basicrowprocessor.java

实现了从Google

        Object bean = this.newInstance(type);

        for (int i = 1; i <= cols; i++) {

            if (columnToProperty[i] == PROPERTY_NOT_FOUND) {
                continue;
            }
            
            Object value = rs.getObject(i);

            PropertyDescriptor prop = props[columnToProperty[i]];
            Class propType = prop.getPropertyType();

            if (propType != null && value == null && propType.isPrimitive()) {
                value = primitiveDefaults.get(propType);
            }

            this.callSetter(bean, prop, value);
        }

        return bean;
    }

    /**
     * The positions in the returned array represent column numbers.  The values
     * stored at each position represent the index in the PropertyDescriptor[] 
     * for the bean property that matches the column name.  If no bean property
     * was found for a column, the position is set to PROPERTY_NOT_FOUND.
     * 
     * @param rsmd The result set meta data containing column information
     * @param props The bean property descriptors
     * @return An int[] with column index to property index mappings.  The 0th 
     * element is meaningless as column indexing starts at 1.
     * 
     * @throws SQLException If a database error occurs
     */
    private int[] mapColumnsToProperties(
        ResultSetMetaData rsmd,
        PropertyDescriptor[] props)
        throws SQLException {

        int cols = rsmd.getColumnCount();
        int columnToProperty[] = new int[cols + 1];

        for (int col = 1; col <= cols; col++) {
            String columnName = rsmd.getColumnName(col);
            for (int i = 0; i < props.length; i++) {

                if (columnName.equalsIgnoreCase(props[i].getName())) {
                    columnToProperty[col] = i;
                    break;

                } else {
                    columnToProperty[col] = PROPERTY_NOT_FOUND;
                }
            }
        }

        return columnToProperty;
    }

    /**
     * Convert a <code>ResultSet</code> row into a <code>Map</code>.  This 
     * implementation returns a <code>Map</code> with case insensitive column
     * names as keys.  Calls to <code>map.get("COL")</code> and 
     * <code>map.get("col")</code> return the same value.
     * @see org.apache.commons.dbutils.RowProcessor#toMap(java.sql.ResultSet)
     */
    public Map toMap(ResultSet rs) throws SQLException {
        Map result = new CaseInsensitiveHashMap();
        ResultSetMetaData rsmd = rs.getMetaData();
        int cols = rsmd.getColumnCount();

        for (int i = 1; i <= cols; i++) {
            result.put(rsmd.getColumnName(i), rs.getObject(i));
        }

        return result;
    }

    /**
     * Calls the setter method on the target object for the given property.
     * If no setter method exists for the property, this method does nothing.
     * @param target The object to set the property on.
     * @param prop The property to set.
     * @param value The value to pass into the setter.
     * @throws SQLException if an error occurs setting the property.
     */
    private void callSetter(
        Object target,
        PropertyDescriptor prop,
        Object value)
        throws SQLException {

        Method setter = prop.getWriteMethod();

        if (setter == null) {
            return;
        }

        Class[] params = setter.getParameterTypes();
        try {
            // Don't call setter if the value object isn't the right type 
            if (this.isCompatibleType(value, params[0])) {
                setter.invoke(target, new Object[] { value });
            }

        } catch (IllegalArgumentException e) {
            throw new SQLException(
                "Cannot set " + prop.getName() + ": " + e.getMessage());

        } catch (IllegalAccessException e) {
            throw new SQLException(
                "Cannot set " + prop.getName() + ": " + e.getMessage());

        } catch (InvocationTargetException e) {
            throw new SQLException(
                "Cannot set " + prop.getName() + ": " + e.getMessage());
        }
    }

    /**
     * ResultSet.getObject() returns an Integer object for an INT column.  The
     * setter method for the property might take an Integer or a primitive int.
     * This method returns true if the value can be successfully passed into
     * the setter method.  Remember, Method.invoke() handles the unwrapping
     * of Integer into an int.
     * 
     * @param value The value to be passed into the setter method.
     * @param type The setter's parameter type.
     * @return boolean True if the value is compatible.
     */
    private boolean isCompatibleType(Object value, Class type) {
        // Do object check first, then primitives
        if (value == null || type.isInstance(value)) {
            return true;

        } else if (
            type.equals(Integer.TYPE) && Integer.class.isInstance(value)) {
            return true;

        } else if (type.equals(Long.TYPE) && Long.class.isInstance(value)) {
            return true;

        } else if (
            type.equals(Double.TYPE) && Double.class.isInstance(value)) {
            return true;

        } else if (type.equals(Float.TYPE) && Float.class.isInstance(value)) {
            return true;

        } else if (type.equals(Short.TYPE) && Short.class.isInstance(value)) {
            return true;

        } else if (type.equals(Byte.TYPE) && Byte.class.isInstance(value)) {
            return true;

        } else if (
            type.equals(Character.TYPE) && Character.class.isInstance(value)) {
            return true;

        } else if (
            type.equals(Boolean.TYPE) && Boolean.class.isInstance(value)) {
            return true;

        } else {
            return false;
        }

    }

    /**
     * Returns a new instance of the given Class.
     *
     * @param c The Class to create an object from.
     * @return A newly created object of the Class.
     * @throws SQLException if creation failed.
     */
    private Object newInstance(Class c) throws SQLException {
        try {
            return c.newInstance();

        } catch (InstantiationException e) {
            throw new SQLException(
                "Cannot create " + c.getName() + ": " + e.getMessage());

        } catch (IllegalAccessException e) {
            throw new SQLException(
                "Cannot create " + c.getName() + ": " + e.getMessage());
        }
    }

    /**
     * Returns a PropertyDescriptor[] for the given Class.
     *
     * @param c The Class to retrieve PropertyDescriptors for.
     * @return A PropertyDescriptor[] describing the Class.
     * @throws SQLException if introspection failed.
     */
    private PropertyDescriptor[] propertyDescriptors(Class c)
        throws SQLException {
        // Introspector caches BeanInfo classes for better performance
        BeanInfo beanInfo = null;
        try {
            beanInfo = Introspector.getBeanInfo(c);

        } catch (IntrospectionException e) {
            throw new SQLException(
                "Bean introspection failed: " + e.getMessage());
        }

        return beanInfo.getPropertyDescriptors();
    }

    /**
     * A Map that converts all keys to lowercase Strings for case insensitive
     * lookups.  This is needed for the toMap() implementation because 
     * databases don't consistenly handle the casing of column names. 
     */
    private static class CaseInsensitiveHashMap extends HashMap {

        /**
         * @see java.util.Map#containsKey(java.lang.Object)
         */
        public boolean containsKey(Object key) {
            return super.containsKey(key.toString().toLowerCase());
        }

        /**
         * @see java.util.Map#get(java.lang.Object)
         */
        public Object get(Object key) {
            return super.get(key.toString().toLowerCase());
        }

        /**
         * @see java.util.Map#put(java.lang.Object, java.lang.Object)
         */
        public Object put(Object key, Object value) {
            return super.put(key.toString().toLowerCase(), value);
        }

        /**
         * @see java.util.Map#putAll(java.util.Map)
         */
        public void putAll(Map m) {
            Iterator iter = m.keySet().iterator();
            while (iter.hasNext()) {
                Object key = iter.next();
                Object value = m.get(key);
                this.put(key, value);
            }
        }

        /**
         * @see java.util.Map#remove(java.lang.ObjecT)
         */
        public Object remove(Object key) {
            return super.remove(key.toString().toLowerCase());
        }
    }
    
}