Unmarshalling is the process of converting xml into java object. The unmarshal() method of JAXB Unmarshaller is used for unmarshalling process.
Steps:
1. Create a pojo class.
2. create JAXB context instance.
3. Create Unmarshaller instance using JAXB context.
4. Call unmarshal() method for unmarshalling process.
5. Process the pojo object.
Example explanation:
Below example have two pojo classes Student and Subject. A Student can have one or more Subject. Pass Student.xml file (generated from previous example) as a parameter in unmarshal() method and cast the return object to Student. Now we have Student object and can process it.
Example:
Student.java
import java.util.List;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlTransient;
/**
* This class represents a Student.
* @author javawithease
*/
@XmlRootElement
public class Student {
private String name;
private String rollNo;
private String className;
private int age;
private int id;
private List<Subject> subject;
//Default constructor
public Student(){
}
//Parameterised constructor
public Student(String name, String rollNo,
String className, int age,
int id, List<Subject> subject){
this.name = name;
this.rollNo = rollNo;
this.className = className;
this.age = age;
this.id = id;
this.subject = subject;
}
public String getName() {
return name;
}
@XmlElement
public void setName(String name) {
this.name = name;
}
public String getClassName() {
return className;
}
@XmlElement
public void setClassName(String className) {
this.className = className;
}
public String getRollNo() {
return rollNo;
}
@XmlElement
public void setRollNo(String rollNo) {
this.rollNo = rollNo;
}
public int getAge() {
return age;
}
@XmlTransient
public void setAge(int age) {
this.age = age;
}
public int getId() {
return id;
}
@XmlAttribute
public void setId(int id) {
this.id = id;
}
public List<Subject> getSubject() {
return subject;
}
@XmlElement
public void setSubject(List<Subject> subject) {
this.subject = subject;
}
} |
Subject.java
/**
* This class represents Address.
* @author javawithease
*/
public class Subject {
private String subjectname;
private String subjectId;
//Default constructor
public Subject(){
}
//Parameterised constructor
public Subject(String subjectname, String subjectId){
this.subjectname = subjectname;
this.subjectId = subjectId;
}
public String getSubjectname() {
return subjectname;
}
public void setSubjectname(String subjectname) {
this.subjectname = subjectname;
}
public String getSubjectId() {
return subjectId;
}
public void setSubjectId(String subjectId) {
this.subjectId = subjectId;
}
} |
JAXBTest.java
import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
/**
* This is test class for Unmarshalling.
* @author javawithease
*/
public class JAXBTest {
public static void main(String args[]){
try {
//create JAXB context
JAXBContext context = JAXBContext.newInstance(Student.class);
//Create Unmarshaller using JAXB context
Unmarshaller unmarshaller = context.createUnmarshaller();
Student student = (Student)
unmarshaller.unmarshal(new File("D:\\Student.xml"));
//Process the Student object
System.out.println("Student name: " + student.getName());
System.out.println("Student rollNo: " + student.getRollNo());
for(Subject Subject: student.getSubject()){
System.out.println("Subject Name: "
+ Subject.getSubjectname());
System.out.println("Subject Id: "
+ Subject.getSubjectId());
}
} catch (Exception e) {
e.printStackTrace();
}
}
} |
Output:
Student name: jai
Student rollNo: MCA/07/06
Subject Name: Java
Subject Id: 1
Subject Name: Oracle
Subject Id: 2 |
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