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If your XML data contains a large number of strings with many repetitions
it may be well worth interning these strings. Calling the intern()
method on a String returns a string that has the same contents
as this string, but is guaranteed to be from a pool of unique strings. This
may reduce your memory footprint considerably. So, is there a
simple method for interning all strings resulting from unmarshalling?
There is only two things to do. First, we customize a small change for
the mapping of xsd:string to String, to sneak
in our own method for parsing the XML string data to a Java string.
<jaxb:globalBindings>
<jaxb:javaType name="String"
xmlType="xsd:string"
parseMethod="faststring.StringInterner.parseStringToString"/>
</jaxb:globalBindings>
The other thing is to write the class StringInterner which
contains a tiny wrapper for the method parseString from
DatatypeConverter:
package faststring;
import javax.xml.bind.DatatypeConverter;
public class StringInterner {
public static String parseStringToString( String value ){
return DatatypeConverter.parseString( value ).intern();
}
}
Peeking at the implementation of DatatypeConverter reveals
that parseString just returns its argument. But its a good
strategy to go by the book and call the basic conversion except when
we are prepared to do it all on our own, as in the next example.
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