    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.configuration2;
    019
    020import javax.sql.DataSource;
    021import java.sql.Clob;
    022import java.sql.Connection;
    023import java.sql.PreparedStatement;
    024import java.sql.ResultSet;
    025import java.sql.SQLException;
    026import java.sql.Statement;
    027import java.util.ArrayList;
    028import java.util.Collection;
    029import java.util.Iterator;
    030import java.util.List;
    031
    032import org.apache.commons.configuration2.convert.DisabledListDelimiterHandler;
    033import org.apache.commons.configuration2.convert.ListDelimiterHandler;
    034import org.apache.commons.configuration2.event.ConfigurationErrorEvent;
    035import org.apache.commons.configuration2.event.ConfigurationEvent;
    036import org.apache.commons.configuration2.event.EventType;
    037import org.apache.commons.configuration2.io.ConfigurationLogger;
    038import org.apache.commons.lang3.StringUtils;
    039
    040/**
    041 * Configuration stored in a database. The properties are retrieved from a table containing at least one column for the
    042 * keys, and one column for the values. It's possible to store several configurations in the same table by adding a
    043 * column containing the name of the configuration. The name of the table and the columns have to be specified using the
    044 * corresponding properties.
    045 * <p>
    046 * The recommended way to create an instance of {@code DatabaseConfiguration} is to use a <em>configuration
    047 * builder</em>. The builder is configured with a special parameters object defining the database structures used by the
    048 * configuration. Such an object can be created using the {@code database()} method of the {@code Parameters} class. See
    049 * the examples below for more details.
    050 * </p>
    051 *
    052 * <p>
    053 * <strong>Example 1 - One configuration per table</strong>
    054 * </p>
    055 *
    056 * <pre>
    057 * CREATE TABLE myconfig (
    058 *     `key`   VARCHAR NOT NULL PRIMARY KEY,
    059 *     `value` VARCHAR
    060 * );
    061 *
    062 * INSERT INTO myconfig (key, value) VALUES ('foo', 'bar');
    063 *
    064 * BasicConfigurationBuilder&lt;DatabaseConfiguration&gt; builder =
    065 *     new BasicConfigurationBuilder&lt;DatabaseConfiguration&gt;(DatabaseConfiguration.class);
    066 * builder.configure(
    067 *     Parameters.database()
    068 *         .setDataSource(dataSource)
    069 *         .setTable("myconfig")
    070 *         .setKeyColumn("key")
    071 *         .setValueColumn("value")
    072 * );
    073 * Configuration config = builder.getConfiguration();
    074 * String value = config.getString("foo");
    075 * </pre>
    076 *
    077 * <p>
    078 * <strong>Example 2 - Multiple configurations per table</strong>
    079 * </p>
    080 *
    081 * <pre>
    082 * CREATE TABLE myconfigs (
    083 *     `name`  VARCHAR NOT NULL,
    084 *     `key`   VARCHAR NOT NULL,
    085 *     `value` VARCHAR,
    086 *     CONSTRAINT sys_pk_myconfigs PRIMARY KEY (`name`, `key`)
    087 * );
    088 *
    089 * INSERT INTO myconfigs (name, key, value) VALUES ('config1', 'key1', 'value1');
    090 * INSERT INTO myconfigs (name, key, value) VALUES ('config2', 'key2', 'value2');
    091 *
    092 * BasicConfigurationBuilder&lt;DatabaseConfiguration&gt; builder =
    093 *     new BasicConfigurationBuilder&lt;DatabaseConfiguration&gt;(DatabaseConfiguration.class);
    094 * builder.configure(
    095 *     Parameters.database()
    096 *         .setDataSource(dataSource)
    097 *         .setTable("myconfigs")
    098 *         .setKeyColumn("key")
    099 *         .setValueColumn("value")
    100 *         .setConfigurationNameColumn("name")
    101 *         .setConfigurationName("config1")
    102 * );
    103 * Configuration config1 = new DatabaseConfiguration(dataSource, "myconfigs", "name", "key", "value", "config1");
    104 * String value1 = conf.getString("key1");
    105 * </pre>
    106 *
    107 * The configuration can be instructed to perform commits after database updates. This is achieved by setting the
    108 * {@code commits} parameter of the constructors to <b>true</b>. If commits should not be performed (which is the
    109 * default behavior), it should be ensured that the connections returned by the {@code DataSource} are in auto-commit
    110 * mode.
