Jaxb2 实现JavaBean与xml互转

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一、简介

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。

Jaxb 2.0是JDK 1.6的组成部分。我们不需要下载第三方jar包即可做到轻松转换。Jaxb2使用了JDK的新特性，如：Annotation、GenericType等，需要在即将转换的JavaBean中添加annotation注解。

二、重要概念

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。

@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。

三、示例

1、准备工作

package utils;import java.io.StringReader;import java.io.StringWriter;import javax.xml.bind.JAXBContext;import javax.xml.bind.Marshaller;import javax.xml.bind.Unmarshaller;/** * Jaxb2工具类 * @authorzhuc * @create2013-3-29 下午2:40:14 */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);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 */@SuppressWarnings("unchecked")public static <T> T converyToJavaBean(String xml, Class<T> c) {T t = null;try {JAXBContext context = JAXBContext.newInstance(c);Unmarshaller unmarshaller = context.createUnmarshaller();t = (T) unmarshaller.unmarshal(new StringReader(xml));} catch (Exception e) {e.printStackTrace();}return t;}}

非常简单易懂，需要注意的是

marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);

Marshaller.JAXB_FORMATTED_OUTPUT 决定是否在转换成xml时同时进行格式化（即按标签自动换行，否则即是一行的xml）

Marshaller.JAXB_ENCODING xml的编码方式

另外，Marshaller 还有其他Property可以设置，可以去查阅api。

2、最简单转换

package t1;import java.util.Date;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlAttribute;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlRootElement;import javax.xml.bind.annotation.XmlType;/** * @authorzhuc * @create2013-3-29 下午2:49:48 */@XmlAccessorType(XmlAccessType.FIELD)@XmlRootElement@XmlType(name = "book", propOrder = { "author", "calendar", "price", "id" })public class Book {@XmlElement(required = true)private String author;@XmlElement(name = "price_1", required = true)private float price;@XmlElementprivate Date calendar;@XmlAttributeprivate Integer id;/** * @return the author */public String getAuthor() {return author;}/** * @return the price */public float getPrice() {return price;}/** * @return the calendar */public Date getCalendar() {return calendar;}/** * @return the id */public Integer getId() {return id;}/** * @param author the author to set */public void setAuthor(String author) {this.author = author;}/** * @param price the price to set */public void setPrice(float price) {this.price = price;}/** * @param calendar the calendar to set */public void setCalendar(Date calendar) {this.calendar = calendar;}/** * @param id the id to set */public void setId(Integer id) {this.id = id;}/* (non-Javadoc) * @see java.lang.Object#toString() */@Overridepublic String toString() {return "Book [author=" + author + ", price=" + price + ", calendar=" + calendar + ", id=" + id + "]";}}

package t1;import java.util.Date;import javax.xml.bind.JAXBException;import org.junit.Test;import utils.JaxbUtil;/** * @authorzhuc * @create2013-3-29 下午2:50:00 */public class JaxbTest1 {/** * @throws JAXBException */@Testpublic void showMarshaller()  {Book book = new Book();book.setId(100);book.setAuthor("James");book.setCalendar(new Date());book.setPrice(23.45f); //默认是0.0String str = JaxbUtil.convertToXml(book);System.out.println(str);}/** * @throws JAXBException */@Testpublic void showUnMarshaller() {String str = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>" +"<book id=\"100\">" +"    <author>James</author>" + "   <calendar>2013-03-29T09:25:56.004+08:00</calendar>" +  "  <price_1>23.45</price_1>" +"</book>";Book book = JaxbUtil.converyToJavaBean(str, Book.class);System.out.println(book);}}

输出结果分别为：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<book id="100">
    <author>James</author>
    <calendar>2013-03-29T14:50:58.974+08:00</calendar>
    <price_1>23.45</price_1>
</book>

Book [author=James, price=23.45, calendar=Fri Mar 29 09:25:56 CST 2013, id=100]

3、类中包含复杂对象的转换

package t2;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlAttribute;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlRootElement;import javax.xml.bind.annotation.XmlType;/** * @authorzhuc * @create2013-3-29 下午2:51:44 */@XmlAccessorType(XmlAccessType.FIELD)@XmlRootElement(name = "student")@XmlType(propOrder = {})public class Student {@XmlAttributeprivate Integer id;@XmlElementprivate String name;@XmlElement(name = "role")private Role role;/** * @return the id */public Integer getId() {return id;}/** * @return the name */public String getName() {return name;}/** * @return the role */public Role getRole() {return role;}/** * @param id the id to set */public void setId(Integer id) {this.id = id;}/** * @param name the name to set */public void setName(String name) {this.name = name;}/** * @param role the role to set */public void setRole(Role role) {this.role = role;}/* (non-Javadoc) * @see java.lang.Object#toString() */@Overridepublic String toString() {return "Student [id=" + id + ", name=" + name + ", role=" + role + "]";}}

