier, but I am almost finished and when it comes to polymorphy JAXB seems to be just as complicated with Option-marshalling etc
EDIT: this is what the xml looks like; instead of "scribble" other tags/polymorphic children are possible which are deserialized from different instance variables (and thus different DOM-trees except for the root)
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Drawables>
<scribble hashcode="189680059">
<color>Black</color>
<press pressx="221" pressy="221"/>
<last lastx="368" lasty="219"/>
</scribble>
<scribble hashcode="1215837841">
<color>Black</color>
<press pressx="246" pressy="246"/>
<last lastx="368" lasty="221"/>
</scribble>
If your node is an Element, you can cast it from node to element. But your first child might also be a text node, which can't be cast, of course. You have to test the nodes for their NodeType before casting.
If your XML is not using namespaces, you can use a method like this one to extract your child elements. It receives a list of nodes, test each one and returns a list containing only the elements:
public static List getChildren(Element element) {
List<Element> elements = new ArrayList<>();
NodeList nodeList = element.getChildNodes();
for (int i = 0; i < nodeList.getLength(); i++) {
Node node = nodeList.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {
elements.add((Element) node);
}
}
return elements;
}
An alternative is to use an API which already includes such utility methods, like DOM4J, or JDOM.
I have to develop an android application.
Here i have follows following xml format.
<Product>
<product name="viki" productid="111">
<ProductType>
<producttype>Nokia</producttype>
<producttype>Samsung</producttype>
</ProductType>
</product>
</Product>
Here i have to get the producttype for particluar product.so i have wrote the following code:
if(subCategoryChildNode.hasChildNodes()){
// parse 'Subcategory' childs
NodeList productNL = subCategoryChildElmt.getElementsByTagName("product");
if(productNL.getLength() > 0){
ArrayList<Product> productAL = new ArrayList<Product>();
Product productBean = null;
for(int pCnt=0;pCnt<productNL.getLength();pCnt++){
Node productNode = productNL.item(pCnt);
Element productElmt = null;
// parse 'product' tag attributes
if(productNode.hasAttributes()){
productBean = new Product();
productElmt = (Element)productNode;
productBean.setmProductName(productElmt.getAttribute("name"));
}
if(productNode.hasChildNodes()){
NodeList productTypeNL = productElmt.getElementsByTagName("ProductType");
if(productTypeNL.getLength() > 0){
ArrayList<ProductType> ProductTypeAL = new ArrayList<ProductType>();
ProductType productTypeBean = null;
for(int ptCnt=0;ptCnt<productTypeNL.getLength();ptCnt++){
Node productTypeNode = productTypeNL.item(ptCnt);
Element productTypeElmt = null;
if(productTypeNode.hasChildNodes()){
productTypeBean = new ProductType();
productTypeElmt = (Element)productTypeNode;
productTypeBean.setmProductType(XMLfunctions.getValue(productTypeElmt,"producttype"));
System.out.println("Product Types are "+ " "+XMLfunctions.getValue(productTypeElmt,"producttype"));
ProductTypeAL.add(productTypeBean);
}
productBean.setmProductTypes(ProductTypeAL);
}
productAL.add(productBean);
}
}
subCategoryBean.setmProducts(productAL);
}
}
subCategoryAL.add(subCategoryBean);
}
Here am getting the value is nokia alone.but i need to display the value nokia,samsung...if i have to run the app means getting single value.but i need to get the list of all values..
What's wrong in my code .. please check and give me solution fot these ???
The reason you're getting only one <producttype> (Nokia) instead of the complete list because you're looping over the length of <ProductType> nodes thinking you're looping over the <producttype> ones.
So, you need another inner loop to cover all the child product type nodes like
for(int ptCnt=0; ptCnt < productTypeNL.getLength(); ptCnt++) {
Node productTypeNode = productTypeNL.item(ptCnt);
if(productTypeNode.hasChildNodes()){
NodeList childProductTypeNL = productTypeNode.getChildNodes();
System.out.print("Product Types are: ");
for (int cptCnt=0; cptCnt < childProductTypeNL.getLength(); cptCnt++) {
productTypeBean = new ProductType();
productTypeBean.setmProductType (
childProductTypeNL.item(cptCnt).getTextContent());
System.out.print(productTypeBean.getmProductType() + ", ");
ProductTypeAL.add(productTypeBean);
}
}
productBean.setmProductTypes(ProductTypeAL);
}
I've directly used the Node.getChildNodes() and Node.getTextContexnt() methods, instead of type casting to Element first and using its methods or the XMLfunctions utility class.
I also recommend using different names for child nodes instead of relying on using a different case to avoid such problems in future. A simple way to avoid name collision (when you're not able to come up with a different name) is to simply use a plural like <ProductTypes> for the parent tag.