    111 *
    112 * <h1>Note: Like JDBC itself, protection against SQL injection is left to the user.</h1>
    113 *
    114 * @since 1.0
    115 *
    116 */
    117public class DatabaseConfiguration extends AbstractConfiguration {
    118    /** Constant for the statement used by getProperty. */
    119    private static final String SQL_GET_PROPERTY = "SELECT * FROM %s WHERE %s =?";
    120
    121    /** Constant for the statement used by isEmpty. */
    122    private static final String SQL_IS_EMPTY = "SELECT count(*) FROM %s WHERE 1 = 1";
    123
    124    /** Constant for the statement used by clearProperty. */
    125    private static final String SQL_CLEAR_PROPERTY = "DELETE FROM %s WHERE %s =?";
    126
    127    /** Constant for the statement used by clear. */
    128    private static final String SQL_CLEAR = "DELETE FROM %s WHERE 1 = 1";
    129
    130    /** Constant for the statement used by getKeys. */
    131    private static final String SQL_GET_KEYS = "SELECT DISTINCT %s FROM %s WHERE 1 = 1";
    132
    133    /** The data source to connect to the database. */
    134    private DataSource dataSource;
    135
    136    /** The configurationName of the table containing the configurations. */
    137    private String table;
    138
    139    /** The column containing the configurationName of the configuration. */
    140    private String configurationNameColumn;
    141
    142    /** The column containing the keys. */
    143    private String keyColumn;
    144
    145    /** The column containing the values. */
    146    private String valueColumn;
    147
    148    /** The configurationName of the configuration. */
    149    private String configurationName;
    150
    151    /** A flag whether commits should be performed by this configuration. */
    152    private boolean autoCommit;
    153
    154    /**
    155     * Creates a new instance of {@code DatabaseConfiguration}.
    156     */
    157    public DatabaseConfiguration() {
    158        initLogger(new ConfigurationLogger(DatabaseConfiguration.class));
    159        addErrorLogListener();
    160    }
    161
    162    /**
    163     * Returns the {@code DataSource} for obtaining database connections.
    164     *
    165     * @return the {@code DataSource}
    166     */
    167    public DataSource getDataSource() {
    168        return dataSource;
    169    }
    170
    171    /**
    172     * Sets the {@code DataSource} for obtaining database connections.
    173     *
    174     * @param dataSource the {@code DataSource}
    175     */
    176    public void setDataSource(final DataSource dataSource) {
    177        this.dataSource = dataSource;
    178    }
    179
    180    /**
    181     * Returns the name of the table containing configuration data.
    182     *
    183     * @return the name of the table to be queried
    184     */
    185    public String getTable() {
    186        return table;
    187    }
    188
    189    /**
    190     * Sets the name of the table containing configuration data.
    191     *
    192     * @param table the table name
    193     */
    194    public void setTable(final String table) {
    195        this.table = table;
    196    }
    197
    198    /**
    199     * Returns the name of the table column with the configuration name.
    200     *
    201     * @return the name of the configuration name column
    202     */
    203    public String getConfigurationNameColumn() {
    204        return configurationNameColumn;
    205    }
    206
    207    /**
    208     * Sets the name of the table column with the configuration name.
    209     *
    210     * @param configurationNameColumn the name of the column with the configuration name
    211     */
    212    public void setConfigurationNameColumn(final String configurationNameColumn) {
    213        this.configurationNameColumn = configurationNameColumn;
    214    }
    215
    216    /**
    217     * Returns the name of the column containing the configuration keys.
    218     *
    219     * @return the name of the key column
    220     */
    221    public String getKeyColumn() {
    222        return keyColumn;
    223    }
    224
    225    /**
    226     * Sets the name of the column containing the configuration keys.
    227     *
    228     * @param keyColumn the name of the key column
    229     */
    230    public void setKeyColumn(final String keyColumn) {
    231        this.keyColumn = keyColumn;
    232    }
    233
    234    /**
    235     * Returns the name of the column containing the configuration values.
    236     *
    237     * @return the name of the value column
    238     */
    239    public String getValueColumn() {
    240        return valueColumn;
    241    }
    242
    243    /**
    244     * Sets the name of the column containing the configuration values.
