Deserialization – How to convert XML to Java Objects using Jackson API

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The previous tutorials have explained the conversion of Java Objects to XML using Jackson API. This tutorial explains parsing the XML document to Java objects using Jackson API.

To parse the XML, we will use the Jackson library. Use the latest Jackson library.

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
    <version>2.13.0</version>
</dependency>

Jackson allows us to read the contents of an XML file and deserialize the XML back into a Java object. In our example, we will read an XML document containing details about an Employee, and use Jackson to extract this data and use it to create Java objects containing the same information.

First, let us create an XML document matching our class to read from. Create to_deserialize.xml with the following contents:

<Employee>
  <firstName>Vibha</firstName>
  <lastName>Singh</lastName>
  <age>30</age>
  <salary>75000.0</salary>
  <designation>Manager</designation>
  <contactNumber>+919999988822</contactNumber>
  <emailId>abc@test.com</emailId>
  <gender>female</gender>
  <maritalStatus>married</maritalStatus>
</Employee>

Deserialization – It is the reverse of serializing. In this process, we will read the Serialized byte stream from the file and convert it back into the Class instance representation. Here, we are converting a XML to an Employee class object.

Let us add a deserializeFromXML() function to deserialize the XML file above into a Java object:

	@Test
	public void deserializeFromXML() {

		XmlMapper xmlMapper = new XmlMapper();
		String userDir = System.getProperty("user.dir");

		// Converting Employee XML to Employee class object
		try {
			Employee emp = xmlMapper.readValue(new File(userDir + "\\src\\test\\resources\\XMLExample.xml"),
					Employee.class);
			System.out.println("Deserialized data: ");
			System.out.println("First Name of employee : " + emp.getFirstName());
			System.out.println("Last Name of employee : " + emp.getLastName());
			System.out.println("Age of employee : " + emp.getAge());
			System.out.println("Salary of employee : " + emp.getSalary());
			System.out.println("Designation of employee : " + emp.getDesignation());
			System.out.println("Contact Number of employee : " + emp.getContactNumber());
			System.out.println("EmailId of employee : " + emp.getEmailId());
			System.out.println("Marital Status of employee : " + emp.getMaritalStatus());
			System.out.println("Gender of employee : " + emp.getGender());

		} catch (StreamReadException e) {
			e.printStackTrace();
		} catch (DatabindException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

Manipulating Nested Elements in XML

Let us enhance our XML file to add nested elements and loops and modify our code to deserialize the following updated structure.

<Employees>
  <name>
    <firtsname>John</firtsname>
    <middlename>Dave</middlename>
    <lastname>William</lastname>
  </name>
  <contactdetails>
    <deskNumber>00-428507</deskNumber>
    <mobileNumber>+917823561231</mobileNumber>
    <emergencyDetails>
      <emergency_no1>+91 1212898920</emergency_no1>
      <emergency_no2>+91 9997722123</emergency_no2>
      <emergency_no3>+91 8023881245</emergency_no3>
    </emergencyDetails>
  </contactdetails>
  <age>30</age>
  <salary>75000.0</salary>
  <designation>Manager</designation>
  <emailId>abc@test.com</emailId>
  <gender>female</gender>
  <maritalStatus>married</maritalStatus>
</Employees>

There will be a slight change for the method deserializeFromXML() for the nested XML Structure.

   @Test
	public void deserializeFromXML() {

		XmlMapper xmlMapper = new XmlMapper();

		String userDir = System.getProperty("user.dir");

		// Converting Employee XML to Employee class object
		try {
			Employees employee2 = xmlMapper
					.readValue(new File(userDir + "\\src\\test\\resources\\NestedXMLExample.xml"), Employees.class);
			System.out.println("Deserialized data: ");
			System.out.println("First Name of employee : " + employee2.getName().getFirtsname());
			System.out.println("Middle Name of employee : " + employee2.getName().getMiddlename());
			System.out.println("Last Name of employee : " + employee2.getName().getLastname());
			System.out.println("Age of employee : " + employee2.getAge());
			System.out.println("Salary of employee : " + employee2.getSalary());
			System.out.println("Designation of employee : " + employee2.getDesignation());
			System.out.println("Desk Number of employee : " + employee2.getContactdetails().getDeskNumber());
			System.out.println("Mobile Number of employee : " + employee2.getContactdetails().getMobileNumber());
			System.out.println("Emergency Number1 of employee : "
					+ employee2.getContactdetails().getEmergencyDetails().getEmergency_no1());
			System.out.println("Emergency Number2 of employee : "
					+ employee2.getContactdetails().getEmergencyDetails().getEmergency_no2());
			System.out.println("Emergency Number3 of employee : "
					+ employee2.getContactdetails().getEmergencyDetails().getEmergency_no3());
			System.out.println("EmailId of employee : " + employee2.getEmailId());
			System.out.println("Gender of employee : " + employee2.getGender());
			System.out.println("Marital Status of employee : " + employee2.getMaritalStatus());

		} catch (StreamReadException e) {
			e.printStackTrace();
		} catch (DatabindException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

Here, you can see that when we need to serialize the nested attributes like Firstname, we have called the first Name class and then getFirstName().

System.out.println("First Name of employee : " + employee2.getName().getFirtsname());

To know about Serialization – Conversion of Java Objects to XML, you can refer to this tutorial.

We are done! Congratulations on making it through this tutorial and hope you found it useful! Happy Learning!!

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