basicrowprocessor.java

实现了从Google

/*
 * $Header: /home/cvs/jakarta-commons/dbutils/src/java/org/apache/commons/dbutils/BasicRowProcessor.java,v 1.5 2003/11/11 00:53:19 dgraham Exp $
 * $Revision: 1.5 $
 * $Date: 2003/11/11 00:53:19 $
 * 
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact [e-mail].
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 * 5. Products derived from this software may not be called "Apache"
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 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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package org.apache.commons.dbutils;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * Basic implementation of the <code>RowProcessor</code> interface.
 * This class is a thread-safe Singleton.
 * 
 * @see RowProcessor
 * 
 * @author Henri Yandell
 * @author Juozas Baliuka
 * @author David Graham
 * @author Yoav Shapira
 */
public class BasicRowProcessor implements RowProcessor {

    /**
     * Set a bean's primitive properties to these defaults when SQL NULL 
     * is returned.  These are the same as the defaults that ResultSet get* 
     * methods return in the event of a NULL column.
     */
    private static final Map primitiveDefaults = new HashMap();

    static {
        primitiveDefaults.put(Integer.TYPE, new Integer(0));
        primitiveDefaults.put(Short.TYPE, new Short((short) 0));
        primitiveDefaults.put(Byte.TYPE, new Byte((byte) 0));
        primitiveDefaults.put(Float.TYPE, new Float(0));
        primitiveDefaults.put(Double.TYPE, new Double(0));
        primitiveDefaults.put(Long.TYPE, new Long(0));
        primitiveDefaults.put(Boolean.TYPE, Boolean.FALSE);
        primitiveDefaults.put(Character.TYPE, new Character('\u0000'));
    }

    /**
     * Special array index that indicates there is no bean property that
     * matches a column from a ResultSet.
     */
    private static final int PROPERTY_NOT_FOUND = -1;

    /**
     * The Singleton instance of this class.
     */
    private static final BasicRowProcessor instance = new BasicRowProcessor();

    /**
     * Returns the Singleton instance of this class.
     *
     * @return The single instance of this class.
     */
    public static BasicRowProcessor instance() {
        return instance;
    }

    /**
     * Protected constructor for BasicRowProcessor subclasses only.
     */
    protected BasicRowProcessor() {
        super();
    }

    /**
     * Convert a <code>ResultSet</code> row into an <code>Object[]</code>.
     * This implementation copies column values into the array in the same 
     * order they're returned from the <code>ResultSet</code>.  Array elements
     * will be set to <code>null</code> if the column was SQL NULL.
     *
     * @see org.apache.commons.dbutils.RowProcessor#toArray(java.sql.ResultSet)
     */
    public Object[] toArray(ResultSet rs) throws SQLException {
        ResultSetMetaData meta = rs.getMetaData();
        int cols = meta.getColumnCount();
        Object[] result = new Object[cols];

        for (int i = 0; i < cols; i++) {
            result[i] = rs.getObject(i + 1);
        }

        return result;
    }

    /**
     * Convert a <code>ResultSet</code> row into a JavaBean.  This 
     * implementation uses reflection and <code>BeanInfo</code> classes to 
     * match column names to bean property names.  Properties are matched to 
     * columns based on several factors:
     * <br/>
     * <ol>
     *     <li>
     *     The class has a writable property with the same name as a column.
     *     The name comparison is case insensitive.
     *     </li>
     * 
     *     <li>
     *     The property's set method parameter type matches the column 
     *     type. If the data types do not match, the setter will not be called.
     *     </li>
     * </ol>
     * 
     * <p>
     * Primitive bean properties are set to their defaults when SQL NULL is
     * returned from the <code>ResultSet</code>.  Numeric fields are set to 0
     * and booleans are set to false.  Object bean properties are set to 
     * <code>null</code> when SQL NULL is returned.  This is the same behavior
     * as the <code>ResultSet</code> get* methods.
     * </p>
     * 
     * @see org.apache.commons.dbutils.RowProcessor#toBean(java.sql.ResultSet, java.lang.Class)
     */
    public Object toBean(ResultSet rs, Class type) throws SQLException {

        PropertyDescriptor[] props = this.propertyDescriptors(type);

        ResultSetMetaData rsmd = rs.getMetaData();

        int[] columnToProperty = this.mapColumnsToProperties(rsmd, props);

        int cols = rsmd.getColumnCount();

        return this.createBean(rs, type, props, columnToProperty, cols);
    }

    /**
     * Convert a <code>ResultSet</code> into a <code>List</code> of JavaBeans.  
     * This implementation uses reflection and <code>BeanInfo</code> classes to 
     * match column names to bean property names. Properties are matched to 
     * columns based on several factors:
     * <br/>
     * <ol>
     *     <li>
     *     The class has a writable property with the same name as a column.
     *     The name comparison is case insensitive.
     *     </li>
     * 
     *     <li>
     *     The property's set method parameter type matches the column 
     *     type. If the data types do not match, the setter will not be called.
     *     </li>
     * </ol>
     * 
     * <p>
     * Primitive bean properties are set to their defaults when SQL NULL is
     * returned from the <code>ResultSet</code>.  Numeric fields are set to 0
     * and booleans are set to false.  Object bean properties are set to 
     * <code>null</code> when SQL NULL is returned.  This is the same behavior
     * as the <code>ResultSet</code> get* methods.
     * </p>
     * 
     * @see org.apache.commons.dbutils.RowProcessor#toBeanList(java.sql.ResultSet, java.lang.Class)
     */
    public List toBeanList(ResultSet rs, Class type) throws SQLException {
        List results = new ArrayList();

        if (!rs.next()) {
            return results;
        }

        PropertyDescriptor[] props = this.propertyDescriptors(type);
        ResultSetMetaData rsmd = rs.getMetaData();
        int[] columnToProperty = this.mapColumnsToProperties(rsmd, props);
        int cols = rsmd.getColumnCount();

        do {
            results.add(this.createBean(rs, type, props, columnToProperty, cols));

        } while (rs.next());

        return results;
    }

    /**
     * Creates a new object and initializes its fields from the ResultSet.
     *
     * @param rs The result set
     * @param type The bean type (the return type of the object)
     * @param props The property descriptors
     * @param columnToProperty The column indices in the result set
     * @param cols The number of columns
     * @return An initialized object.
     * @throws SQLException If a database error occurs
     */
    private Object createBean(
        ResultSet rs,
        Class type,
        PropertyDescriptor[] props,
        int[] columnToProperty,
        int cols)
        throws SQLException {