JAXB解组示例：将XML转换为对象

借助UnMarshaller界面, 我们可以将对象解组（读取）为xml文档。

在此示例中, 我们将把简单的xml文档转换为java对象。

让我们看看将XML文档转换为Java对象的步骤。

• 创建POJO或绑定模式并生成类
• 创建JAXBContext对象
• 创建Unmarshaller对象
• 调用解组方法
• 使用POJO的getter方法访问数据

Unmarshaller示例：将xml文档转换为Java对象

Xml文件

<?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课程

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;
}
}

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;
}

}

编组课

import 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();
	  }
 
	}
}

输出：

1 What is java?
Answers:
101 java is a programming language ravi
102 java is a platform john