How to retrieve element value of XML using Java

Question

I am new to XML  I want to read the following XML on the basis of request name  Please help me on how to read the below XML in Java -   lt  xml version  1 0   gt       lt config gt           lt Request name  ValidateEmailRequest  gt               lt requestqueue gt emailrequest lt  requestqueue gt               lt responsequeue gt emailresponse lt  responsequeue gt           lt  Request gt           lt Request name  CleanEmail  gt               lt requestqueue gt Cleanrequest lt  requestqueue gt               lt responsequeue gt Cleanresponse lt  responsequeue gt           lt  Request gt       lt  config gt

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following links might help   http   labe felk cvut cz  xfaigl mep xml java-xml htm  http   developerlife com tutorials  p 25  http   www java-samples com showtutorial php tutorialid 152

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There are various APIs available to read write XML files through Java   I would refer using StaX  Also This can be useful - Java XML APIs

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There are a number of different ways to do this  You might want to check out XStream or JAXB  There are tutorials and the examples

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If the XML is well formed then you can convert it to Document  By using the XPath you can get the XML Elements  String xml    quot  lt stackusers gt  lt name gt Yash lt  name gt  lt age gt 30 lt  age gt  lt  stackusers gt  quot    Form XML-String Create Document and find the elements using its XML-Path  Document doc   getDocument xml  true        public static Document getDocument String xmlData  boolean isXMLData  throws Exception           DocumentBuilderFactory dbFactory   DocumentBuilderFactory newInstance            dbFactory setNamespaceAware true           dbFactory setIgnoringComments true           DocumentBuilder dBuilder   dbFactory newDocumentBuilder            Document doc          if  isXMLData                InputSource ips   new org xml sax InputSource new StringReader xmlData                doc   dBuilder parse ips             else               doc   dBuilder parse  new File xmlData                       return doc          Use org apache xpath XPathAPI to get Node or NodeList   System out println  quot XPathAPI  quot  getNodeValue doc   quot  stackusers age text   quot      NodeList nodeList   getNodeList doc   quot  stackusers quot    System out println  quot XPathAPI NodeList  quot   getXmlContentAsString nodeList    System out println  quot XPathAPI NodeList  quot   getXmlContentAsString nodeList item 0          public static String getNodeValue Document doc  String xpathExpression  throws Exception           Node node   org apache xpath XPathAPI selectSingleNode doc  xpathExpression           String nodeValue   node getNodeValue            return nodeValue            public static NodeList getNodeList Document doc  String xpathExpression  throws Exception           NodeList result   org apache xpath XPathAPI selectNodeList doc  xpathExpression           return result          Using javax xml xpath XPathFactory  System out println  quot javax xml xpath XPathFactory  quot  getXPathFactoryValue doc   quot  stackusers age quot          static XPath xpath   javax xml xpath XPathFactory newInstance   newXPath        public static String getXPathFactoryValue Document doc  String xpathExpression  throws XPathExpressionException  TransformerException  IOException           Node node    Node  xpath evaluate xpathExpression  doc  XPathConstants NODE           String nodeStr   getXmlContentAsString node           return nodeStr          Using Document Element   System out println  quot DocumentElementText  quot  getDocumentElementText doc   quot age quot          public static String getDocumentElementText Document doc  String elementName            return doc getElementsByTagName elementName  item 0  getTextContent            Get value in between two strings   String nodeVlaue   org apache commons lang StringUtils substringBetween xml   quot  lt age gt  quot    quot  lt  age gt  quot    System out println  quot StringUtils substringBetween    quot  nodeVlaue    Full Example  public static void main String   args  throws Exception       String xml    quot  lt stackusers gt  lt name gt Yash lt  name gt  lt age gt 30 lt  age gt  lt  stackusers gt  quot       Document doc   getDocument xml  true            String nodeVlaue   org apache commons lang StringUtils substringBetween xml   quot  lt age gt  quot    quot  lt  age gt  quot        System out println  quot StringUtils substringBetween    quot  nodeVlaue            System out println  quot DocumentElementText  quot  getDocumentElementText doc   quot age quot         System out println  quot javax xml xpath XPathFactory  quot  getXPathFactoryValue doc   quot  stackusers age quot              System out println  quot XPathAPI  quot  getNodeValue doc   quot  stackusers age text   quot         NodeList nodeList   getNodeList doc   quot  stackusers quot        System out println  quot XPathAPI NodeList  quot   getXmlContentAsString nodeList        System out println  quot XPathAPI NodeList  quot   getXmlContentAsString nodeList item 0       public static String getXmlContentAsString Node node  throws TransformerException  IOException       StringBuilder stringBuilder   new StringBuilder        NodeList childNodes   node getChildNodes        int length   childNodes getLength        for  int i   0  i  lt  length  i              stringBuilder append  toString childNodes item i   true               return stringBuilder toString       OutPut  StringUtils substringBetween   30 DocumentElementText 30 javax xml xpath XPathFactory 30 XPathAPI 30 XPathAPI NodeList  lt stackusers gt      lt name gt Yash lt  name gt      lt age gt 30 lt  age gt   lt  stackusers gt  XPathAPI NodeList  lt name gt Yash lt  name gt  lt age gt 30 lt  age gt

