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]]]