However, a better approach when you need to parse deep within a DOM tree is to use an XPath to directly get the list of nodes you're interested in. I'm not entirely sure what the program does but just to give you an example an XPath like
String xpath = "//product[#name=\"viki\"]/ProductType/producttype";
would give you the NodeList for <producttype> nodes directly.
I'd say one of the problem of your code (might be others), is that you declare your productTypeBean and productTypeElmt before your for loop, and since it's not required after, it isn't needed.
if(subCategoryChildNode.hasChildNodes()){
// parse 'Subcategory' childs
NodeList productNL = subCategoryChildElmt.getElementsByTagName("product");
if(productNL.getLength() > 0){
ArrayList<Product> productAL = new ArrayList<Product>();
Product productBean = null;
for(int pCnt=0;pCnt<productNL.getLength();pCnt++){
Node productNode = productNL.item(pCnt);
Element productElmt = null;
// parse 'product' tag attributes
if(productNode.hasAttributes()){
productBean = new Product();
productElmt = (Element)productNode;
productBean.setmProductName(productElmt.getAttribute("name"));
}
if(productNode.hasChildNodes()){
NodeList productTypeNL = productElmt.getElementsByTagName("ProductType");
if(productTypeNL.getLength() > 0){
ArrayList<ProductType> ProductTypeAL = new ArrayList<ProductType>();
for(int ptCnt=0;ptCnt<productTypeNL.getLength();ptCnt++){
Node productTypeNode = productTypeNL.item(ptCnt);
if(productTypeNode.hasChildNodes()){
ProductType productTypeBean = new ProductType();
Element productTypeElmt = (Element)productTypeNode;
productTypeBean.setmProductType(XMLfunctions.getValue(productTypeElmt,"producttype"));
System.out.println("Product Types are "+ " "+XMLfunctions.getValue(productTypeElmt,"producttype"));
ProductTypeAL.add(productTypeBean);
}
productBean.setmProductTypes(ProductTypeAL);
}
productAL.add(productBean);
}
}
subCategoryBean.setmProducts(productAL);
}
}
subCategoryAL.add(subCategoryBean);
}
I am trying to get the all the authors from my xml file in jave here is the xml code
<?xml version="1.0"?>
<map>
<authors>
<author>testasdas</author>
<author>Test</author>
</authors>
</map>
Here is the code I'm using in Java
public static List<String> getAuthors(Document doc) throws Exception {
List<String> authors = new ArrayList<String>();
Element ed = doc.getDocumentElement();
if (notExists(ed, "authors")) throw new Exception("No authors found");
Node coreNode = doc.getElementsByTagName("authors").item(0);
if (coreNode.getNodeType() == Node.ELEMENT_NODE) {
Element coreElement = (Element) coreNode;
NodeList cores = coreElement.getChildNodes();
for (int i = 0; i < cores.getLength(); i++) {
Node node = cores.item(i);
if (node.getNodeType() == Node.ELEMENT_NODE) {
Element e = (Element) node;
String author = e.getElementsByTagName("author").item(i).getTextContent();
Bukkit.getServer().broadcastMessage("here");
authors.add(author);
}
}
}
return authors;
}
I am getting a java.lang.NullPointerException error when I try run the code but I'm not sure why.
09.04 17:05:24 [Server] SEVERE at com.dcsoft.arenagames.map.XMLHandler.getMapData(XMLHandler.java:42)
09.04 17:05:24 [Server] SEVERE at com.dcsoft.arenagames.map.XMLHandler.getAuthors(XMLHandler.java:73)
09.04 17:05:24 [Server] SEVERE java.lang.NullPointerException
The problem is that your code is indexing the <author> nodelist using i, which counts all children of the <authors> tag, some of which are not <author> elements. When item(i) returns null, you get a NPE when you try to call getTextContent(). You also don't need to do all that navigation (which looks kind of suspicious, and is certainly confusing). Try this instead:
public static List<String> getAuthors(Document doc) throws Exception {
List<String> authors = new ArrayList<String>();
NodeList authorNodes = doc.getElementsByTagName("author");
for (int i = 0; i < authorNodes.getLength(); i++) {
String author = authorNodes.item(i).getTextContent();
Bukkit.getServer().broadcastMessage("here");
authors.add(author);
}
return authors;
}
To find the cause of a java.lang.NullPointerException put a breakpoint on the line the exception occurred at, 73 in this case and investigate the variables on that line.
My guess is that in you line of code:
String author = e.getElementsByTagName("author").item(i).getTextContent()
the variable e is the author element and hence why e.getElementsByTagName("author") returns a null.