Loop through all elements in XML using NodeList

Question

I want to loop through all elements in a piece of XML printing each one   My problem is that I keep getting a null pointer exception after the staff1 tag  i e  john 465456433 gmail1 area1 city1  This my Java code to print all elements in an xml file   File fXmlFile   new File  file 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        System out println  ----------------------------     Node n null  Element eElement null   for  int i   0  i  lt  nList getLength    i                   System out println nList getLength            n  nList item i                                 System out println   nCurrent Element      n getNodeName         if  n getNodeType      Node ELEMENT NODE        eElement    Element  n getChildNodes        System out println   nCurrent Element      n getNodeName         name   eElement getElementsByTagName  name   item i  getTextContent      here throws null pointer exception after printing staff1 tag     phone   eElement getElementsByTagName  phone   item i  getTextContent        email   eElement getElementsByTagName  email   item i  getTextContent        area   eElement getElementsByTagName  area   item i  getTextContent        city   eElement getElementsByTagName  city   item i  getTextContent          n getNextSibling        XML File    lt  xml version  1 0   gt   lt company gt     lt staff1 gt       lt name gt john lt  name gt       lt phone gt 465456433 lt  phone gt       lt email gt gmail1 lt  email gt       lt area gt area1 lt  area gt       lt city gt city1 lt  city gt     lt  staff1 gt     lt staff2 gt       lt name gt mary lt  name gt       lt phone gt 4655556433 lt  phone gt       lt email gt gmail2 lt  email gt       lt area gt area2 lt  area gt       lt city gt city2 lt  city gt     lt  staff2 gt     lt staff3 gt       lt name gt furvi lt  name gt       lt phone gt 4655433 lt  phone gt       lt email gt gmail3 lt  email gt       lt area gt area3 lt  area gt       lt city gt city3 lt  city gt     lt  staff3 gt   lt  company gt    Expected Output   john 465456433 gmail1 area1 city1 mary 4655556433 gmail2 area2 city2 furvi 4655433 gmail3 area3 city3

User · Answer

public class XMLParser      public static void main String   args         try            DocumentBuilder dBuilder   DocumentBuilderFactory newInstance   newDocumentBuilder             Document doc   dBuilder parse new File  xml input              NodeList nl doc getDocumentElement   getChildNodes              for int k 0 k lt nl getLength   k                  printTags  Node nl item k                       catch  Exception e     err handling             public static void printTags Node nodes          if nodes hasChildNodes       nodes getNodeType    3              System out println nodes getNodeName         nodes getTextContent                NodeList nl nodes getChildNodes               for int j 0 j lt nl getLength   j   printTags nl item j                      Recursively loop through and print out all the xml child tags in the document  in case you don t have to change the code to handle dynamic changes in xml  provided it s a well formed xml

User · Answer

DocumentBuilderFactory dbf   DocumentBuilderFactory newInstance        DocumentBuilder db   dbf newDocumentBuilder        Document dom   db parse  file xml        Element docEle   dom getDocumentElement        NodeList nl   docEle getChildNodes        int length   nl getLength        for  int i   0  i  lt  length  i              if  nl item i  getNodeType      Node ELEMENT NODE                Element el    Element  nl item i               if  el getNodeName   contains  staff                      String name   el getElementsByTagName  name   item 0  getTextContent                    String phone   el getElementsByTagName  phone   item 0  getTextContent                    String email   el getElementsByTagName  email   item 0  getTextContent                    String area   el getElementsByTagName  area   item 0  getTextContent                    String city   el getElementsByTagName  city   item 0  getTextContent                                    Iterate over all children and nl item i  getNodeType      Node ELEMENT NODE is used to filter text nodes out  If there is nothing else in XML what remains are staff nodes   For each node under stuff  name  phone  email  area  city    el getElementsByTagName  name   item 0  getTextContent       el getElementsByTagName  name   will extract the  name  nodes under stuff   item 0  will get you the first node and  getTextContent   will get the text content inside    Edit   Since we have jackson I would do this in a different way  Define a pojo for the object   public class Staff       private String name      private String phone      private String email      private String area      private String city     getters setters     Then using jackson       JsonNode root   new XmlMapper   readTree xml getBytes         ObjectMapper mapper   new ObjectMapper        root forEach node - gt  consume node  mapper       private void consume JsonNode node  ObjectMapper mapper        try           Staff staff   mapper treeToValue node  Staff class             TODO your job with staff       catch  JsonProcessingException e            e printStackTrace

User · Answer

Here is another way to loop through XML elements using JDOM           List lt Element gt  nodeNodes   inputNode getChildren            if  nodeNodes    null                for  Element nodeNode   nodeNodes                    List lt Element gt  elements   nodeNode getChildren elementName                   if  elements    null                        elements size                        nodeNodes removeAll elements

[java] Loop through all elements in XML using NodeList

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