Jaxb2实现JavaBean与xml互转的方法详解

2024-07-13 10:06:19

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本文实例讲述了Jaxb2实现JavaBean与xml互转的方法。分享给大家供大家参考，具体如下：

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

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 = "<?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]]]

希望本文所述对大家java程序设计有所帮助。

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