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BeanUtils provides an easy-to-use but flexible wrapper around reflection and introspection.
/*
* 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.beanutils;
import java.io.Serializable;
import java.sql.Date;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Time;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
/**
* Provides common logic for JDBC implementations of {@link DynaClass}.
*
* @author Craig R. McClanahan
* @author George Franciscus
* @version $Revision: 926529 $ $Date: 2010-03-23 07:44:24 -0400 (Tue, 23 Mar 2010) $
*/
abstract class JDBCDynaClass implements DynaClass, Serializable {
// ----------------------------------------------------- Instance Variables
/**
* Flag defining whether column names should be lower cased when
* converted to property names.
*/
protected boolean lowerCase = true;
/**
* Flag defining whether column names or labels should be used.
*/
private boolean useColumnLabel;
/**
*
The set of dynamic properties that are part of this
* {@link DynaClass}.
*/
protected DynaProperty[] properties = null;
/**
* The set of dynamic properties that are part of this
* {@link DynaClass}, keyed by the property name. Individual descriptor
* instances will be the same instances as those in the
* properties list.
*/
protected Map propertiesMap = new HashMap();
/**
* Cross Reference for column name --> dyna property name
* (needed when lowerCase option is true)
*/
private Map columnNameXref;
// ------------------------------------------------------ DynaClass Methods
/**
* Return the name of this DynaClass (analogous to the
* getName() method of java.lang.ClassDynaClass implementation class to support
* different dynamic classes, with different sets of properties.
*/
public String getName() {
return (this.getClass().getName());
}
/**
* Return a property descriptor for the specified property, if it
* exists; otherwise, return null.
*
* @param name Name of the dynamic property for which a descriptor
* is requested
*
* @exception IllegalArgumentException if no property name is specified
*/
public DynaProperty getDynaProperty(String name) {
if (name == null) {
throw new IllegalArgumentException("No property name specified");
}
return ((DynaProperty) propertiesMap.get(name));
}
/**
* Return an array of ProperyDescriptors for the properties
* currently defined in this DynaClass. If no properties are defined, a
* zero-length array will be returned.
*/
public DynaProperty[] getDynaProperties() {
return (properties);
}
/**
* Instantiate and return a new DynaBean instance, associated
* with this DynaClass. NOTE - This operation is not
* supported, and throws an exception.
*
* @exception IllegalAccessException if the Class or the appropriate
* constructor is not accessible
* @exception InstantiationException if this Class represents an abstract
* class, an array class, a primitive type, or void; or if instantiation
* fails for some other reason
*/
public DynaBean newInstance()
throws IllegalAccessException, InstantiationException {
throw new UnsupportedOperationException("newInstance() not supported");
}
/**
* Set whether the column label or name should be used for the property name.
*
* @param useColumnLabel true if the column label should be used, otherwise false
*/
public void setUseColumnLabel(boolean useColumnLabel) {
this.useColumnLabel = useColumnLabel;
}
/**
* Loads and returns the Class of the given name.
* By default, a load from the thread context class loader is attempted.
* If there is no such class loader, the class loader used to load this
* class will be utilized.
*
* @param className The name of the class to load
* @return The loaded class
* @exception SQLException if an exception was thrown trying to load
* the specified class
*/
protected Class loadClass(String className) throws SQLException {
try {
ClassLoader cl = Thread.currentThread().getContextClassLoader();
if (cl == null) {
cl = this.getClass().getClassLoader();
}
// use Class.forName() - see BEANUTILS-327
return Class.forName(className, false, cl);
} catch (Exception e) {
throw new SQLException(
"Cannot load column class '" + className + "': " + e);
}
}
/**
* Factory method to create a new DynaProperty for the given index
* into the result set metadata.
*
* @param metadata is the result set metadata
* @param i is the column index in the metadata
* @return the newly created DynaProperty instance
* @throws SQLException If an error occurs accessing the SQL metadata
*/
protected DynaProperty createDynaProperty(
ResultSetMetaData metadata,
int i)
throws SQLException {
String columnName = null;
if (useColumnLabel) {
columnName = metadata.getColumnLabel(i);
}
if (columnName == null || columnName.trim().length() == 0) {
columnName = metadata.getColumnName(i);
}
String name = lowerCase ? columnName.toLowerCase() : columnName;
if (!name.equals(columnName)) {
if (columnNameXref == null) {
columnNameXref = new HashMap();
}
columnNameXref.put(name, columnName);
}
String className = null;
try {
int sqlType = metadata.getColumnType(i);
switch (sqlType) {
case java.sql.Types.DATE:
return new DynaProperty(name, java.sql.Date.class);
case java.sql.Types.TIMESTAMP:
return new DynaProperty(name, java.sql.Timestamp.class);
case java.sql.Types.TIME:
return new DynaProperty(name, java.sql.Time.class);
default:
className = metadata.getColumnClassName(i);
}
} catch (SQLException e) {
// this is a patch for HsqlDb to ignore exceptions
// thrown by its metadata implementation
}
// Default to Object type if no class name could be retrieved
// from the metadata
Class clazz = Object.class;
if (className != null) {
clazz = loadClass(className);
}
return new DynaProperty(name, clazz);
}
/**
* Introspect the metadata associated with our result set, and populate
* the properties and propertiesMap instance
* variables.
*
* @param resultSet The resultSet whose metadata is to
* be introspected
*
* @exception SQLException if an error is encountered processing the
* result set metadata
*/
protected void introspect(ResultSet resultSet) throws SQLException {
// Accumulate an ordered list of DynaProperties
ArrayList list = new ArrayList();
ResultSetMetaData metadata = resultSet.getMetaData();
int n = metadata.getColumnCount();
for (int i = 1; i <= n; i++) { // JDBC is one-relative!
DynaProperty dynaProperty = createDynaProperty(metadata, i);
if (dynaProperty != null) {
list.add(dynaProperty);
}
}
// Convert this list into the internal data structures we need
properties =
(DynaProperty[]) list.toArray(new DynaProperty[list.size()]);
for (int i = 0; i < properties.length; i++) {
propertiesMap.put(properties[i].getName(), properties[i]);
}
}
/**
* Get a column value from a {@link ResultSet} for the specified name.
*
* @param resultSet The result set
* @param name The property name
* @return The value
* @throws SQLException if an error occurs
*/
protected Object getObject(ResultSet resultSet, String name) throws SQLException {
DynaProperty property = getDynaProperty(name);
if (property == null) {
throw new IllegalArgumentException("Invalid name '" + name + "'");
}
String columnName = getColumnName(name);
Class type = property.getType();
// java.sql.Date
if (type.equals(Date.class)) {
return resultSet.getDate(columnName);
}
// java.sql.Timestamp
if (type.equals(Timestamp.class)) {
return resultSet.getTimestamp(columnName);
}
// java.sql.Time
if (type.equals(Time.class)) {
return resultSet.getTime(columnName);
}
return resultSet.getObject(columnName);
}
/**
* Get the table column name for the specified property name.
*
* @param name The property name
* @return The column name (which can be different if the lowerCase
* option is used).
*/
protected String getColumnName(String name) {
if (columnNameXref != null && columnNameXref.containsKey(name)) {
return (String)columnNameXref.get(name);
} else {
return name;
}
}
}
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