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From rdon...@apache.org
Subject cvs commit: jakarta-commons/beanutils/optional/bean-collections/src/java/org/apache/commons/beanutils BeanToPropertyValueTransformer.java
Date Mon, 10 May 2004 19:58:32 GMT
rdonkin     2004/05/10 12:58:32

  Added:       beanutils/optional/bean-collections/src/java/org/apache/commons/beanutils
                        BeanToPropertyValueTransformer.java
  Log:
  Added new directory for bean collection components
  
  Revision  Changes    Path
  1.1                  jakarta-commons/beanutils/optional/bean-collections/src/java/org/apache/commons/beanutils/BeanToPropertyValueTransformer.java
  
  Index: BeanToPropertyValueTransformer.java
  ===================================================================
  /*
   * Copyright 2001-2004 The Apache Software Foundation.
   * 
   * Licensed 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 org.apache.commons.collections.Transformer;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import java.lang.reflect.InvocationTargetException;
  
  
  /**
   * <p><code>Transformer</code> that outputs a property value.</p>
   *
   * <p>An implementation of <code>org.apache.commons.collections.Transformer</code>
that transforms
   * the object provided by returning the value of a specified property of the object.  The
   * constructor for <code>BeanToPropertyValueTransformer</code> 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</code>.
If any
   * object in the property path specified by <code>propertyName</code> is <code>null</code>
then the
   * outcome is based on the value of the <code>ignoreNull</code> attribute.
   * </p>
   *
   * <p>
   * A typical usage might look like:
   * <code><pre>
   * // create the transformer
   * BeanToPropertyValueTransformer transformer = new BeanToPropertyValueTransformer( "person.address.city"
);
   *
   * // transform the Collection
   * Collection peoplesCities = CollectionUtils.collect( peopleCollection, transformer );
   * </pre></code>
   * </p>
   *
   * <p>
   * This would take a <code>Collection</code> of person objects and return a
<code>Collection</code>
   * of objects which represents the cities in which each person lived. Assuming...
   * <ul>
   *    <li>
   *       The top level object in the <code>peeopleCollection</code> is an object
which represents a
   *       person.
   *    </li>
   *    <li>
   *       The person object has a <code>getAddress()</code> method which returns
an object which
   *       represents a person's address.
   *    </li>
   *    <li>
   *       The address object has a <code>getCity()</code> 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 <code>IllegalArgumentException</code>?</p>
       * <p>
       * Determines whether <code>null</code> objects in the property path will
genenerate an
       * <code>IllegalArgumentException</code> or not. If set to <code>true</code>
then if any objects
       * in the property path evaluate to <code>null</code> then the
       * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code>
will be logged but
       * not rethrown and <code>null</code> will be returned.  If set to <code>false</code>
then if any
       * objects in the property path evaluate to <code>null</code> then the
       * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code>
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</code> to be <code>false</code>.
       *
       * @param propertyName The name of the property that will be used in the transformation.
       * @throws IllegalArgumentException If the <code>propertyName</code> is
<code>null</code> 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</code> objects in the property
path will
       * genenerate an <code>IllegalArgumentException</code> or not.
       *
       * @param propertyName The name of the property that will be used in the transformation.
       * @param ignoreNull Determines whether <code>null</code> objects in the
property path will
       * genenerate an <code>IllegalArgumentException</code> or not.
       * @throws IllegalArgumentException If the <code>propertyName</code> is
<code>null</code> 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</code> then the outcome will be based on the value of the
<code>ignoreNull</code>
       * attribute. By default, <code>ignoreNull</code> is <code>false</code>
and would result in an
       * <code>IllegalArgumentException</code> if an object in the property path
leading up to the
       * target property is <code>null</code>.
       *
       * @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</code>
and
       * <code>ignoreNull</code> is set to <code>false</code>.
       */
      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 {
                  log.error("ERROR: " + errorMsg, e);
                  throw e;
              }
          } catch (IllegalAccessException e) {
              final String errorMsg = "Unable to access the property provided.";
              log.error(errorMsg, e);
              throw new IllegalArgumentException(errorMsg);
          } catch (InvocationTargetException e) {
              final String errorMsg = "Exception occurred in property's getter";
              log.error(errorMsg, e);
              throw new IllegalArgumentException(errorMsg);
          } catch (NoSuchMethodException e) {
              final String errorMsg = "No property found for name [" +
                  propertyName + "]";
              log.error(errorMsg, e);
              throw new IllegalArgumentException(errorMsg);
          }
  
          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</code> objects in
the property path will
       * genenerate an <code>IllegalArgumentException</code> or not. If set to
<code>true</code> then
       * if any objects in the property path evaluate to <code>null</code> then
the
       * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code>
will be logged but
       * not rethrown and <code>null</code> will be returned.  If set to <code>false</code>
then if any
       * objects in the property path evaluate to <code>null</code> then the
       * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code>
will be logged and
       * rethrown.
       *
       * @return The flag which determines whether <code>null</code> objects in
the property path will
       * genenerate an <code>IllegalArgumentException</code> or not.
       */
      public boolean isIgnoreNull() {
          return ignoreNull;
      }
  }
  
  
  

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