Jaxb2中如何将avaBean转换为xml

Jaxb2中如何将avaBean转换为xml？针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。

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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 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 + "]";
  }
}

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\"?>" +
      "" +
      "  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：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

  James
  2013-03-29T14:50:58.974+08:00
  23.45

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\"?>"+
      ""+
      "  test"+
       "  "+
       "   班长"+
        "   管理"+
        ""+
      "";
    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"?>

  test
  
    班长
    管理
  

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 + "]";
  }
}

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 list = new ArrayList();
    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\"?>"+
      ""+
      "  中国"+
      "  "+
      "    "+
      "      江苏省"+
       "      南京市"+
      "    "+
       "    "+
       "      浙江省"+
       "      杭州市"+
       "    "+
      "  "+
      "";
    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"?>

  中国
  
    
      江苏省
      南京市
    
    
      浙江省
      杭州市
    
  

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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