JAXB的使用（java对象和xml文本的相互转换）

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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：

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