    245     *
    246     * @param valueColumn the name of the value column
    247     */
    248    public void setValueColumn(final String valueColumn) {
    249        this.valueColumn = valueColumn;
    250    }
    251
    252    /**
    253     * Returns the name of this configuration instance.
    254     *
    255     * @return the name of this configuration
    256     */
    257    public String getConfigurationName() {
    258        return configurationName;
    259    }
    260
    261    /**
    262     * Sets the name of this configuration instance.
    263     *
    264     * @param configurationName the name of this configuration
    265     */
    266    public void setConfigurationName(final String configurationName) {
    267        this.configurationName = configurationName;
    268    }
    269
    270    /**
    271     * Returns a flag whether this configuration performs commits after database updates.
    272     *
    273     * @return a flag whether commits are performed
    274     */
    275    public boolean isAutoCommit() {
    276        return autoCommit;
    277    }
    278
    279    /**
    280     * Sets the auto commit flag. If set to <b>true</b>, this configuration performs a commit after each database update.
    281     *
    282     * @param autoCommit the auto commit flag
    283     */
    284    public void setAutoCommit(final boolean autoCommit) {
    285        this.autoCommit = autoCommit;
    286    }
    287
    288    /**
    289     * Returns the value of the specified property. If this causes a database error, an error event will be generated of
    290     * type {@code READ} with the causing exception. The event's {@code propertyName} is set to the passed in property key,
    291     * the {@code propertyValue} is undefined.
    292     *
    293     * @param key the key of the desired property
    294     * @return the value of this property
    295     */
    296    @Override
    297    protected Object getPropertyInternal(final String key) {
    298        final JdbcOperation<Object> op = new JdbcOperation<Object>(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, key, null) {
    299            @Override
    300            protected Object performOperation() throws SQLException {
    301                final List<Object> results = new ArrayList<>();
    302                try (final ResultSet rs = openResultSet(String.format(SQL_GET_PROPERTY, table, keyColumn), true, key)) {
    303                    while (rs.next()) {
    304                        final Object value = extractPropertyValue(rs);
    305                        // Split value if it contains the list delimiter
    306                        for (final Object o : getListDelimiterHandler().parse(value)) {
    307                            results.add(o);
    308                        }
    309                    }
    310                }
    311                if (!results.isEmpty()) {
    312                    return results.size() > 1 ? results : results.get(0);
    313                }
    314                return null;
    315            }
    316        };
    317
    318        return op.execute();
    319    }
    320
    321    /**
    322     * Adds a property to this configuration. If this causes a database error, an error event will be generated of type
    323     * {@code ADD_PROPERTY} with the causing exception. The event's {@code propertyName} is set to the passed in property
    324     * key, the {@code propertyValue} points to the passed in value.
    325     *
    326     * @param key the property key
    327     * @param obj the value of the property to add
    328     */
    329    @Override
    330    protected void addPropertyDirect(final String key, final Object obj) {
    331        new JdbcOperation<Void>(ConfigurationErrorEvent.WRITE, ConfigurationEvent.ADD_PROPERTY, key, obj) {
    332            @Override
    333            protected Void performOperation() throws SQLException {
    334                final StringBuilder query = new StringBuilder("INSERT INTO ");
    335                query.append(table).append(" (");
    336                query.append(keyColumn).append(", ");
    337                query.append(valueColumn);
    338                if (configurationNameColumn != null) {
    339                    query.append(", ").append(configurationNameColumn);
    340                }
    341                query.append(") VALUES (?, ?");
    342                if (configurationNameColumn != null) {
    343                    query.append(", ?");
    344                }
    345                query.append(")");
    346
    347                try (final PreparedStatement pstmt = initStatement(query.toString(), false, key, String.valueOf(obj))) {
    348                    if (configurationNameColumn != null) {
    349                        pstmt.setString(3, configurationName);
    350                    }
    351
    352                    pstmt.executeUpdate();
    353                    return null;
    354                }
    355            }
    356        }.execute();
    357    }
    358
    359    /**
    360     * Adds a property to this configuration. This implementation temporarily disables list delimiter parsing, so that even
    361     * if the value contains the list delimiter, only a single record is written into the managed table. The implementation
    362     * of {@code getProperty()} takes care about delimiters. So list delimiters are fully supported by
    363     * {@code DatabaseConfiguration}, but internally treated a bit differently.
