How to Convert XML to Java Object - JAXB Unmarshalling

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Java XML Tutorial

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In this article, we will learn how to convert XML to Java object using Java Architecture for XML Binding (JAXB).

Java Architecture for XML Binding (JAXB) is a Java standard that defines how Java objects are converted from and to XML. It uses a standard set of mappings.

In JAXB term Converting XML to Java Object is called JAXB Unmarshalling. JAXB API provides the UnMarshaller interface, we can unmarshal(read) the object into an XML document.

Check out How to Convert Java Object to XML - JAXB Marshalling

Let's see the steps to convert XML document into Java object.

• Create POJO or bind the schema and generate the classes
• Create the JAXBContext object
• Create the Unmarshaller objects
• Call the unmarshal method
• Use getter methods of POJO to access the data

Unmarshaller example: Converting XML document into Java object

XML Document

Here is XML file that we are going to convert to Java Object:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:bookstore
 xmlns:ns2="net.javaguides.javaxmlparser.jaxb">
 <bookList>
  <book>
   <author>Joshua Bloch</author>
   <title>Effective Java</title>
   <publisher>Amazon</publisher>
   <isbn>978-0134685991</isbn>
  </book>
  <book>
   <author>Kathy Sierra</author>
   <title>Head First Java, 2nd Edition</title>
   <publisher>amazon</publisher>
   <isbn>978-0596009205</isbn>
  </book>
 </bookList>
 <location>Newyorkt</location>
 <name>Amazon Bookstore</name>
</ns2:bookstore>

Create POJO classes and Add JAXB annotations

Some basic and useful JAXB annotations are:

1. @XmlRootElement: This is a must-have an annotation for the Object to be used in JAXB. It defines the root element for the XML content.
2. @XmlType: It maps the class to the XML schema type. We can use it for ordering the elements in the XML.
3. @XmlTransient: This will make sure that the Object property is not written to the XML.
4. @XmlAttribute: This will create the Object property as an attribute.
5. @XmlElement(name = “ABC”): This will create the element with name “ABC”

Book POJO Class

package net.javaguides.javaxmlparser.jaxb;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlRootElement(name = "book")
@XmlType(propOrder = {
    "author",
    "name",
    "publisher",
    "isbn"
})
public class Book {

    private String name;
    private String author;
    private String publisher;
    private String isbn;

    @XmlElement(name = "title")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getPublisher() {
        return publisher;
    }

    public void setPublisher(String publisher) {
        this.publisher = publisher;
    }

    public String getIsbn() {
        return isbn;
    }

    public void setIsbn(String isbn) {
        this.isbn = isbn;
    }
}

Bootstore POJO Class

package net.javaguides.javaxmlparser.jaxb;

import java.util.List;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(namespace = "net.javaguides.javaxmlparser.jaxb")
public class Bookstore {

    @XmlElementWrapper(name = "bookList")
    @XmlElement(name = "book")
    private List < Book > bookList;
    private String name;
    private String location;

    public void setBookList(List < Book > bookList) {
        this.bookList = bookList;
    }

    public List < Book > getBooksList() {
        return bookList;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }
}

Unmarshaller Class - Convert XML to Object in Java

package net.javaguides.javaxmlparser.jaxb;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;

/**
 * Unmarshaller Class - Convert XML to Object in Java
 * @author Ramesh Fadatare
 *
 */
public class BookMain {
    private static final String BOOKSTORE_XML = "bookstore-jaxb.xml";

    public static void main(String[] args) throws JAXBException, IOException {

        List < Book > bookList = new ArrayList < Book > ();

        // create books
        Book book1 = new Book();
        book1.setIsbn("978-0134685991");
        book1.setName("Effective Java");
        book1.setAuthor("Joshua Bloch");
        book1.setPublisher("Amazon");
        bookList.add(book1);

        Book book2 = new Book();
        book2.setIsbn("978-0596009205");
        book2.setName("Head First Java, 2nd Edition");
        book2.setAuthor("Kathy Sierra");
        book2.setPublisher("amazon");
        bookList.add(book2);

        // create bookstore, assigning book
        Bookstore bookstore = new Bookstore();
        bookstore.setName("Amazon Bookstore");
        bookstore.setLocation("Newyorkt");
        bookstore.setBookList(bookList);

        convertXMLToObject();
    }

    private static Bookstore convertXMLToObject() {
        try {
            JAXBContext context = JAXBContext.newInstance(Bookstore.class);
            Unmarshaller un = context.createUnmarshaller();
            Bookstore bookstore = (Bookstore) un.unmarshal(new File(BOOKSTORE_XML));
            List < Book > list = bookstore.getBooksList();
            for (Book book: list) {
                System.out.println("Book: " + book.getName() + " from " + book.getAuthor());
            }
        } catch (JAXBException e) {
            e.printStackTrace();
        }
        return null;
    }
}

Output:

Book: Effective Java from Joshua Bloch
Book: Head First Java, 2nd Edition from Kathy Sierra

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Java XML Tutorial

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