com.adaptris.jdbc.JdbcResultSetImpl.java Source code

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Here is the source code for com.adaptris.jdbc.JdbcResultSetImpl.java

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/*
 * Copyright 2015 Adaptris Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.adaptris.jdbc;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.NoSuchElementException;

import org.apache.commons.lang.StringUtils;

import com.adaptris.core.util.JdbcUtil;

public class JdbcResultSetImpl implements JdbcResultSet {

    private ResultSet resultSet;

    public JdbcResultSetImpl(ResultSet resultSet) {
        this.resultSet = resultSet;
    }

    /* (non-Javadoc)
     * @see com.adaptris.jdbc.JdbcResultSet#getRows()
     */
    @Override
    public Iterable<JdbcResultRow> getRows() {
        return new Iterable<JdbcResultRow>() {

            @Override
            public Iterator<JdbcResultRow> iterator() {
                try {
                    switch (resultSet.getType()) {
                    case ResultSet.TYPE_FORWARD_ONLY:
                        return new ForwardOnlyResultSetIterator(resultSet);

                    case ResultSet.TYPE_SCROLL_SENSITIVE:
                    case ResultSet.TYPE_SCROLL_INSENSITIVE:
                        return new ScrollableResultSetIterator(resultSet);

                    default:
                        throw new RuntimeException("ResultSet was of unknown type");
                    }
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
        };
    }

    @Override
    public void close() {
        JdbcUtil.closeQuietly(resultSet);
    }

    /**
     * ScrollableResultSetIterator works only for ResultSets that support .isAfterLast() but
     * follows the ResultSet API most closely by not 'pre-taking' any elements until next()
     * is called.
     */
    private static class ScrollableResultSetIterator implements Iterator<JdbcResultRow> {
        private final ResultSet resultSet;

        private ScrollableResultSetIterator(ResultSet resultSet) {
            this.resultSet = resultSet;
        }

        @Override
        public boolean hasNext() {
            try {
                return !resultSet.isAfterLast();
            } catch (SQLException e) {
                return false;
            }
        }

        @Override
        public JdbcResultRow next() {
            try {
                if (resultSet.next()) {
                    return mapRow(resultSet);
                } else {
                    throw new NoSuchElementException();
                }
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }
    }

    /**
     * ForwardOnlyResultSetIterator works for ResultSets that don't support .isAfterLast(), which
     * is optional for TYPE_FORWARD_ONLY ResultSets. It works by 'pre-taking' an element and hasNext()
     * reports whether that was successful. Side effects of that are that constructing this ResultSet
     * can throw an Exception and having multiple ForwardOnlyResultSetIterators on a single ResultSet
     * will cause issues.
     */
    private static class ForwardOnlyResultSetIterator implements Iterator<JdbcResultRow> {
        private final ResultSet resultSet;
        private JdbcResultRow nextRow;

        private ForwardOnlyResultSetIterator(ResultSet resultSet) {
            this.resultSet = resultSet;
            nextRow = takeNext();
        }

        @Override
        public boolean hasNext() {
            return nextRow != null;
        }

        @Override
        public JdbcResultRow next() {
            if (hasNext()) {
                JdbcResultRow tmp = nextRow;
                nextRow = takeNext();
                return tmp;
            } else {
                throw new NoSuchElementException();
            }
        }

        private JdbcResultRow takeNext() {
            try {
                if (resultSet.next()) {
                    return mapRow(resultSet);
                } else {
                    return null;
                }
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }
    }

    private static JdbcResultRow mapRow(ResultSet resultSet) throws SQLException {
        ResultSetMetaData rsmd = resultSet.getMetaData();
        int columnCount = rsmd.getColumnCount();

        JdbcResultRow row = new JdbcResultRow();
        for (int counter = 1; counter <= columnCount; counter++) {
            row.setFieldValue(StringUtils.defaultIfEmpty(rsmd.getColumnLabel(counter), rsmd.getColumnName(counter)),
                    resultSet.getObject(counter), rsmd.getColumnType(counter));
        }
        return row;
    }
}