Change in behavior of XMLEncoder after moving from java 1.6.x to 1.7.x

Question

I've recompiled some of my code under Java 7 and started testing. Quite soon I've noticed that mechanism I used for serialization of objects to xml stopped working. Luckily this serialization is for temporary session storage purpose so I could remove all old serialized XMLs and start from scratch using xstream instead of XMLEncoder.

I'm curious what have I done wrong or what changed in the XMLEncoder shipped with Java7.

B.java:

import java.util.*;
public class B{
        public String s;
        public void setS(String s){
                this.s = s;
        }
        public String getS(){
                return this.s;
        }
        public HashSet<String> h = new HashSet<String>();
        public void setH(HashSet<String> h){
                this.h = h;
        }
        public HashSet<String> getH(){
                return this.h;
        }
}

A.java:

import java.util.*;
import java.io.*;
import java.beans.*;
class A{
        public A(){
                B tmp = new B();
                tmp.setS("abc");
                HashSet<String>h = new HashSet<String>(Arrays.asList("a", "c"));
                tmp.setH(h);

                ByteArrayOutputStream bos = new ByteArrayOutputStream();
                XMLEncoder e = new XMLEncoder( new BufferedOutputStream(bos) );
                e.writeObject( tmp );
                e.close();
                System.out.println(bos.toString());
        }
        public static void main(String []arg){
                new A();
        }
}

Running A under java 1.6.x gives me:

<?xml version="1.0" encoding="UTF-8"?>
<java version="1.6.0_25" class="java.beans.XMLDecoder">
 <object class="B">
  <void property="h">
   <void method="add">
    <string>b</string>
   </void>
   <void method="add">
    <string>a</string>
   </void>
  </void>
  <void property="s">
   <string>abc</string>
  </void>
 </object>
</java>

Running A under java 1.7.0_01 gives me:

<?xml version="1.0" encoding="UTF-8"?>
<java version="1.7.0_01" class="java.beans.XMLDecoder">
 <object class="B" id="B0">
  <void class="B" method="getField">
   <string>s</string>
   <void method="set">
    <object idref="B0"/>
    <string>abc</string>
   </void>
  </void>
 </object>
</java>

As you can see the output does not contain any trace of the HashSet h field.

I've done some googling but so far the only similar case that I could find is this post, nothing else.

Thanks in advance for your hints.

Answer 1

You need to make your data members private in Class B and it will work fine. try this code.

private String s;
private HashSet<String> h = new HashSet<String>();

You need to follow java conventions in defining all your classes. XMLEncode will use getter/setter methods to properly convert objects into xml.