JAXB的使用（java对象和xml文本的相互转换）

JAXB（Java Architecture for XML Binding) 是一个业界的标准，是一项可以根据XML Schema产生Java类的技术。该过程中，JAXB也提供了将XML实例文档反向生成Java对象树的方法，并能将Java对象树的内容重新写到XML实例文档。从另一方面来讲，JAXB提供了快速而简便的方法将XML模式绑定到Java表示，从而使得Java开发者在Java应用程序中能方便地结合XML数据和处理函数， 在JDK1.6时，JAXB 2.0是JDK 1.6的组成部分。JAXB 2.2.3是JDK 1.7的组成部分。

JDK中JAXB相关的重要Class和Interface：

JAXBContext类，是应用的入口，用于管理XML/Java绑定信息。

Marshaller接口，将Java对象序列化为XML数据。

Unmarshaller接口，将XML数据反序列化为Java对象。

JDK中JAXB相关的重要Annotation：

@XmlType，将Java类或枚举类型映射到XML模式类型

@XmlAccessorType(XmlAccessType.FIELD) ，控制字段或属性的序列化。FIELD表示JAXB将自动绑定Java类中的每个非静态的（static）、非瞬态的（由@XmlTransient标注）字段到XML。其他值还有XmlAccessType.PROPERTY和XmlAccessType.NONE。

@XmlAccessorOrder，控制JAXB 绑定类中属性和字段的排序。

@XmlJavaTypeAdapter，使用定制的适配器（即扩展抽象类XmlAdapter并覆盖marshal()和unmarshal()方法），以序列化Java类为XML。

@XmlElementWrapper ，对于数组或集合（即包含多个元素的成员变量），生成一个包装该数组或集合的XML元素（称为包装器）。

@XmlRootElement，将Java类或枚举类型映射到XML元素。

@XmlElement，将Java类的一个属性映射到与属性同名的一个XML元素。

@XmlAttribute，将Java类的一个属性映射到与属性同名的一个XML属性。

实例

创建一个User类和一个Book类，其中User类含有一个Book类的集合属性

User类：

package com.yaolong.jax2xml.bean;

import java.io.Serializable;
import java.util.List;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "USER")
@XmlType(propOrder={"username","age","height","hobby","books"})
public class User implements Serializable{

private static final long serialVersionUID = 1L;

@XmlElement(name = "USERNAME")
private String username;

@XmlElement(name = "AGE")
private String age;

@XmlElement(name = "HEIGHT")
private String height;

@XmlElement(name = "HOBBY")
private String hobby;

@XmlElementWrapper(name = "BOOKS")
@XmlElement(name = "BOOK")
private List<Book> books;

public User() {

}

public User(String username, String age, String height, String hobby,List<Book> books) {
super();
this.username = username;
this.age = age;
this.height = height;
this.hobby = hobby;
this.books = books;
}

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public String getAge() {
return age;
}

public void setAge(String age) {
this.age = age;
}

public String getHeight() {
return height;
}

public void setHeight(String height) {
this.height = height;
}

public String getHobby() {
return hobby;
}

public void setHobby(String hobby) {
this.hobby = hobby;
}

public List<Book> getBooks() {
return books;
}

public void setBook(List<Book> books) {
this.books = books;
}

@Override
public String toString() {
return "User [username=" + username + ", age=" + age + ", height="
+ height + ", hobby=" + hobby + ", books=" + books + "]";
}

}

Book类：

package com.yaolong.jax2xml.bean;

import java.io.Serializable;

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

@XmlRootElement(name="BOOK")
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder={"bookName","price","desc"})
public class Book implements Serializable{

private static final long serialVersionUID = 1L;

@XmlElement(name="DESCRIPTION")
private String desc;

@XmlElement(name="BOOKNAME")
private String bookName;

