org.apache.commons.beanutils2.ResultSetDynaClass Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of commons-beanutils2 Show documentation
Apache Commons BeanUtils provides an easy-to-use but flexible wrapper around reflection and introspection.
The newest version!
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.beanutils2;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.Objects;

/**
 * Implementation of {@code DynaClass} for DynaBeans that wrap the
 * {@code java.sql.Row objects of a java.sql.ResultSet}.
 * The normal usage pattern is something like:

 *  *   ResultSet rs = ...;
 *   ResultSetDynaClass rsdc = new ResultSetDynaClass(rs);
 *   Iterator rows = rsdc.iterator();
 *   while (rows.hasNext())  {
 *     DynaBean row = (DynaBean) rows.next();
 *     ... process this row ...
 *   }
 *   rs.close();
 * 
 *
 * Each column in the result set will be represented as a DynaBean
 * property of the corresponding name (optionally forced to lower case
 * for portability).
 *
 * WARNING - Any {@link DynaBean} instance returned by
 * this class, or from the {@code Iterator} returned by the
 * {@code iterator()} method, is directly linked to the row that the
 * underlying result set is currently positioned at.  This has the following
 * implications:
 * 
 * Once you retrieve a different {@link DynaBean} instance, you should
 *     no longer use any previous instance.
 * Changing the position of the underlying result set will change the
 *     data that the {@link DynaBean} references.
 * Once the underlying result set is closed, the {@link DynaBean}
 *     instance may no longer be used.
 * 
 *
 * Any database data that you wish to utilize outside the context of the
 * current row of an open result set must be copied.  For example, you could
 * use the following code to create standalone copies of the information in
 * a result set:
 *  *   List results = new ArrayList(); // To hold copied list
 *   ResultSetDynaClass rsdc = ...;
 *   DynaProperty[] properties = rsdc.getDynaProperties();
 *   BasicDynaClass bdc =
 *     new BasicDynaClass("foo", BasicDynaBean.class,
 *                        rsdc.getDynaProperties());
 *   Iterator rows = rsdc.iterator();
 *   while (rows.hasNext()) {
 *     DynaBean oldRow = (DynaBean) rows.next();
 *     DynaBean newRow = bdc.newInstance();
 *     PropertyUtils.copyProperties(newRow, oldRow);
 *     results.add(newRow);
 *   }
 * 
 *
 */

public class ResultSetDynaClass extends JDBCDynaClass {

    private static final long serialVersionUID = 1L;



    /**
     * Construct a new ResultSetDynaClass for the specified
     * {@code ResultSet}.  The property names corresponding
     * to column names in the result set will be lower cased.
     *
     * @param resultSet The result set to be wrapped
     *
     * @throws NullPointerException if {@code resultSet}
     *  is {@code null}
     * @throws SQLException if the metadata for this result set
     *  cannot be introspected
     */
    public ResultSetDynaClass(final ResultSet resultSet) throws SQLException {

        this(resultSet, true);

    }

    /**
     * Construct a new ResultSetDynaClass for the specified
     * {@code ResultSet}.  The property names corresponding
     * to the column names in the result set will be lower cased or not,
     * depending on the specified {@code lowerCase} value.
     *
     * WARNING - If you specify {@code false}
     * for {@code lowerCase}, the returned property names will
     * exactly match the column names returned by your JDBC driver.
     * Because different drivers might return column names in different
     * cases, the property names seen by your application will vary
     * depending on which JDBC driver you are using.
     *
     * @param resultSet The result set to be wrapped
     * @param lowerCase Should property names be lower cased?
     *
     * @throws NullPointerException if {@code resultSet}
     *  is {@code null}
     * @throws SQLException if the metadata for this result set
     *  cannot be introspected
     */
    public ResultSetDynaClass(final ResultSet resultSet, final boolean lowerCase)
        throws SQLException {

        this(resultSet, lowerCase, false);

    }

    /**
     * Construct a new ResultSetDynaClass for the specified
     * {@code ResultSet}.  The property names corresponding
     * to the column names in the result set will be lower cased or not,
     * depending on the specified {@code lowerCase} value.
     *
     * WARNING - If you specify {@code false}
     * for {@code lowerCase}, the returned property names will
     * exactly match the column names returned by your JDBC driver.
     * Because different drivers might return column names in different
     * cases, the property names seen by your application will vary
     * depending on which JDBC driver you are using.
     *
     * @param resultSet The result set to be wrapped
     * @param lowerCase Should property names be lower cased?
     * @param useColumnLabel true if the column label should be used, otherwise false
     *
     * @throws NullPointerException if {@code resultSet}
     *  is {@code null}
     * @throws SQLException if the metadata for this result set
     *  cannot be introspected
     * @since 1.8.3
     */
    public ResultSetDynaClass(final ResultSet resultSet, final boolean lowerCase, final boolean useColumnLabel)
        throws SQLException {
        Objects.requireNonNull(resultSet, "resultSet");
        this.resultSet = resultSet;
        this.lowerCase = lowerCase;
        setUseColumnLabel(useColumnLabel);
        introspect(resultSet);

    }



    /**
     * The {@code ResultSet} we are wrapping.
     */
    protected ResultSet resultSet;



    /**
     * Return an {@code Iterator} of {@link DynaBean} instances for
     * each row of the wrapped {@code ResultSet}, in "forward" order.
     * Unless the underlying result set supports scrolling, this method
     * should be called only once.
     * @return An {@code Iterator} of {@link DynaBean} instances
     */
    public Iterator iterator() {

        return new ResultSetIterator(this);

    }

    /**
     * Get a value from the {@link ResultSet} for the specified
     * property name.
     *
     * @param name The property name
     * @return The value
     * @throws SQLException if an error occurs
     * @since 1.8.0
     */
    public Object getObjectFromResultSet(final String name) throws SQLException {
        return getObject(getResultSet(), name);
    }



    /**
     * Return the result set we are wrapping.
     */
    ResultSet getResultSet() {

        return this.resultSet;

    }



    /**
     * Loads the class of the given name which by default uses the class loader used
     * to load this library.
     * Derivations of this class could implement alternative class loading policies such as
     * using custom ClassLoader or using the Threads's context class loader etc.
     * 
     * @param className The name of the class to load
     * @return The loaded class
     * @throws SQLException if the class cannot be loaded
     */
    @Override
    protected Class loadClass(final String className) throws SQLException {

        try {
            return getClass().getClassLoader().loadClass(className);
        }
        catch (final Exception e) {
            throw new SQLException("Cannot load column class '" +
                                   className + "': " + e);
        }
    }
}