Xml or extended markup language is a markup language made of many tag which are both readable by humans and machine, it has a tree structure with a root node, many branches and leaves.
Xml can respect a set of rules defined in two ways: the old DTD (Document Type Definition) and the more recent XML schema.
XML is useful for the below purposes
- Web services SOAP use the XML for the communication between the two involved endpoints and for their main configuration file (WSDL)
- making the communication between different software, it’s much better than the CSV (Comma separated value) because being hierarchically an xml document can be easily converted in an object (that’s called “Marshalling”) and vice-versa (“Un-Marshalling”)
- Storing configuration information: the application descriptor web.xml, the JSF configuration file faces-config.xml, the struts config file, the hibernate config file are just few examples about XML configurations file.
the only problem of the xml is that it’s redundant so every opened tag should be closed and the tag name is replicated two times
<tag_name> tag value <tag_name>
if the tag name is huge and it has not value so we transmit on line many characters with no value
A better format is the JSON which can be converted to an object but it replaces tags with parenthesis, so it’s not replicated any information.
How to process an XML file using Java?
We need to parse it using XPath and to add a node everywhere.
XPATH
let’s try to inquire the below xml
<?xml version="1.0" encoding="UTF-8"?> <Employees> <Employee id="1"> <age>29</age> <name>Pankaj</name> <gender>Male</gender> <role>Java Developer</role> </Employee> <Employee id="2"> <age>35</age> <name>Lisa</name> <gender>Female</gender> <role>CEO</role> </Employee> <Employee id="3"> <age>40</age> <name>Tom</name> <gender>Male</gender> <role>Manager</role> </Employee> <Employee id="4"> <age>25</age> <name>Meghna</name> <gender>Female</gender> <role>Manager</role> </Employee> </Employees>
private static List<String> getFemaleEmployeesName(Document doc, XPath xpath) {
List<String> list = new ArrayList<>();
try {
//create XPathExpression object
XPathExpression expr =
xpath.compile("/Employees/Employee[gender='Female']/name/text()");
//evaluate expression result on XML document
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++)
list.add(nodes.item(i).getNodeValue());
} catch (XPathExpressionException e) {
e.printStackTrace();
}
return list;
}
private static List<String> getEmployeeNameWithAge(Document doc, XPath xpath, int age) {
List<String> list = new ArrayList<>();
try {
XPathExpression expr =
xpath.compile("/Employees/Employee[age>" + age + "]/name/text()");
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++)
list.add(nodes.item(i).getNodeValue());
} catch (XPathExpressionException e) {
e.printStackTrace();
}
return list;
}
private static String getEmployeeNameById(Document doc, XPath xpath, int id) {
String name = null;
try {
XPathExpression expr =
xpath.compile("/Employees/Employee[@id='" + id + "']/name/text()");
name = (String) expr.evaluate(doc, XPathConstants.STRING);
} catch (XPathExpressionException e) {
e.printStackTrace();
}
return name;
}
Below is the method to add a node in the name of a female employer
private static List<String> addNodesInsideFemaleEmployeesName(Document doc, XPath xpath) {
List<String> list = new ArrayList<>();
try {
//create XPathExpression object
XPathExpression expr =
xpath.compile("/Employees/Employee[gender='Female']/name/text()");
//evaluate expression result on XML document
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++){
Element node = doc.createElement("New_Node"+i);
Element nodeInside = doc.createElement("newnodeInside");
nodeInside.setTextContent("This is the content"); //adds content
nodeInside.setAttribute("attrib", "attrib_value"); //adds an attribute
node.appendChild(nodeInside);
nodes.item(i).getParentNode().insertBefore(node, nodes.item(i).getNextSibling());
}
} catch (XPathExpressionException e) {
e.printStackTrace();
}
return list;
}
below is the result
<?xml version="1.0" encoding="UTF-8" standalone="no"?> <Employees> <Employee id="1"> <age>29</age> <name>Pankaj</name> <gender>Male</gender> <role>Java Developer</role> </Employee> <Employee id="2"> <age>35</age> <name>Lisa<New_Node0> <newnodeInside attrib="attrib_value">This is the content</newnodeInside> </New_Node0> </name> <gender>Female</gender> <role>CEO</role> </Employee> <Employee id="3"> <age>40</age> <name>Tom</name> <gender>Male</gender> <role>Manager</role> </Employee> <Employee id="4"> <age>25</age> <name>Meghna<New_Node1> <newnodeInside attrib="attrib_value">This is the content</newnodeInside> </New_Node1> </name> <gender>Female</gender> <role>Manager</role> </Employee> </Employees>
if needed to insert the node outside the name it’s necessary just to modify the XPATH query that will be
/Employees/Employee[gender='Female']/name
the project is available here
