JAXB--学习1
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> 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
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 = "<?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; /** * @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 = "<?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; /** * @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<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() */ @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<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); } /** * */ @Test public 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]]]