@XmlElement(name="PRICE")
private String price;

public Book(){

}

public Book(String desc, String bookName, String price) {
super();
this.desc = desc;
this.bookName = bookName;
this.price = price;
}

public String getBookName() {
return bookName;
}

public void setBookName(String bookName) {
this.bookName = bookName;
}

public String getPrice() {
return price;
}

public void setPrice(String price) {
this.price = price;
}

public String getDesc() {
return desc;
}

public void setDesc(String desc) {
this.desc = desc;
}

@Override
public String toString() {
return "Book [desc=" + desc + ", bookName=" + bookName + ", price="
+ price + "]";
}

}

JaxB工具类：

package com.yaolong.jax2xml;

import java.io.StringReader;
import java.io.StringWriter;

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

/**
* @Description:xml和对象相互转换工具类
* @author:yaolong
* @data:2017年2月9日 下午10:46:57
* @version:1.0
*/
public class JaxbUtil {

/**
* JavaBean转换成xml 默认编码UTF-8
*
* @param obj
* @param writer
* @return
*/
public static String convertToXml(Object obj) {
return convertToXml(obj, "UTF-8");
}

/**
* JavaBean转换成xml
*
* @param obj
* @param encoding
* @return
*/
public static String convertToXml(Object obj, String encoding) {
String result = null;
try {
JAXBContext context = JAXBContext.newInstance(obj.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, false);// 是否省略xml头信息
StringWriter writer = new StringWriter();
marshaller.marshal(obj, writer);
result = writer.toString();
} catch (Exception e) {
e.printStackTrace();
}

return result;
}

/**
* xml转换成JavaBean
* @param xml
* @param c
* @return
* @throws JAXBException
*/
@SuppressWarnings("unchecked")
public static <T> T converyToJavaBean(String xml, Class<T> c)
throws JAXBException {
T t = null;
JAXBContext context = JAXBContext.newInstance(c);
Unmarshaller unmarshaller = context.createUnmarshaller();
t = (T) unmarshaller.unmarshal(new StringReader(xml));
return t;
}
}

测试类：

package com.yaolong.jax2xml;

import java.util.ArrayList;
import java.util.List;

import javax.xml.bind.JAXBException;

import com.yaolong.jax2xml.bean.Book;
import com.yaolong.jax2xml.bean.User;

public class JaxbeanTest {

public static void main(String[] args) throws JAXBException {
//准备数据
Book book1 = new Book("葵花宝典","100元","欲练此功，必须自宫");
Book book2 = new Book("辟邪剑谱","120元","不用自宫也能练");
Book book3 = new Book("九阴真经","130元","练完此功，天下无敌");
List<Book> books = new ArrayList<Book>();
books.add(book1);
books.add(book2);
books.add(book3);
User user = new User("吴渣渣","23","170","睡觉",books);
//将对象转化成xml文本
String xmlStr = JaxbUtil.convertToXml(user, "UTF-8");
System.out.println(xmlStr);

System.out.println("===================================================================================================");

//xml文本转换成对象
String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>"
+ "<USER>"
+ "<USERNAME>吴渣渣</USERNAME>"
+ "<AGE>23</AGE>"
+ "<HEIGHT>170</HEIGHT>"
+ "<HOBBY>睡觉</HOBBY>"
+ "<BOOKS>"
+ "<BOOK>"
+ "<BOOKNAME>100元</BOOKNAME>"
+ "<PRICE>欲练此功，必须自宫</PRICE>"
+ "<DESCRIPTION>葵花宝典</DESCRIPTION>"
+ "</BOOK>"
+ "<BOOK>"
+ "<BOOKNAME>120元</BOOKNAME>"
+ "<PRICE>不用自宫也能练</PRICE>"
+ "<DESCRIPTION>辟邪剑谱</DESCRIPTION>"
+ "</BOOK>"
+ "<BOOK>"
+ "<BOOKNAME>130元</BOOKNAME>"
+ "<PRICE>练完此功，天下无敌</PRICE>"
+ "<DESCRIPTION>九阴真经</DESCRIPTION>"
+ "</BOOK>"
+ "</BOOKS>"
+ "</USER>";

User userBean = JaxbUtil.converyToJavaBean(xml, User.class);
System.err.println(userBean);

}

}

打印结果：