Jaxb2实现JavaBean与xml互转的方法详解

2022-11-09 22:07:26

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]]]
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