Jaxb2 转换XML文档

Jaxb2 转换XML文档

介绍
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。

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。

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 + "]";
       }
   
   }

   Java代码:

   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 id="100">
       <author>Jamesauthor>
       <calendar>2013-03-29T14:50:58.974+08:00calendar>
       <price_1>23.45price_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 = ""+
               ""+
               "    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>testname>
       <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 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 + "]";
       }
   
   }
   

   输出:

   
   <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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