package t2;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlType;/** * @authorzhuc * @create2013-3-29 下午2:51:52 */@XmlAccessorType(XmlAccessType.FIELD)@XmlType(propOrder = { "name", "desc" })public class Role {@XmlElementprivate String name;@XmlElementprivate String desc;/** * @return the name */public String getName() {return name;}/** * @return the desc */public String getDesc() {return desc;}/** * @param name the name to set */public void setName(String name) {this.name = name;}/** * @param desc the desc to set */public void setDesc(String desc) {this.desc = desc;}/* (non-Javadoc) * @see java.lang.Object#toString() */@Overridepublic String toString() {return "Role [name=" + name + ", desc=" + desc + "]";}}

package t2;import org.junit.Test;import utils.JaxbUtil;/** * @authorzhuc * @create2013-3-29 下午2:52:00 */public class JaxbTest2 {@Testpublic void showMarshaller() {Student student = new Student();student.setId(12);student.setName("test");Role role = new Role();role.setDesc("管理");role.setName("班长");student.setRole(role);String str = JaxbUtil.convertToXml(student);System.out.println(str);}@Testpublic void showUnMarshaller() {String str = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>"+"<student id=\"12\">"+"    <name>test</name>"+ "   <role>"+  "      <name>班长</name>"+   "     <desc>管理</desc>"+    "</role>"+"</student>";Student student = JaxbUtil.converyToJavaBean(str, Student.class);System.out.println(student);}}

输出结果分别为：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<student id="12">
    <name>test</name>
    <role>
        <name>班长</name>
        <desc>管理</desc>
    </role>
</student>

Student [id=12, name=test, role=Role [name=班长, desc=管理]]

4、集合对象的转换（同样适用于Set）

package t3;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;/** * @authorzhuc * @create2013-3-29 下午2:55:56 */@XmlAccessorType(XmlAccessType.FIELD)@XmlRootElement(name = "country")@XmlType(propOrder = { "name", "provinceList" })public class Country {@XmlElement(name = "country_name")private String name;@XmlElementWrapper(name = "provinces")@XmlElement(name = "province")private List<Province> provinceList;/** * @return the name */public String getName() {return name;}/** * @return the provinceList */public List<Province> getProvinceList() {return provinceList;}/** * @param name the name to set */public void setName(String name) {this.name = name;}/** * @param provinceList the provinceList to set */public void setProvinceList(List<Province> provinceList) {this.provinceList = provinceList;}/* (non-Javadoc) * @see java.lang.Object#toString() */@Overridepublic String toString() {return "Country [name=" + name + ", provinceList=" + provinceList + "]";}}

package t3;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlType;/** * @authorzhuc * @create2013-3-29 下午2:56:03 */@XmlAccessorType(XmlAccessType.FIELD)@XmlType(propOrder = { "name", "provCity" })public class Province {@XmlElement(name = "province_name")private String name;@XmlElement(name = "prov_city")private String provCity;/** * @return the provCity */public String getProvCity() {return provCity;}/** * @param provCity the provCity to set */public void setProvCity(String provCity) {this.provCity = provCity;}/** * @return the name */public String getName() {return name;}/** * @param name the name to set */public void setName(String name) {this.name = name;}/* (non-Javadoc) * @see java.lang.Object#toString() */@Overridepublic String toString() {return "Province [name=" + name + ", provCity=" + provCity + "]";}}

package t3;import java.util.ArrayList;import java.util.List;import org.junit.Test;import utils.JaxbUtil;/** * @authorzhuc * @create2013-3-29 下午2:56:11 */public class JaxbTest3 {/** * @throws JAXBException */@Testpublic void showMarshaller() {Country country = new Country();country.setName("中国");List<Province> list = new ArrayList<Province>();Province province = new Province();province.setName("江苏省");province.setProvCity("南京市");Province province2 = new Province();province2.setName("浙江省");province2.setProvCity("杭州市");list.add(province);list.add(province2);country.setProvinceList(list);String str = JaxbUtil.convertToXml(country);System.out.println(str);}/** *  */@Testpublic void showUnMarshaller() {String str = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>"+"<country>"+"    <country_name>中国</country_name>"+"    <provinces>"+"        <province>"+"            <province_name>江苏省</province_name>"+ "           <prov_city>南京市</prov_city>"+"        </province>"+ "       <province>"+ "           <province_name>浙江省</province_name>"+ "           <prov_city>杭州市</prov_city>"+ "       </province>"+"    </provinces>"+"</country>";Country country = JaxbUtil.converyToJavaBean(str, Country.class);System.out.println(country);}}

输出结果分别为：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<country>
    <country_name>中国</country_name>
    <provinces>
        <province>
            <province_name>江苏省</province_name>
            <prov_city>南京市</prov_city>
        </province>
        <province>
            <province_name>浙江省</province_name>
            <prov_city>杭州市</prov_city>
        </province>
    </provinces>
</country>

Country [name=中国, provinceList=[Province [name=江苏省, provCity=南京市], Province [name=浙江省, provCity=杭州市]]]

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