Hi Nenad,
Nice question !
One way would be to write a filter function to do the lookup for you.
Something like this...
import org.geotools.filter.FunctionExpressionImpl;
public class ExternalLookupFunction extends FunctionExpressionImpl {
public ExternalLookupFunction() {
super("ExternalLookup");
}
@Override
public int getArgCount() {
return 4;
}
@Override
public Object evaluate(Object feature) {
Object returnValue = null;
// get the value from the feature to lookup in the external
// table join field
Object joinValue = getExpression(0).evaluate(feature);
String tableName = getExpression(1).evaluate(feature, String.class);
String joinFieldName = getExpression(2).evaluate(feature, String.class);
String valueFieldName = getExpression(3).evaluate(feature,
String.class);
// Connect to table (or check for existing connection, cache etc. as
// relevant to your app)
// ...
// Look up join value in external table join field to identify
table record
// ...
// Get value from value field and return it
// ...
return returnValue;
}
}
Then (I think) you can refer to this in your SLD document like this.
<FeatureTypeStyle>
<Rule>
<Filter>
<PropertyIsEqualTo>
<Function name="ExternalLookup">
<PropertyName>some feature attribute</PropertyName>
<Literal>external table name</Literal>
<Literal>external table join field</Literal>
<Literal>external table value field</Literal>
</Function>
<Literal>35</Literal>
</PropertyIsEqualTo>
</Filter>
Someone else here will probably have a much easier way of doing all that :-)
Hope this helps - please let us know.
Michael
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