Re: [Simple-support] erialize/deserialize Lists with empty Strings

[<Nia...@ub...>]

Hi,

Your suggestion should work fine. I think there may be another
alternative using a strategy, so that you could have.

<testData>
   <_values class="java.util.Arrays$ArrayList">
      <string>A</string>
      <string null="false"></string>
      <string null="true"></string>
   </_values>
</testData> 

This would basically involve adding an attribute to all elements where
the value to be written is null. Don't know if deserialization would
respect this though so I would have to investigate. Bottom line though
is that StAX does not treat <string></string> and </string> differently
which would have provided a really nice way to differentiate "" from
null.

Regards,
Niall

-----Original Message-----
From: Joe [mailto:fis...@ya...] 
Sent: 16 December 2008 16:07
To: Gallagher, Niall-N
Cc: sim...@li...
Subject: Re: [Simple-support] erialize/deserialize Lists with empty
Strings

Hi,

> So it looks like if you really need the empty string "" then you will 
> need to either treat null as a special case, or substitute "" for some

> token such as "NULL".
I think i will use a slightly different approach, inspired by the base64
encoding example in your tutorial.
I encode every value with a prefix (here '*') only null values are
ignored.

So
Arrays.asList("A", "", null)

will be serialized as:

<testData>
   <_values class="java.util.Arrays$ArrayList">
      <string>*A</string>
      <string>*</string>
      <string></string>
   </_values>
</testData>

Using @Commit the deserialization can be adjusted, to getting back the
original values.

The output of the following example is the expected String:
values: [A, , null]

public class TestData
{
    @ElementList()
    private List<String> _values = new ArrayList<String>();

    public List<String> getValues()
    {
        return _values;
    }

    public void setValues(List<String> values)
    {
        _values = values;
    }

    @Persist
    public void persist()
    {
        for (int i = 0; i < _values.size(); i++)
            if (_values.get(i) != null)
                _values.set(i, "*" + _values.get(i));
            else
                _values.set(i, "");
    }

    @Commit
    public void commit()
    {
        for (int i = 0; i < _values.size(); i++)
        {
            String val = _values.get(i);
            if (val != null)
                _values.set(i, _values.get(i).substring(1));
        }
    }
    public static void main(String[] args) throws Exception
    {
        Serializer serializer = new Persister();
        File xmlFile = new File("test.xml");
        TestData data = new TestData();
        data.setValues(Arrays.asList("A", "", null));
        serializer.write(data, xmlFile);
        TestData sqlData = serializer.read(TestData.class, xmlFile);
        System.out.println("values: " + sqlData.getValues());
    }
}

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