JAXB（Java Architecture for XML Binding) 詳解及實例分析

一、簡介

JAXB（Java Architecture for XML Binding) 是一個業界的標準，是一項可以根據XML Schema產生Java類的技術。該過程中，JAXB也提供了將XML實例文檔反向生成Java對象樹的方法，並能將Java對象樹的內容重新寫到 XML實例文檔。

Jaxb 2.0是JDK 1.6的組成部分。我們不需要下載第三方jar包即可做到輕鬆轉換。Jaxb2使用了JDK的新特性，如：Annotation、GenericType等，需要在即將轉換的JavaBean中添加annotation註解。

二、重要概念

JAXBContext類，是應用的入口，用於管理XML/Java綁定信息。

Marshaller接口，將Java對象序列化爲XML數據。

Unmarshaller接口，將XML數據反序列化爲Java對象。

@XmlType，將Java類或枚舉類型映射到XML模式類型

@XmlAccessorType(XmlAccessType.FIELD) ，控制字段或屬性的序列化。FIELD表示JAXB將自動綁定Java類中的每個非靜態的（static）、非瞬態的（由@XmlTransient標 注）字段到XML。其他值還有XmlAccessType.PROPERTY和XmlAccessType.NONE。

@XmlAccessorOrder，控制JAXB 綁定類中屬性和字段的排序。

@XmlJavaTypeAdapter，使用定製的適配器（即擴展抽象類XmlAdapter並覆蓋marshal()和unmarshal()方法），以序列化Java類爲XML。

@XmlElementWrapper ，對於數組或集合（即包含多個元素的成員變量），生成一個包裝該數組或集合的XML元素（稱爲包裝器）。

@XmlRootElement，將Java類或枚舉類型映射到XML元素。

@XmlElement，將Java類的一個屬性映射到與屬性同名的一個XML元素。

@XmlAttribute，將Java類的一個屬性映射到與屬性同名的一個XML屬性。

三、示例

1、準備工作

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工具類
 * @author   zhuc
 * @create   2013-3-29 下午2:40:14
 */
public class JaxbUtil {
  /**
   * JavaBean轉換成xml
   * 默認編碼UTF-8
   * @param obj
   * @param writer
   * @return
   */
  public static String convertToXml(Object obj) {
    return convertToXml(obj, "UTF-8");
  }
  /**
   * JavaBean轉換成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轉換成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;
  }
}

常簡單易懂，需要注意的是

marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);

Marshaller.JAXB_FORMATTED_OUTPUT 決定是否在轉換成xml時同時進行格式化（即按標籤自動換行，否則即是一行的xml）

Marshaller.JAXB_ENCODING xml的編碼方式

另外，Marshaller 還有其他Property可以設置，可以去查閱api。

2、最簡單轉換

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);  //默認是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);
  }
}

輸出結果分別爲：

<?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、類中包含複雜對象的轉換

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("班長");
    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>班長</name>"+
        "   <desc>管理</desc>"+
        "</role>"+
      "</student>";
    Student student = JaxbUtil.converyToJavaBean(str, Student.class);
    System.out.println(student);
  }
}

輸出結果分別爲：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<student id="12">
  <name>test</name>
  <role>
    <name>班長</name>
    <desc>管理</desc>
  </role>
</student>

Student [id=12, name=test, role=Role [name=班長, desc=管理]]

4、集合對象的轉換（同樣適用於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("中國");
    List<Province> list = new ArrayList<Province>();
    Province province = new Province();
    province.setName("江蘇省");
    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>中國</country_name>"+
      "  <provinces>"+
      "    <province>"+
      "      <province_name>江蘇省</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);
  }
}

輸出結果分別爲：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<country>
  <country_name>中國</country_name>
  <provinces>
    <province>
      <province_name>江蘇省</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=中國, provinceList=[Province [name=江蘇省, provCity=南京市], Province [name=浙江省, provCity=杭州市]]]

PS：這裏再爲大家推薦一款本站相關的JavaBean在線工具供大家參考使用：

在線JSON轉Java Bean代碼工具：
http://tools.jb51.net/code/json2javabean

JAXB（Java Architecture for XML Binding) 詳解及實例分析

一、簡介

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