Objective:
In the previous article Parsing an XML file using SAX we learned about parsing an XML file using SAX. In the article we will learn about How to convert an object into XML document and XML document into Object.
Converting Object to XML in Java:
By the help of Marshaller interface, we can marshal(write) the object into xml document. In the previous page, we have seen the simple example of converting object into xml.
In this example, we are going to convert the object into xml having primitives, strings and collection objects.
Let's see the steps to convert java object into XML document.
- Create POJO or bind the schema and generate the classes
- Create the JAXBContext object
- Create the Marshaller objects
- Create the content tree by using set methods
- Call the marshal method
File: Question.java
import java.util.List;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Question {
private int id;
private String questionname;
private List<Answer> answers;
public Question() {}
public Question(int id, String questionname, List<Answer> answers) {
super();
this.id = id;
this.questionname = questionname;
this.answers = answers;
}
@XmlAttribute
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@XmlElement
public String getQuestionname() {
return questionname;
}
public void setQuestionname(String questionname) {
this.questionname = questionname;
}
@XmlElement
public List<Answer> getAnswers() {
return answers;
}
public void setAnswers(List<Answer> answers) {
this.answers = answers;
}
}
File: Answer.java
public class Answer {
private int id;
private String answername;
private String postedby;
public Answer() {}
public Answer(int id, String answername, String postedby) {
super();
this.id = id;
this.answername = answername;
this.postedby = postedby;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getAnswername() {
return answername;
}
public void setAnswername(String answername) {
this.answername = answername;
}
public String getPostedby() {
return postedby;
}
public void setPostedby(String postedby) {
this.postedby = postedby;
}
}
File: ObjectToXml.java
import java.io.FileOutputStream;
import java.util.ArrayList;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
public class ObjectToXml {
public static void main(String[] args) throws Exception{
JAXBContext contextObj = JAXBContext.newInstance(Question.class);
Marshaller marshallerObj = contextObj.createMarshaller();
marshallerObj.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
Answer ans1=new Answer(101,"java is a programming language","ravi");
Answer ans2=new Answer(102,"java is a platform","john");
ArrayList<Answer> list=new ArrayList<Answer>();
list.add(ans1);
list.add(ans2);
Question que=new Question(1,"What is java?",list);
marshallerObj.marshal(que, new FileOutputStream("question.xml"));
}
}
//Output:
The generated XML file :
File: Question.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<question id="1">
<answers>
<answername>java is a programming language</answername>
<id>101</id>
<postedby>ravi</postedby>
</answers>
<answers>
<answername>java is a platform</answername>
<id>102</id>
postedby>john</postedby>
</answers>
<questionname>What is java?</questionname>
</question>
Converting XML into Object:
By the help of UnMarshaller interface, we can unmarshal(read) the object into xml document.
In this example, we are going to convert simple xml document into java object.
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
File: question.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<question id="1">
<answers>
<answername>java is a programming language</answername>
<id>101</id>
<postedby>ravi</postedby>
</answers>
<answers>
<answername>java is a platform</answername>
<id>102</id>
<postedby>john</postedby>
</answers>
<questionname>What is java?</questionname>
</question>
POJO classes
File: Question.java
import java.util.List;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Question {
private int id;
private String questionname;
private List<Answer> answers;
public Question() {}
public Question(int id, String questionname, List<Answer> answers) {
super();
this.id = id;
this.questionname = questionname;
this.answers = answers;
}
@XmlAttribute
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@XmlElement
public String getQuestionname() {
return questionname;
}
public void setQuestionname(String questionname) {
this.questionname = questionname;
}
@XmlElement
public List<Answer> getAnswers() {
return answers;
}
public void setAnswers(List<Answer> answers) {
this.answers = answers;
}
}
File: Answer.java
public class Answer {
private int id;
private String answername;
private String postedby;
public Answer() {}
public Answer(int id, String answername, String postedby) {
super();
this.id = id;
this.answername = answername;
this.postedby = postedby;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getAnswername() {
return answername;
}
public void setAnswername(String answername) {
this.answername = answername;
}
public String getPostedby() {
return postedby;
}
public void setPostedby(String postedby) {
this.postedby = postedby;
}
}
Unmarshaller class
File: XmlToObject.javaimport java.io.File;
import java.util.List;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
public class XmlToObject {
public static void main(String[] args) {
try {
File file = new File("question.xml");
JAXBContext jaxbContext = JAXBContext.newInstance(Question.class);
Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
Question que= (Question) jaxbUnmarshaller.unmarshal(file);
System.out.println(que.getId()+" "+que.getQuestionname());
System.out.println("Answers:");
List<Answer> list=que.getAnswers();
for(Answer ans:list)
System.out.println(ans.getId()+" "+ans.getAnswername()+" "+ans.getPostedby());
} catch (JAXBException e) {
e.printStackTrace();
}
}
}
//Output:
1 What is java?
Answers:
101 java is a programming language ravi
102 java is a platform john
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