ResultSetWrapper.java

/*
 * Copyright (c) 2002 Cunningham & Cunningham, Inc.
 * Copyright (c) 2009-2015 by Jochen Wierum & Cologne Intelligence
 *
 * This file is part of FitGoodies.
 *
 * FitGoodies is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * FitGoodies is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with FitGoodies.  If not, see <http://www.gnu.org/licenses/>.
*/

package de.cologneintelligence.fitgoodies.database.dynamic;

import de.cologneintelligence.fitgoodies.types.ScientificDouble;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;


/**
 * Maps a ResultSet to an Array of dynamic generated objects.
 * These objects can be read from fit.
 */
public class ResultSetWrapper {
    private final List<String> names = new ArrayList<>();
    private final List<Class<?>> types = new ArrayList<>();
    private final List<Object[]> rows = new ArrayList<>();
    private final ResultSet resultSet;
    private final int columnCount;
    private Class<?> clazz;

    private int analyzeRow() throws SQLException {
        Object[] row = new Object[columnCount];
        int result = 0;

        for (int col = 0; col < columnCount; ++col) {
            row[col] = resultSet.getObject(col + 1);

            if (types.get(col) == null && row[col] != null) {
                Class<?> c = row[col].getClass();
                if (c.equals(Float.class) || c.equals(Float.TYPE)
                    || c.equals(Double.class) || c.equals(Double.TYPE)) {
                    c = ScientificDouble.class;
                }
                types.set(col, c);
                ++result;
            }
        }
        rows.add(row);

        return result;
    }

    /**
     * Generates a new wrapper which maps {@code rs}.
     *
     * @param source {@code ResultSet} to wrap
     * @throws SQLException generated by {@code rs} while reading it.
     */
    public ResultSetWrapper(final ResultSet source) throws SQLException {
        int found = 0;

        ResultSetMetaData meta = source.getMetaData();
        columnCount = meta.getColumnCount();
        for (int i = 1; i <= columnCount; ++i) {
            types.add(null);
        }

        this.resultSet = source;
        while (found < columnCount && source.next()) {
            found += analyzeRow();
        }

        makeClass(meta);
    }

    private void makeClass(final ResultSetMetaData meta) throws SQLException {
        DynamicObjectFactory factory = new DynamicObjectFactory();
        for (int i = 1; i <= columnCount; ++i) {
            String columnName = meta.getColumnName(i);
            names.add(columnName);

            if (types.get(i - 1) == null) {
                types.set(i - 1, Object.class);
            }

            try {
                factory.add(
                       types.get(i - 1),
                        columnName);
            } catch (ClassNotFoundException e) {
                throw new RuntimeException(e);
            }
        }
        clazz = factory.compile();
    }

    /**
     * Creates a new, empty object which has the same fields as the saved
     * {@code ResultSet}.
     *
     * @return dynamic object for one record set
     */
    public final Object createContainerObject() {
        try {
            return clazz.newInstance();
        } catch (InstantiationException | IllegalAccessException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Generates an array which represents the whole {@code ResultSet}.
     * Each element equates to one row in the {@code ResultSet}.
     * The elements have public fields with the same name as the {@code ResultSet} columns.
     * The {@link ScientificDouble} class is automatically used.
     * They can be read them using reflections.
     *
     * @return array of dynamic objects
     * @throws SQLException thrown, if the {@code ResultSet} throws an Exception
     */
    public final Object[] getRows() throws SQLException {
        List<Object> result = new ArrayList<>();

        while (rows.size() > 0) {
            Object[] copy = rows.remove(0);
            Object o = createContainerObject();

            for (int i = 0; i < columnCount; ++i) {
                setObjectValue(o, names.get(i), copy[i]);
            }

            result.add(o);
        }

        while (resultSet.next()) {
            Object o = createContainerObject();
            for (int col = 0; col < columnCount; ++col) {
                setObjectValue(o, names.get(col), resultSet.getObject(col + 1));
            }
            result.add(o);
        }

        return result.toArray();
    }

    private void setObjectValue(
        final Object o, final String valueName, final Object value) {
        try {
            if (mustConvertToScientificDouble(o, valueName, value)) {
                ScientificDouble sdbl = new ScientificDouble((Double) value);
                o.getClass().getField(valueName).set(o, sdbl);
            } else {
                o.getClass().getField(valueName).set(o, value);
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private boolean mustConvertToScientificDouble(final Object o,
                                                  final String valueName, final Object value) throws NoSuchFieldException {
        Class<?> destClass = o.getClass().getField(valueName).getType();
        return destClass.equals(ScientificDouble.class)
            && !value.getClass().equals(ScientificDouble.class);
    }

    /**
     * Gets the class of the dynamic generated object.
     *
     * @return Class of the dynamic generated object.
     */
    public final Class<?> getClazz() {
        return clazz;
    }
}