    364     *
    365     * @param key the key of the new property
    366     * @param value the value to be added
    367     */
    368    @Override
    369    protected void addPropertyInternal(final String key, final Object value) {
    370        final ListDelimiterHandler oldHandler = getListDelimiterHandler();
    371        try {
    372            // temporarily disable delimiter parsing
    373            setListDelimiterHandler(DisabledListDelimiterHandler.INSTANCE);
    374            super.addPropertyInternal(key, value);
    375        } finally {
    376            setListDelimiterHandler(oldHandler);
    377        }
    378    }
    379
    380    /**
    381     * Checks if this configuration is empty. If this causes a database error, an error event will be generated of type
    382     * {@code READ} with the causing exception. Both the event's {@code propertyName} and {@code propertyValue} will be
    383     * undefined.
    384     *
    385     * @return a flag whether this configuration is empty.
    386     */
    387    @Override
    388    protected boolean isEmptyInternal() {
    389        final JdbcOperation<Integer> op = new JdbcOperation<Integer>(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, null, null) {
    390            @Override
    391            protected Integer performOperation() throws SQLException {
    392                try (final ResultSet rs = openResultSet(String.format(SQL_IS_EMPTY, table), true)) {
    393                    return rs.next() ? Integer.valueOf(rs.getInt(1)) : null;
    394                }
    395            }
    396        };
    397
    398        final Integer count = op.execute();
    399        return count == null || count.intValue() == 0;
    400    }
    401
    402    /**
    403     * Checks whether this configuration contains the specified key. If this causes a database error, an error event will be
    404     * generated of type {@code READ} with the causing exception. The event's {@code propertyName} will be set to the passed
    405     * in key, the {@code propertyValue} will be undefined.
    406     *
    407     * @param key the key to be checked
    408     * @return a flag whether this key is defined
    409     */
    410    @Override
    411    protected boolean containsKeyInternal(final String key) {
    412        final JdbcOperation<Boolean> op = new JdbcOperation<Boolean>(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, key, null) {
    413            @Override
    414            protected Boolean performOperation() throws SQLException {
    415                try (final ResultSet rs = openResultSet(String.format(SQL_GET_PROPERTY, table, keyColumn), true, key)) {
    416                    return rs.next();
    417                }
    418            }
    419        };
    420
    421        final Boolean result = op.execute();
    422        return result != null && result.booleanValue();
    423    }
    424
    425    /**
    426     * Removes the specified value from this configuration. If this causes a database error, an error event will be
    427     * generated of type {@code CLEAR_PROPERTY} with the causing exception. The event's {@code propertyName} will be set to
    428     * the passed in key, the {@code propertyValue} will be undefined.
    429     *
    430     * @param key the key of the property to be removed
    431     */
    432    @Override
    433    protected void clearPropertyDirect(final String key) {
    434        new JdbcOperation<Void>(ConfigurationErrorEvent.WRITE, ConfigurationEvent.CLEAR_PROPERTY, key, null) {
    435            @Override
    436            protected Void performOperation() throws SQLException {
    437                try (final PreparedStatement ps = initStatement(String.format(SQL_CLEAR_PROPERTY, table, keyColumn), true, key)) {
    438                    ps.executeUpdate();
    439                    return null;
    440                }
    441            }
    442        }.execute();
    443    }
    444
    445    /**
    446     * Removes all entries from this configuration. If this causes a database error, an error event will be generated of
    447     * type {@code CLEAR} with the causing exception. Both the event's {@code propertyName} and the {@code propertyValue}
    448     * will be undefined.
    449     */
    450    @Override
    451    protected void clearInternal() {
    452        new JdbcOperation<Void>(ConfigurationErrorEvent.WRITE, ConfigurationEvent.CLEAR, null, null) {
    453            @Override
    454            protected Void performOperation() throws SQLException {
    455                initStatement(String.format(SQL_CLEAR, table), true).executeUpdate();
    456                return null;
    457            }
    458        }.execute();
    459    }
    460
    461    /**
    462     * Returns an iterator with the names of all properties contained in this configuration. If this causes a database
    463     * error, an error event will be generated of type {@code READ} with the causing exception. Both the event's
    464     * {@code propertyName} and the {@code propertyValue} will be undefined.
