java利用JAXB实现对象和xml互相转换方法与实例详解

1、JAXB应用场景

在使用WebService实现数据上传下载，数据查询时，可以利用JAXB实现java实体类和xml互相转换

2、Demo

2.1 student.java 实体类

包含list（set同理）、map、Teacher、Date 类型的属性

package jaxb;
import java.util.Date;
import java.util.List;
import java.util.Map;
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;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
@XmlType(propOrder={"id","name","age","birthDay","list","teacher","map"}) //指定序列成的xml节点顺序
@XmlAccessorType(value=XmlAccessType.FIELD) //访问类型改为字段
@XmlRootElement
public class Student {
   @XmlElement
   private String id;
   @XmlElement
   private String name;
   @XmlElement
   private int age;
   @XmlJavaTypeAdapter(value=DateAdapter.class)
   @XmlElement
   private Date birthDay;
   @XmlElement
   private List<Teacher> list;
   @XmlElement
   private Teacher teacher;

   @XmlJavaTypeAdapter(value=MapAdapter.class)
  // @XmlElementWrapper(name="role")
   @XmlElement
   private Map map;
  public String getId() {
    return id;
  }

  public void setId(String id) {
    this.id = id;
  }
  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
  public int getAge() {
    return age;
  }

  public void setAge(int age) {
    this.age = age;
  }
  public Date getBirthDay() {
    return birthDay;
  }

  public void setBirthDay(Date birthDay) {
    this.birthDay = birthDay;
  }

  public List getList() {
    return list;
  }

  public void setList(List list) {
    this.list = list;
  }
 public Teacher getTeacher() {
  return teacher;
 }
  public void setTeacher(Teacher teacher) {
  this.teacher = teacher;
  }

 public Map getMap() {
  return map;
 }

 public void setMap(Map map) {
  this.map = map;
 }

@Override
public String toString() {
  return "Student [id=" + id + ", name=" + name + ", age=" + age
      + ", birthDay=" + birthDay + ", list=" + list + ", teacher="
      + teacher + ", map=" + map + "]";
}

}

2.2 Teacher.java类 

注意:Teacher 类不包含@XmlRootElement节点，因为目的是转成一个XML文档，根节点只有一个

package jaxb;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(value=XmlAccessType.FIELD)
@XmlType(propOrder={"id","name","age"})
public class Teacher {
 @XmlElement
 private int id;
 @XmlElement
 private String name;
 @XmlElement
 private int age;
public int getId() {
  return id;
}
public void setId(int id) {
  this.id = id;
}
public String getName() {
  return name;
}
public void setName(String name) {
  this.name = name;
}
public int getAge() {
  return age;
}
public void setAge(int age) {
  this.age = age;
}
public Teacher(int id, String name, int age) {
  super();
  this.id = id;
  this.name = name;
  this.age = age;
}
public Teacher() {
}
@Override
public String toString() {
  return "Teacher [id=" + id + ", name=" + name + ", age=" + age + "]";
}

}

2.3 DateApdapter.java

自定义时间适配器类

在java实体类序列化xml日期时，需要对时间进行自定义转换，jaxb提供了XmlAdapter,只要实现它后就可以自定义日期适配器

package jaxb;

import java.text.SimpleDateFormat;
import java.util.Date;

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class DateAdapter extends XmlAdapter<String, Date> {
  //反序列化成日期对象Date
  @Override
  public Date unmarshal(String str) throws Exception {
    SimpleDateFormat format = getSimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    return str==null ? null:format.parse(str);
  }
  //序列化成xmL
  @Override
  public String marshal(Date date) throws Exception {
    SimpleDateFormat format = getSimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    return date==null ? "":format.format(date);
  }
  private SimpleDateFormat getSimpleDateFormat(String pattern){
    SimpleDateFormat format = new SimpleDateFormat(pattern);
    return format;
  }
}

2.4 Entry.java类 

用来封装map元素

package jaxb;

public class Entry {
 private String key;
 private Object value;
 public String getKey() {
  return key;
 }
 public void setKey(String key) {
  this.key = key;
 }
  public Object getValue() {
  return value;
 }
 public void setValue(Object value) {
  this.value = value;
 }

