Simple-XML - 如何序列化集合中的派生類？

我想序列化一個對象層次結構，包括從基類「Thing」派生的對象列表。這工作得很好，包括反序列化 - 但以書面指定實際使用的Java類Simple-XML - 如何序列化集合中的派生類？

當我創建與下面的Java代碼的XML文件中的屬性XML的簡單堅持，內容是這樣的：

<example1> 
     <things> 
      <fruit class="com.mumpitz.simplexmltest.Apple" id="17"> 
      <sugar>212</sugar> 
      </fruit> 
      <fruit class="com.mumpitz.simplexmltest.Orange" id="25" weight="11.2"/> 
     </things> 
    </example1>

但這不是我想要的。我想有

<example1> 
     <things> 
      <apple id="17"> 
      <sugar>212</sugar> 
      </apple> 
      <orange id="25" weight="11.2"/> 
     </things> 
    </example1>

「蘋果」和不帶類屬性「橙色」的元素，而不是「果」以這樣的屬性。這可能嗎？

（第二個XML規定的現有模式;增加額外的屬性不是一個選項）

下面的代碼：

package com.mumpitz.simplexmltest; 

    import java.io.File; 
    import java.util.ArrayList; 

    import org.simpleframework.xml.Attribute; 
    import org.simpleframework.xml.Element; 
    import org.simpleframework.xml.ElementList; 
    import org.simpleframework.xml.Root; 
    import org.simpleframework.xml.Serializer; 
    import org.simpleframework.xml.core.Persister; 

    class Fruit { 
     @Attribute(name = "id") 
     protected final int id; 
     Fruit(
       @Attribute(name = "id") 
       int id) { 
      this.id = id; 
     } 
     int getObjectId() { 
      return id; 
     } 
    } 

    @Root 
    class Apple extends Fruit { 
     private final int sugar; 
     @Element(type = Fruit.class) 
     public Apple(
       @Attribute(name = "id") 
       int id, 
       @Element(name = "sugar") 
       int sugar) { 
      super(id); 
      this.sugar = sugar; 
     } 

     @Element(name = "sugar") 
     public int getSugar() { 
      return this.sugar; 
     } 

     @Override 
     public String toString() { 
      return "id: " + id + ", sugar: " + sugar; 
     } 
    } 

    @Root 
    class Orange extends Fruit { 
     @Attribute 
     public double weight; 

     public Orange(
       @Attribute(name = "id") 
       int id) { 
      super(id); 
     } 

     @Override 
     public String toString() { 
      return "id: " + id + ", weight: " + weight; 
     } 
    } 

    @Root 
    public class Example1 { 
     @ElementList 
     public ArrayList<Fruit> things = new ArrayList<Fruit>(); 

     @Override 
     public String toString() { 
      StringBuilder sb = new StringBuilder(); 
      sb.append("things:\n"); 
      for (int i=0; i<things.size(); i++) { 
       sb.append(" " + things.get(i).toString() + "\n"); 
      } 
      return sb.toString(); 
     } 


     ////////////////////////////////// 

     static Example1 createDummy() { 
      Example1 d = new Example1(); 
      d.things.add(new Apple(17, 212)); 
      Orange or = new Orange(25); 
      or.weight = 11.2; 
      d.things.add(or); 
      return d; 
     } 

     static String msg; 
     static Example1 res; 

     static public String getMessage() { 
      String m = msg; 
      msg = null; 
      return m; 
     } 

     static public boolean write(String path) { 
      Serializer serializer = new Persister(); 
      Example1 example = Example1.createDummy(); 
      File result = new File(path); 

      try { 
       serializer.write(example, result); 
      } catch (Exception e) { 
       e.printStackTrace(); 
       msg = e.getMessage(); 
       return false; 
      } 
      return true; 
     } 

     static public boolean read(String path) { 
      Serializer serializer = new Persister(); 
      File source = new File(path); 