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In case you just need one  first  value to retrieve from xml     public static String getTagValue String xml  String tagName       return xml split   lt   tagName   gt    1  split   lt    tagName   gt    0       In case you want to parse whole xml document use JSoup   Document doc   Jsoup parse xml      Parser xmlParser     for  Element e   doc select  Request          System out println e

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Since you are using this for configuration  your best bet is apache commons-configuration  For simple files it s way easier to use than  raw  XML parsers   See the XML how-to

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You can make a class which extends org xml sax helpers DefaultHandler and call  start  lt tag name gt  Attributes attrs     and  end  lt tag name gt       For  it is   start request queue attrs     etc   And then extends that class and implement xml configuration file parsers you want  Example            public void startElement String uri  String name  String qname                             org xml sax Attributes attrs                     throws org xml sax SAXException       Class   args   new Class 2       args 0    uri getClass        args 1    org xml sax Attributes class      try         String mname   name replace  -              java lang reflect Method m                getClass   getDeclaredMethod  start    mname  args         m invoke this  new Object     uri   org xml sax Attributes attrs                catch  IllegalAccessException e          throw new RuntimeException e             catch  NoSuchMethodException e          throw new RuntimeException e            catch  java lang reflect InvocationTargetException e          org xml sax SAXException se                new org xml sax SAXException e getTargetException           se setStackTrace e getTargetException   getStackTrace             and in a particular configuration parser       public void start Request String uri  org xml sax Attributes attrs            make sure to read attributes correctly      System err println  Request  name    attrs getValue 0

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If your XML is a String  Then you can do the following   String xml         Populated XML String      DocumentBuilderFactory factory   DocumentBuilderFactory newInstance    DocumentBuilder builder   factory newDocumentBuilder    Document document   builder parse new InputSource new StringReader xml     Element rootElement   document getDocumentElement      If your XML is in a file  then Document document will be instantiated like this   Document document   builder parse new File  file xml       The document getDocumentElement   returns you the node that is the document element of the document  in your case  lt config gt     Once you have a rootElement  you can access the element s attribute  by calling rootElement getAttribute   method   etc  For more methods on java s org w3c dom Element  More info on java DocumentBuilder  amp  DocumentBuilderFactory  Bear in mind  the example provided creates a XML DOM tree so if you have a huge XML data  the tree can be huge    Related question      Update Here s an example to get  value  of element  lt requestqueue gt   protected String getString String tagName  Element element            NodeList list   element getElementsByTagName tagName           if  list    null  amp  amp  list getLength    gt  0                NodeList subList   list item 0  getChildNodes                 if  subList    null  amp  amp  subList getLength    gt  0                    return subList item 0  getNodeValue                                     return null          You can effectively call it as    String requestQueueName   getString  requestqueue   element

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If you are just looking to get a single value from the XML you may want to use Java s XPath library   For an example see my answer to a previous question    How to use XPath on xml docs having default namespace   It would look something like   import javax xml parsers DocumentBuilder  import javax xml parsers DocumentBuilderFactory  import javax xml xpath XPath  import javax xml xpath XPathConstants  import javax xml xpath XPathFactory   import org w3c dom Document  import org w3c dom NodeList   public class Demo        public static void main String   args            DocumentBuilderFactory domFactory   DocumentBuilderFactory newInstance            try               DocumentBuilder builder   domFactory newDocumentBuilder                Document dDoc   builder parse  E  test xml                 XPath xPath   XPathFactory newInstance   newXPath                Node node    Node  xPath evaluate   Request  name   dDoc  XPathConstants NODE               System out println node getNodeValue               catch  Exception e                e printStackTrace

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There are two general ways of doing that  You will either create a Domain Object Model of that XML file  take a look at this  and the second choice is using event driven parsing  which is an alternative to DOM xml representation  Imho you can find the best overall comparison of these two basic techniques here  Of course there are much more to know about processing xml  for instance if you are given XML schema definition  XSD   you could use JAXB

[java] How to retrieve element value of XML using Java?

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