Java tutorial
/* * 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 org.apache.commons.collections.Predicate; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import java.lang.reflect.InvocationTargetException; /** * <p><code>Predicate</code> that evaluates a property value against a specified value.</p> * <p> * An implementation of <code>org.apache.commons.collections.Predicate</code> that evaluates a * property value on the object provided against a specified value and returns <code>true</code> * if equal; <code>false</code> otherwise. * The <code>BeanPropertyValueEqualsPredicate</code> constructor takes two parameters which * determine what property will be evaluated on the target object and what its expected value should * be. * <dl> * <dt> * <strong><code> * <pre>public BeanPropertyValueEqualsPredicate( String propertyName, Object propertyValue )</pre> * </code></strong> * </dt> * <dd> * Will create a <code>Predicate</code> that will evaluate the target object and return * <code>true</code> if the property specified by <code>propertyName</code> has a value which * is equal to the the value specified by <code>propertyValue</code>. Or return * <code>false</code> otherwise. * </dd> * </dl> * </p> * <p> * <strong>Note:</strong> Property names 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 closure * BeanPropertyValueEqualsPredicate predicate = * new BeanPropertyValueEqualsPredicate( "activeEmployee", Boolean.FALSE ); * * // filter the Collection * CollectionUtils.filter( peopleCollection, predicate ); * </pre></code> * </p> * <p> * This would take a <code>Collection</code> of person objects and filter out any people whose * <code>activeEmployee</code> property is <code>false</code>. 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>getActiveEmployee()</code> method which returns * the boolean value for the object's <code>activeEmployee</code> property. * </li> * </ul> * </p> * <p> * Another typical usage might look like: * <code><pre> * // create the closure * BeanPropertyValueEqualsPredicate predicate = * new BeanPropertyValueEqualsPredicate( "personId", "456-12-1234" ); * * // search the Collection * CollectionUtils.find( peopleCollection, predicate ); * </pre><code> * </p> * <p> * This would search a <code>Collection</code> of person objects and return the first object whose * <code>personId</code> property value equals <code>456-12-1234</code>. 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>getPersonId()</code> method which returns * the value for the object's <code>personId</code> property. * </li> * </ul> * </p> * * @author Norm Deane * @see org.apache.commons.beanutils.PropertyUtils * @see org.apache.commons.collections.Predicate */ public class BeanPropertyValueEqualsPredicate implements Predicate { /** For logging. */ private final Log log = LogFactory.getLog(this.getClass()); /** * The name of the property which will be evaluated when this <code>Predicate</code> is executed. */ private String propertyName; /** * The value that the property specified by <code>propertyName</code> * will be compared to when this <code>Predicate</code> executes. */ private Object propertyValue; /** * <p>Should <code>null</code> objects in the property path be ignored?</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>false</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; /** * Constructor which takes the name of the property, its expected value to be used in evaluation, * and assumes <code>ignoreNull</code> to be <code>false</code>. * * @param propertyName The name of the property that will be evaluated against the expected value. * @param propertyValue The value to use in object evaluation. * @throws IllegalArgumentException If the property name provided is null or empty. */ public BeanPropertyValueEqualsPredicate(String propertyName, Object propertyValue) { this(propertyName, propertyValue, false); } /** * Constructor which takes the name of the property, its expected value * to be used in evaluation, 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 evaluated against the expected value. * @param propertyValue The value to use in object evaluation. * @param ignoreNull Determines whether <code>null</code> objects in the property path will * genenerate an <code>IllegalArgumentException</code> or not. * @throws IllegalArgumentException If the property name provided is null or empty. */ public BeanPropertyValueEqualsPredicate(String propertyName, Object propertyValue, boolean ignoreNull) { super(); if ((propertyName != null) && (propertyName.length() > 0)) { this.propertyName = propertyName; this.propertyValue = propertyValue; this.ignoreNull = ignoreNull; } else { throw new IllegalArgumentException("propertyName cannot be null or empty"); } } /** * Evaulates the object provided against the criteria specified when this * <code>BeanPropertyValueEqualsPredicate</code> was constructed. Equality is based on * either reference or logical equality as defined by the property object's equals method. 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 evaluated. * @return True if the object provided meets all the criteria for this <code>Predicate</code>; * false otherwise. * @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 boolean evaluate(Object object) { boolean evaluation = false; try { evaluation = evaluateValue(propertyValue, PropertyUtils.getProperty(object, propertyName)); } catch (IllegalArgumentException e) { final String errorMsg = "Problem during evaluation. 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 = "Property not found."; IllegalArgumentException iae = new IllegalArgumentException(errorMsg); if (!BeanUtils.initCause(iae, e)) { log.error(errorMsg, e); } throw iae; } return evaluation; } /** * Utility method which evaluates whether the actual property value equals the expected property * value. * * @param expected The expected value. * @param actual The actual value. * @return True if they are equal; false otherwise. */ protected boolean evaluateValue(Object expected, Object actual) { return (expected == actual) || ((expected != null) && expected.equals(actual)); } /** * Returns the name of the property which will be evaluated when this <code>Predicate</code> is * executed. * * @return The name of the property which will be evaluated when this <code>Predicate</code> is * executed. */ public String getPropertyName() { return propertyName; } /** * Returns the value that the property specified by <code>propertyName</code> will be compared to * when this <code>Predicate</code> executes. * * @return The value that the property specified by <code>propertyName</code> will be compared to * when this <code>Predicate</code> executes. */ public Object getPropertyValue() { return propertyValue; } /** * 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>false</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; } }