    465     *
    466     * @return an iterator with the contained keys (an empty iterator in case of an error)
    467     */
    468    @Override
    469    protected Iterator<String> getKeysInternal() {
    470        final Collection<String> keys = new ArrayList<>();
    471        new JdbcOperation<Collection<String>>(ConfigurationErrorEvent.READ, ConfigurationErrorEvent.READ, null, null) {
    472            @Override
    473            protected Collection<String> performOperation() throws SQLException {
    474                try (final ResultSet rs = openResultSet(String.format(SQL_GET_KEYS, keyColumn, table), true)) {
    475                    while (rs.next()) {
    476                        keys.add(rs.getString(1));
    477                    }
    478                    return keys;
    479                }
    480            }
    481        }.execute();
    482
    483        return keys.iterator();
    484    }
    485
    486    /**
    487     * Returns the used {@code DataSource} object.
    488     *
    489     * @return the data source
    490     * @since 1.4
    491     */
    492    public DataSource getDatasource() {
    493        return dataSource;
    494    }
    495
    496    /**
    497     * Close the specified database objects. Avoid closing if null and hide any SQLExceptions that occur.
    498     *
    499     * @param conn The database connection to close
    500     * @param stmt The statement to close
    501     * @param rs the result set to close
    502     */
    503    protected void close(final Connection conn, final Statement stmt, final ResultSet rs) {
    504        try {
    505            if (rs != null) {
    506                rs.close();
    507            }
    508        } catch (final SQLException e) {
    509            getLogger().error("An error occurred on closing the result set", e);
    510        }
    511
    512        try {
    513            if (stmt != null) {
    514                stmt.close();
    515            }
    516        } catch (final SQLException e) {
    517            getLogger().error("An error occured on closing the statement", e);
    518        }
    519
    520        try {
    521            if (conn != null) {
    522                conn.close();
    523            }
    524        } catch (final SQLException e) {
    525            getLogger().error("An error occured on closing the connection", e);
    526        }
    527    }
    528
    529    /**
    530     * Extracts the value of a property from the given result set. The passed in {@code ResultSet} was created by a SELECT
    531     * statement on the underlying database table. This implementation reads the value of the column determined by the
    532     * {@code valueColumn} property. Normally the contained value is directly returned. However, if it is of type
    533     * {@code CLOB}, text is extracted as string.
    534     *
    535     * @param rs the current {@code ResultSet}
    536     * @return the value of the property column
    537     * @throws SQLException if an error occurs
    538     */
    539    protected Object extractPropertyValue(final ResultSet rs) throws SQLException {
    540        Object value = rs.getObject(valueColumn);
    541        if (value instanceof Clob) {
    542            value = convertClob((Clob) value);
    543        }
    544        return value;
    545    }
    546
    547    /**
    548     * Converts a CLOB to a string.
    549     *
    550     * @param clob the CLOB to be converted
    551     * @return the extracted string value
    552     * @throws SQLException if an error occurs
    553     */
    554    private static Object convertClob(final Clob clob) throws SQLException {
    555        final int len = (int) clob.length();
    556        return len > 0 ? clob.getSubString(1, len) : StringUtils.EMPTY;
    557    }
    558
    559    /**
    560     * An internally used helper class for simplifying database access through plain JDBC. This class provides a simple
    561     * framework for creating and executing a JDBC statement. It especially takes care of proper handling of JDBC resources
    562     * even in case of an error.
    563     *
    564     * @param <T> the type of the results produced by a JDBC operation
    565     */
    566    private abstract class JdbcOperation<T> {
    567        /** Stores the connection. */
    568        private Connection conn;
    569
    570        /** Stores the statement. */
    571        private PreparedStatement pstmt;
    572
    573        /** Stores the result set. */
    574        private ResultSet resultSet;
    575
    576        /** The type of the event to send in case of an error. */
    577        private final EventType<? extends ConfigurationErrorEvent> errorEventType;
    578
    579        /** The type of the operation which caused an error. */
    580        private final EventType<?> operationEventType;
    581
    582        /** The property configurationName for an error event. */
    583        private final String errorPropertyName;
    584
    585        /** The property value for an error event. */
    586        private final Object errorPropertyValue;
    587
    588        /**
    589         * Creates a new instance of {@code JdbcOperation} and initializes the properties related to the error event.