      try { 
       res = serializer.read(Example1.class, source); 
      } catch (Exception e) { 
       e.printStackTrace(); 
       msg = e.getMessage(); 
       return false; 
      } 
      return true; 
     } 

     public static Object getResult() { 
      return res; 
     } 
    }

來源

2013-03-14 Gisela

幾個小時後，我找到了解決辦法。您只需

閱讀手冊

使用@ElementListUnion註釋

package com.mumpitz.simplexmltest; 

import java.io.File; 
import java.util.ArrayList; 
import java.util.List; 

import org.simpleframework.xml.Attribute; 
import org.simpleframework.xml.Element; 
import org.simpleframework.xml.ElementList; 
import org.simpleframework.xml.ElementListUnion; 
import org.simpleframework.xml.Root; 
import org.simpleframework.xml.Serializer; 
import org.simpleframework.xml.core.Persister; 

// the base class 
@Element 
class Thing { 

    static int count=0; 

    Thing() { 
     this.id = ++count; 
    } 

    @Attribute 
    protected int id; 

    public int getId() { 
     return id; 
    } 
} 

// first derived class 
@Element 
class Car extends Thing { 
    @Attribute 
    private String name; 

    Car(@Attribute(name="name") String name) { 
     this.name = name; 
    } 

    public String getName() { 
     return name; 
    } 
    @Override 
    public String toString() { 
     return "ID: " + id + " Car: " + name; 
    } 
} 

// second derived class 
@Element 
class House extends Thing { 
    @Attribute 
    private int price; 

    House(@Attribute(name="price") int price) { 
     this.price = price; 
    } 

    public int getPrice() { 
     return this.price; 
    } 
    @Override 
    public String toString() { 
     return "ID: " + id + " House: " + price; 
    } 
} 


// a class with a list of base class instances 
@Root(name="ListOfThings") 
public class Example4 { 

    // specify the derived classes used in the list 
    @ElementListUnion({ 
     @ElementList(entry="house", inline=true, type=House.class), 
     @ElementList(entry="car", inline=true, type=Car.class) 
    }) 
    private ArrayList<Thing> list = new ArrayList<Thing>(); 

    public void add(Thing t) { 
     list.add(t); 
    } 

    public List<Thing> getProperties() { 
     return list; 
    } 

    @Override 
    public String toString() { 
     StringBuilder sb = new StringBuilder(); 
     sb.append("Example4 contains " + list.size() + " elements:\n"); 
     for (Thing t : list) { 
      sb.append(" " + t.toString() + "\n"); 
     } 
     return sb.toString(); 
    } 


    ////////////////////////////////// 
    // test code 
    ////////////////////////////////// 
    static String msg; 
    static Example4 res; 

    static public String getMessage() { 
     String m = msg; 
     msg = null; 
     return m; 
    } 

    static private Example4 createDummy() { 
     Example4 d = new Example4(); 
     d.add(new Car("Mercedes")); 
     d.add(new House(34000000)); 
     d.add(new Car("VW")); 
     d.add(new House(230000)); 
     return d; 
    } 

    ////////////////////////////////// 
    // serialize/deserialize 
    ////////////////////////////////// 
    static public boolean write(String path) { 

     Serializer serializer = new Persister(); 
     File result = new File(path); 
     Example4 example = Example4.createDummy(); 

     try { 
      serializer.write(example, result); 
     } catch (Exception e) { 
      e.printStackTrace(); 
      msg = e.getMessage(); 
      return false; 
     } 
     return true; 
    } 

    static public boolean read(String path) { 
     Serializer serializer = new Persister(); 
     File source = new File(path); 

     try { 
      res = serializer.read(Example4.class, source); 
     } catch (Exception e) { 
      e.printStackTrace(); 
      msg = e.getMessage(); 
      return false; 
     } 
     return true; 
    } 

    public static Object getResult() { 
     return res; 
    } 
}

來源

2013-03-15 06:38:10 Gisela

Simple-XML - 如何序列化集合中的派生類？

回答

相關問題