The Commons Beanutils BeanToPropertyValueTransformer.java source code
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
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package org.apache.commons.beanutils;
import org.apache.commons.collections.Transformer;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.lang.reflect.InvocationTargetException;
/**
* <p>Transformer that outputs a property value.
*
* <p>An implementation of org.apache.commons.collections.Transformer that transforms
* the object provided by returning the value of a specified property of the object. The
* constructor for <code>BeanToPropertyValueTransformer requires the name of the property
* that will be used in the transformation. The property can be a simple, nested, indexed, or
* mapped property as defined by <code>org.apache.commons.beanutils.PropertyUtils. If any
* object in the property path specified by <code>propertyName is null then the
* outcome is based on the value of the <code>ignoreNull attribute.
* </p>
*
* <p>
* A typical usage might look like:
* <code> * // create the transformer
* BeanToPropertyValueTransformer transformer = new BeanToPropertyValueTransformer( "person.address.city" );
*
* // transform the Collection
* Collection peoplesCities = CollectionUtils.collect( peopleCollection, transformer );
* </pre>
* </p>
*
* <p>
* This would take a <code>Collection of person objects and return a Collection
* of objects which represents the cities in which each person lived. Assuming...
* <ul>
* <li>
* The top level object in the <code>peeopleCollection is an object which represents a
* person.
* </li>
* <li>
* The person object has a <code>getAddress() method which returns an object which
* represents a person's address.
* </li>
* <li>
* The address object has a <code>getCity() method which returns an object which
* represents the city in which a person lives.
* </li>
* </ul>
*
* @author Norm Deane
* @see org.apache.commons.beanutils.PropertyUtils
* @see org.apache.commons.collections.Transformer
*/
public class BeanToPropertyValueTransformer implements Transformer {
/** For logging. */
private final Log log = LogFactory.getLog(this.getClass());
/** The name of the property that will be used in the transformation of the object. */
private String propertyName;
/**
* <p>Should null objects on the property path throw an IllegalArgumentException?
* <p>
* Determines whether <code>null objects in the property path will genenerate an
* <code>IllegalArgumentException or not. If set to true then if any objects
* in the property path evaluate to <code>null then the
* <code>IllegalArgumentException throw by PropertyUtils will be logged but
* not rethrown and <code>null will be returned. If set to false then if any
* objects in the property path evaluate to <code>null then the
* <code>IllegalArgumentException throw by PropertyUtils will be logged and
* rethrown.
* </p>
*/
private boolean ignoreNull;
/**
* Constructs a Transformer which does not ignore nulls.
* Constructor which takes the name of the property that will be used in the transformation and
* assumes <code>ignoreNull to be false.
*
* @param propertyName The name of the property that will be used in the transformation.
* @throws IllegalArgumentException If the <code>propertyName is null or
* empty.
*/
public BeanToPropertyValueTransformer(String propertyName) {
this(propertyName, false);
}
/**
* Constructs a Transformer and sets ignoreNull.
* Constructor which takes the name of the property that will be used in the transformation and
* a boolean which determines whether <code>null objects in the property path will
* genenerate an <code>IllegalArgumentException or not.
*
* @param propertyName The name of the property that will be used in the transformation.
* @param ignoreNull Determines whether <code>null objects in the property path will
* genenerate an <code>IllegalArgumentException or not.
* @throws IllegalArgumentException If the <code>propertyName is null or
* empty.
*/
public BeanToPropertyValueTransformer(String propertyName, boolean ignoreNull) {
super();
if ((propertyName != null) && (propertyName.length() > 0)) {
this.propertyName = propertyName;
this.ignoreNull = ignoreNull;
} else {
throw new IllegalArgumentException(
"propertyName cannot be null or empty");
}
}
/**
* Returns the value of the property named in the transformer's constructor for
* the object provided. If any object in the property path leading up to the target property is
* <code>null then the outcome will be based on the value of the ignoreNull
* attribute. By default, <code>ignoreNull is false and would result in an
* <code>IllegalArgumentException if an object in the property path leading up to the
* target property is <code>null.
*
* @param object The object to be transformed.
* @return The value of the property named in the transformer's constructor for the object
* provided.
* @throws IllegalArgumentException If an IllegalAccessException, InvocationTargetException, or
* NoSuchMethodException is thrown when trying to access the property specified on the object
* provided. Or if an object in the property path provided is <code>null and
* <code>ignoreNull is set to false.
*/
public Object transform(Object object) {
Object propertyValue = null;
try {
propertyValue = PropertyUtils.getProperty(object, propertyName);
} catch (IllegalArgumentException e) {
final String errorMsg = "Problem during transformation. Null value encountered in property path...";
if (ignoreNull) {
log.warn("WARNING: " + errorMsg + e);
} else {
IllegalArgumentException iae = new IllegalArgumentException(errorMsg);
if (!BeanUtils.initCause(iae, e)) {
log.error(errorMsg, e);
}
throw iae;
}
} catch (IllegalAccessException e) {
final String errorMsg = "Unable to access the property provided.";
IllegalArgumentException iae = new IllegalArgumentException(errorMsg);
if (!BeanUtils.initCause(iae, e)) {
log.error(errorMsg, e);
}
throw iae;
} catch (InvocationTargetException e) {
final String errorMsg = "Exception occurred in property's getter";
IllegalArgumentException iae = new IllegalArgumentException(errorMsg);
if (!BeanUtils.initCause(iae, e)) {
log.error(errorMsg, e);
}
throw iae;
} catch (NoSuchMethodException e) {
final String errorMsg = "No property found for name [" +
propertyName + "]";
IllegalArgumentException iae = new IllegalArgumentException(errorMsg);
if (!BeanUtils.initCause(iae, e)) {
log.error(errorMsg, e);
}
throw iae;
}
return propertyValue;
}
/**
* Returns the name of the property that will be used in the transformation of the bean.
*
* @return The name of the property that will be used in the transformation of the bean.
*/
public String getPropertyName() {
return propertyName;
}
/**
* Returns the flag which determines whether <code>null objects in the property path will
* genenerate an <code>IllegalArgumentException or not. If set to true then
* if any objects in the property path evaluate to <code>null then the
* <code>IllegalArgumentException throw by PropertyUtils will be logged but
* not rethrown and <code>null will be returned. If set to false then if any
* objects in the property path evaluate to <code>null then the
* <code>IllegalArgumentException throw by PropertyUtils will be logged and
* rethrown.
*
* @return The flag which determines whether <code>null objects in the property path will
* genenerate an <code>IllegalArgumentException or not.
*/
public boolean isIgnoreNull() {
return ignoreNull;
}
}
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