package de.intevation.gnv.exports;

import de.intevation.gnv.geobackend.base.Result;
import de.intevation.gnv.geobackend.base.ResultDescriptor;

import de.intevation.gnv.state.exception.StateException;

import java.util.ArrayList;
import java.util.List;

import org.apache.log4j.Logger;

/**
 * This is the default implementation of {@link Export.DataCollector}. This
 * class serves a method to extract required data from <code>Result</code>
 * objects.
 *
 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
 */
public class DefaultDataCollector
implements Export.DataCollector
{
    /**
     * Logger used to log via log4j.
     */
    private   Logger log = Logger.getLogger(DefaultDataCollector.class);

    /**
     * ResultDescriptor used to extract specific attributes from
     * <code>Result</code> object.
     */
    protected ResultDescriptor rd;

    /**
     * Atrribute names in <code>Result</code> object which should be used for
     * data extraction.
     */
    protected String []        names;


    /**
     * Constructor
     *
     * @param names See {@link #names}
     */
    public DefaultDataCollector(String[] names) {
        this.names = names;
    }

    /**
     * This method initializes the <code>ResultDescriptor</code> rd for a faster
     * data extraction.
     *
     * @param res A <code>Result</code> object used to get its description.
     */
    public void init(Result res) {
        rd = res.getResultDescriptor();
    }

    /**
     * This method is used to extract the required data specified by {@link
     * #names}.
     *
     * @param result <code>Result</code> object.
     *
     * @return Extracted data.
     */
    public String[] getData(Result result)
    throws StateException {

        if (rd == null)
            init(result);

        List entries = new ArrayList();

        int[] indices = rd.getColumnIndices(names);
        for (int i = 0; i < names.length; ++i) {
            entries.add(result.getString(indices[i]));
        }

        return (String[]) entries.toArray((new String[entries.size()]));
    }
}
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