Java对象的XML序列化和反序列化 - (1)

XML是一种标准的数据交换规范，可以方便地用于在应用之间交换各类数据。如果能在Java对象和XML文档之间建立某种映射，例如Java对象的XML序列化和反序列化，那么就可以使Java的对象方便地与其他应用进行交换。

java.beans包里面有两个类XMLEncoder和Decoder，分别用于将符合JabaBeans规范的Java对象以XML方式序列化和反序列化。以下代码显示了如何使用这两个类实现Java对象的XML编码和解码。

待序列化的Java类：

import java.io.Serializable;public class SerialableObject implements Serializable{   private static final long serialVersionUID = 8745578444312339136L;   public SerialableObject()   {   }   public SerialableObject(int id, String name, double value)   {      this.id = id;      this.name = name;      this.value = value;   }   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 double getValue()   {      return value;   }   public void setValue(double value)   {      this.value = value;   }   private int id;   private String name;   private double value;}

XML序列化和反序列化用法演示类：

import java.beans.XMLDecoder;import java.beans.XMLEncoder;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.util.List;import java.util.Vector;public class XmlSerialize{   public XmlSerialize()   {   }   public void serializeSingleObject(OutputStream os, Object obj)       // 序列化单个java对象   {      // XMLEncoder xe = new XMLEncoder(os);      XMLEncoder xe = new XMLEncoder(os, "GBK", true, 0);     // 仅用于Java SE 7      xe.writeObject(obj);    // 序列化成XML字符串      xe.close();   }   public Object deserializeSingleObject(InputStream is)       // 反序列化单个Java对象   {      XMLDecoder xd = new XMLDecoder(is);      Object obj = xd.readObject();       // 从XML序列中解码为Java对象      xd.close();      return obj;   }   public void serializeMultipleObject(OutputStream os, List<Object> objs)       // 序列化多个Java对象   {      XMLEncoder xe = new XMLEncoder(os);      xe.writeObject(objs);    // 序列化成XML字符串      xe.close();   }   public List<Object> deserializeMultipleObject(InputStream is)        // 反序列化多个Java对象   {      XMLDecoder xd = new XMLDecoder(is);      @SuppressWarnings("unchecked")      List<Object> objs = (List<Object>)xd.readObject();       // 从XML序列中解码为Java对象列表      xd.close();      return objs;   }   public void runSingleObject()   {      File xmlFile = new File("object.xml");      SerialableObject jo4Out = new SerialableObject(1, "Java序列化为XML", 3.14159265359);     // 创建待序列化的对象      try      {         FileOutputStream ofs = new FileOutputStream(xmlFile);       // 创建文件输出流对象         serializeSingleObject(ofs, jo4Out);         ofs.close();      } catch (FileNotFoundException e)      {         e.printStackTrace();      } catch (IOException e)      {         e.printStackTrace();      }      try      {         FileInputStream ifs = new FileInputStream(xmlFile);         SerialableObject jo4In = (SerialableObject)deserializeSingleObject(ifs);         System.out.println("id: " + jo4In.getId());         System.out.println("name: " + jo4In.getName());         System.out.println("value: " + jo4In.getValue());      } catch (FileNotFoundException e)      {         e.printStackTrace();      }   }   public void runMultipleObject()   {      File xmlFile = new File("objects.xml");      List<SerialableObject> sos4Out = new Vector<SerialableObject>();      sos4Out.add(new SerialableObject(1, "Java序列化为XML - 1", 3.14));     // 创建待序列化的对象      sos4Out.add(new SerialableObject(2, "Java序列化为XML - 2", 3.14159));     // 创建待序列化的对象      sos4Out.add(new SerialableObject(3, "Java序列化为XML - 3", 3.1415926));     // 创建待序列化的对象      sos4Out.add(new SerialableObject(4, "Java序列化为XML - 4", 3.141592653));     // 创建待序列化的对象      sos4Out.add(new SerialableObject(5, "Java序列化为XML - 5", 3.14159265359));     // 创建待序列化的对象      try      {         FileOutputStream ofs = new FileOutputStream(xmlFile);       // 创建文件输出流对象         serializeSingleObject(ofs, sos4Out);         ofs.close();      } catch (FileNotFoundException e)      {         e.printStackTrace();      } catch (IOException e)      {         e.printStackTrace();      }      try      {         FileInputStream ifs = new FileInputStream(xmlFile);         @SuppressWarnings("unchecked")         List<SerialableObject> sos4In = (List<SerialableObject>)deserializeSingleObject(ifs);         for(SerialableObject jo4In : sos4In)         {            System.out.println("id: " + jo4In.getId());            System.out.println("name: " + jo4In.getName());            System.out.println("value: " + jo4In.getValue());         }      } catch (FileNotFoundException e)      {         e.printStackTrace();      }   }   public static void main(String[] args)   {      XmlSerialize xs = new XmlSerialize();      xs.runSingleObject();      xs.runMultipleObject();   }}

需要注意的是，待序列化的类必须要符合JavaBeans的格式规范，即：具有一个无参的public构造函数，所有数据成员的访问均采用getter/setter模式，此外，这个类必须是public的，并且实现了java.io.Serializable接口。

程序运行之后，会产生两个文件：

object.xml是runSingleObject方法生成的，存放了单个的SerialableObject的值：

<?xml version="1.0" encoding="GBK"?><java version="1.7.0" class="java.beans.XMLDecoder"> <object class="SerialableObject">  <void property="id">   <int>1</int>  </void>  <void property="name">   <string>Java序列化为XML</string>  </void>  <void property="value">   <double>3.14159265359</double>  </void> </object></java> 

objects.xml是runMultipleObject方法产生的，存放了5个SerializableObject的值：

<?xml version="1.0" encoding="GBK"?><java version="1.7.0" class="java.beans.XMLDecoder"> <object class="java.util.Vector">  <void method="add">   <object class="SerialableObject">    <void property="id">     <int>1</int>    </void>    <void property="name">     <string>Java序列化为XML - 1</string>    </void>    <void property="value">     <double>3.14</double>    </void>   </object>  </void>  <void method="add">   <object class="SerialableObject">    <void property="id">     <int>2</int>    </void>    <void property="name">     <string>Java序列化为XML - 2</string>    </void>    <void property="value">     <double>3.14159</double>    </void>   </object>  </void>  <void method="add">   <object class="SerialableObject">    <void property="id">     <int>3</int>    </void>    <void property="name">     <string>Java序列化为XML - 3</string>    </void>    <void property="value">     <double>3.1415926</double>    </void>   </object>  </void>  <void method="add">   <object class="SerialableObject">    <void property="id">     <int>4</int>    </void>    <void property="name">     <string>Java序列化为XML - 4</string>    </void>    <void property="value">     <double>3.141592653</double>    </void>   </object>  </void>  <void method="add">   <object class="SerialableObject">    <void property="id">     <int>5</int>    </void>    <void property="name">     <string>Java序列化为XML - 5</string>    </void>    <void property="value">     <double>3.14159265359</double>    </void>   </object>  </void> </object></java>