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]]]