JAXB 编组示例：将对象转换为 XML

2024 年 8 月 29 日 | 阅读 2 分钟

通过 Marshaller 接口，我们可以将对象编组（写入）到 xml 文档中。在上一页中，我们已经看到了将对象转换为 xml 的简单示例。

在此示例中，我们将要把包含原始类型、字符串和集合对象的对象转换为 xml。

让我们看看将 java 对象转换为 XML 文档的步骤。

创建 POJO 或绑定模式并生成类
创建 JAXBContext 对象
创建 Marshaller 对象
通过使用 set 方法创建内容树
调用 marshal 方法

文件: 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;
}
}

文件: 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;
}

}

文件: 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"));
     
}
}

输出

生成的 xml 文件将如下所示

文件: 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>

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