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/**
 * 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.lang3.builder;

import static org.apache.commons.lang3.reflect.FieldUtils.readField;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.reflect.FieldUtils;

/**
 * 

* Assists in implementing {@link Diffable#diff(Object)} methods. *

*

* All non-static, non-transient fields (including inherited fields) * of the objects to diff are discovered using reflection and compared * for differences. *

* *

* To use this class, write code as follows: *

* *
 * public class Person implements Diffable<Person> {
 *   String name;
 *   int age;
 *   boolean smoker;
 *   ...
 *
 *   public DiffResult diff(Person obj) {
 *     // No need for null check, as NullPointerException correct if obj is null
 *     return new ReflectionDiffBuilder(this, obj, ToStringStyle.SHORT_PREFIX_STYLE)
 *       .build();
 *   }
 * }
 * 
* *

* The {@code ToStringStyle} passed to the constructor is embedded in the * returned {@code DiffResult} and influences the style of the * {@code DiffResult.toString()} method. This style choice can be overridden by * calling {@link DiffResult#toString(ToStringStyle)}. *

* @see Diffable * @see Diff * @see DiffResult * @see ToStringStyle * @since 3.6 */ public class ReflectionDiffBuilder implements Builder { private final Object left; private final Object right; private final DiffBuilder diffBuilder; /** *

* Constructs a builder for the specified objects with the specified style. *

* *

* If {@code lhs == rhs} or {@code lhs.equals(rhs)} then the builder will * not evaluate any calls to {@code append(...)} and will return an empty * {@link DiffResult} when {@link #build()} is executed. *

* @param * type of the objects to diff * @param lhs * {@code this} object * @param rhs * the object to diff against * @param style * the style will use when outputting the objects, {@code null} * uses the default * @throws IllegalArgumentException * if {@code lhs} or {@code rhs} is {@code null} */ public ReflectionDiffBuilder(final T lhs, final T rhs, final ToStringStyle style) { this.left = lhs; this.right = rhs; diffBuilder = new DiffBuilder(lhs, rhs, style); } @Override public DiffResult build() { if (left.equals(right)) { return diffBuilder.build(); } appendFields(left.getClass()); return diffBuilder.build(); } private void appendFields(final Class clazz) { for (final Field field : FieldUtils.getAllFields(clazz)) { if (accept(field)) { try { diffBuilder.append(field.getName(), readField(field, left, true), readField(field, right, true)); } catch (final IllegalAccessException ex) { //this can't happen. Would get a Security exception instead //throw a runtime exception in case the impossible happens. throw new InternalError("Unexpected IllegalAccessException: " + ex.getMessage()); } } } } private boolean accept(final Field field) { if (field.getName().indexOf(ClassUtils.INNER_CLASS_SEPARATOR_CHAR) != -1) { return false; } if (Modifier.isTransient(field.getModifiers())) { return false; } return !Modifier.isStatic(field.getModifiers()); } }




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