}

2.5、MapAdpter.java

map 转换器

本人在写map转换器之后，感觉跟jaxb 默认序列化的方式没什么区别，目前还不知道在javb中需不需要特地写map转换器，希望有经验的朋友分享下

package jaxb;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class MapAdapter extends XmlAdapter<MapAdapter.AdapterMap,Map<String,Object>> {

  public static class AdapterMap {
    public List<Entry> entry =new ArrayList<Entry>();
  }
  /**
   * 功能:xml->Map<String,Object>
   * @param adapterMap
   * @return
   * @throws Exception
   */
  @Override
  public Map<String, Object> unmarshal(AdapterMap adapterMap) throws Exception {
    Map<String, Object> map = new HashMap<String, Object>();
    List entry = adapterMap.entry;
    for(Entry en:adapterMap.entry){
      map.put(en.getKey(), en.getValue());
    }
    return map;
  }
  /**
   * 功能:map<String,Object> -> xml
   */
  @Override
  public AdapterMap marshal(Map<String, Object> map) throws Exception {
    AdapterMap adapterMap = new AdapterMap();
    for (Map.Entry<String, Object> entry : map.entrySet()) {
      Entry entry2 = new Entry();
      entry2.setKey(entry.getKey());
      entry2.setValue(entry.getValue());
      adapterMap.entry.add(entry2);
    }
    return adapterMap;
  }

}

 2.6 测试类 JaxbDemo.java

package jaxb;

import java.io.StringReader;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

public class JaxbDemo {

  public static void main(String[] args) {
    Student stu = new Student();
    stu.setId("1");
    stu.setName("罗志茂");
    stu.setAge(25);
    stu.setBirthDay(new Date());
    //list集合，set集合一样
    ArrayList<Teacher> list = new ArrayList<Teacher>();
    list.add(new Teacher(2,"曾利梅",22));
    list.add(new Teacher(3,"黄伙林",22));
    list.add(new Teacher(4,"潘志华",22));
    stu.setList(list);
    //在javaBean中添加javaBean
    Teacher teacher = new Teacher(1,"宋瑶",22);
    stu.setTeacher(teacher);
    //添加map集合
    HashMap<Object, Object> map = new HashMap<>();
    map.put("1", "林乐贤");
    map.put("2", "德甲");
    stu.setMap(map);
    try {
    JAXBContext context = JAXBContext.newInstance(Student.class);
    Marshaller marshaller = context.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
    marshaller.setProperty(Marshaller.JAXB_ENCODING, "GBK");
    //marshaller.marshal(stu, System.out);
    StringWriter writer = new StringWriter();
    marshaller.marshal(stu, writer);
    System.out.println(writer.toString());
    //反序列化
    Unmarshaller unmarshaller = context.createUnmarshaller();
    StringReader reader = new StringReader(writer.toString());
    Student stu2 = (Student) unmarshaller.unmarshal(reader);
    System.out.println("stu2"+stu2);
  } catch (JAXBException e) {
    e.getMessage();
    e.printStackTrace();
  }
  }
}

3.测试结果

<?xml version="1.0" encoding="GBK" standalone="yes"?>
<student>
  <id>1</id>
  <name>罗志茂</name>
  <age>25</age>
  <birthDay>2016-08-18 23:07:26</birthDay>
  <list>
    <id>2</id>
    <name>曾利梅</name>
    <age>22</age>
  </list>
  <list>
    <id>3</id>
    <name>黄伙林</name>
    <age>22</age>
  </list>
  <list>
    <id>4</id>
    <name>潘志华</name>
    <age>22</age>
  </list>
  <teacher>
    <id>1</id>
    <name>宋瑶</name>
    <age>22</age>
  </teacher>
  <map>
    <entry>
      <key>2</key>
      <value xsi:type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">德甲</value>
    </entry>
    <entry>
      <key>1</key>
      <value xsi:type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">林乐贤</value>
    </entry>
  </map>
</student>

stu2Student [id=1, name=罗志茂, age=25, birthDay=Thu Aug 18 23:07:26 CST 2016, list=[Teacher [id=2, name=曾利梅, age=22], Teacher [id=3, name=黄伙林, age=22], Teacher [id=4, name=潘志华, age=22]], teacher=Teacher [id=1, name=宋瑶, age=22], map={2=德甲, 1=林乐贤}]

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