    590         *
    591         * @param errEvType the type of the error event
    592         * @param opType the operation event type
    593         * @param errPropName the property configurationName for the error event
    594         * @param errPropVal the property value for the error event
    595         */
    596        protected JdbcOperation(final EventType<? extends ConfigurationErrorEvent> errEvType, final EventType<?> opType, final String errPropName,
    597            final Object errPropVal) {
    598            errorEventType = errEvType;
    599            operationEventType = opType;
    600            errorPropertyName = errPropName;
    601            errorPropertyValue = errPropVal;
    602        }
    603
    604        /**
    605         * Executes this operation. This method obtains a database connection and then delegates to {@code performOperation()}.
    606         * Afterwards it performs the necessary clean up. Exceptions that are thrown during the JDBC operation are caught and
    607         * transformed into configuration error events.
    608         *
    609         * @return the result of the operation
    610         */
    611        public T execute() {
    612            T result = null;
    613
    614            try {
    615                conn = getDatasource().getConnection();
    616                result = performOperation();
    617
    618                if (isAutoCommit()) {
    619                    conn.commit();
    620                }
    621            } catch (final SQLException e) {
    622                fireError(errorEventType, operationEventType, errorPropertyName, errorPropertyValue, e);
    623            } finally {
    624                close(conn, pstmt, resultSet);
    625            }
    626
    627            return result;
    628        }
    629
    630        /**
    631         * Returns the current connection. This method can be called while {@code execute()} is running. It returns <b>null</b>
    632         * otherwise.
    633         *
    634         * @return the current connection
    635         */
    636        protected Connection getConnection() {
    637            return conn;
    638        }
    639
    640        /**
    641         * Creates a {@code PreparedStatement} object for executing the specified SQL statement.
    642         *
    643         * @param sql the statement to be executed
    644         * @param nameCol a flag whether the configurationName column should be taken into account
    645         * @return the prepared statement object
    646         * @throws SQLException if an SQL error occurs
    647         */
    648        protected PreparedStatement createStatement(final String sql, final boolean nameCol) throws SQLException {
    649            final String statement;
    650            if (nameCol && configurationNameColumn != null) {
    651                final StringBuilder buf = new StringBuilder(sql);
    652                buf.append(" AND ").append(configurationNameColumn).append("=?");
    653                statement = buf.toString();
    654            } else {
    655                statement = sql;
    656            }
    657
    658            pstmt = getConnection().prepareStatement(statement);
    659            return pstmt;
    660        }
    661
    662        /**
    663         * Creates an initializes a {@code PreparedStatement} object for executing an SQL statement. This method first calls
    664         * {@code createStatement()} for creating the statement and then initializes the statement's parameters.
    665         *
    666         * @param sql the statement to be executed
    667         * @param nameCol a flag whether the configurationName column should be taken into account
    668         * @param params the parameters for the statement
    669         * @return the initialized statement object
    670         * @throws SQLException if an SQL error occurs
    671         */
    672        protected PreparedStatement initStatement(final String sql, final boolean nameCol, final Object... params) throws SQLException {
    673            final PreparedStatement ps = createStatement(sql, nameCol);
    674
    675            int idx = 1;
    676            for (final Object param : params) {
    677                ps.setObject(idx++, param);
    678            }
    679            if (nameCol && configurationNameColumn != null) {
    680                ps.setString(idx, configurationName);
    681            }
    682
    683            return ps;
    684        }
    685
    686        /**
    687         * Creates a {@code PreparedStatement} for a query, initializes it and executes it. The resulting {@code ResultSet} is
    688         * returned.
    689         *
    690         * @param sql the statement to be executed
    691         * @param nameCol a flag whether the configurationName column should be taken into account
    692         * @param params the parameters for the statement
    693         * @return the {@code ResultSet} produced by the query
    694         * @throws SQLException if an SQL error occurs
    695         */
    696        protected ResultSet openResultSet(final String sql, final boolean nameCol, final Object... params) throws SQLException {
    697            return resultSet = initStatement(sql, nameCol, params).executeQuery();
    698        }
    699
    700        /**
    701         * Performs the JDBC operation. This method is called by {@code execute()} after this object has been fully initialized.
    702         * Here the actual JDBC logic has to be placed.
    703         *
    704         * @return the result of the operation
    705         * @throws SQLException if an SQL error occurs
    706         */
    707        protected abstract T performOperation() throws SQLException;
    708    }
    709}