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
* @author zhuc
* @create 2013-3-29 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 converyToJavaBean(String xml, Class 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;
/**
* @author zhuc
* @create 2013-3-29 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;
@XmlElement
private Date calendar;
@XmlAttribute
private 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()
*/
@Override
public 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;
/**
* @author zhuc
* @create 2013-3-29 下午2:50:00
*/
public class JaxbTest1 {
/**
* @throws JAXBException
*/
@Test
public void showMarshaller() {
Book book = new Book();
book.setId(100);
book.setAuthor("James");
book.setCalendar(new Date());
book.setPrice(23.45f); //默认是0.0
String str = JaxbUtil.convertToXml(book);
System.out.println(str);
}
/**
* @throws JAXBException
*/
@Test
public void showUnMarshaller() {
String str = "" +
"" +
" James " +
" 2013-03-29T09:25:56.004+08:00 " +
" 23.45 " +
" ";
Book book = JaxbUtil.converyToJavaBean(str, Book.class);
System.out.println(book);
}
}
输出结果分别为：
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;
/**
* @author zhuc
* @create 2013-3-29 下午2:51:44
*/
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "student")
@XmlType(propOrder = {})
public class Student {
@XmlAttribute
private Integer id;
@XmlElement
private 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()
*/
@Override
public 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;
/**
* @author zhuc
* @create 2013-3-29 下午2:51:52
*/
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder = { "name", "desc" })
public class Role {
@XmlElement
private String name;
@XmlElement
private 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()
*/
@Override
public String toString() {
return "Role [name=" + name + ", desc=" + desc + "]";
}
}
package t2;
import org.junit.Test;
import utils.JaxbUtil;
/**
* @author zhuc
* @create 2013-3-29 下午2:52:00
*/
public class JaxbTest2 {
@Test
public 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);
}
@Test
public void showUnMarshaller() {
String str = ""+
""+
" test "+
" "+
" 班长 "+
" 管理 "+
" "+
" ";
Student student = JaxbUtil.converyToJavaBean(str, Student.class);
System.out.println(student);
}
}
输出结果分别为：
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;
/**
* @author zhuc
* @create 2013-3-29 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 provinceList;
/**
* @return the name
*/
public String getName() {
return name;
}
/**
* @return the provinceList
*/
public List 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 provinceList) {
this.provinceList = provinceList;
}
/* (non-Javadoc)
* @see java.lang.Object#toString()
*/
@Override
public 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;
/**
* @author zhuc
* @create 2013-3-29 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()
*/
@Override
public 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;
/**
* @author zhuc
* @create 2013-3-29 下午2:56:11
*/
public class JaxbTest3 {
/**
* @throws JAXBException
*/
@Test
public void showMarshaller() {
Country country = new Country();
country.setName("中国");
List list = new ArrayList();
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);
}
/**
*
*/
@Test
public void showUnMarshaller() {
String str = ""+
""+
" 中国 "+
" "+
" "+
" 江苏省 "+
" 南京市 "+
" "+
" "+
" 浙江省 "+
" 杭州市 "+
" "+
" "+
" ";
Country country = JaxbUtil.converyToJavaBean(str, Country.class);
System.out.println(country);
}
}
输出结果分别为：
Country [name=中国, provinceList=[Province [name=江苏省, provCity=南京市], Province [name=浙江省, provCity=杭州市]]]