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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.
*
* <p>
* All non-static, non-transient fields (including inherited fields)
* of the objects to diff are discovered using reflection and compared
* for differences.
* </p>
*
* <p>
* To use this class, write code as follows:
* </p>
*
* <pre>
* 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();
* }
* }
* </pre>
*
* <p>
* The {@link ToStringStyle} passed to the constructor is embedded in the
* returned {@link DiffResult} and influences the style of the
* {@code DiffResult.toString()} method. This style choice can be overridden by
* calling {@link DiffResult#toString(ToStringStyle)}.
* </p>
* @param <T>
* type of the left and right object to diff.
* @see Diffable
* @see Diff
* @see DiffResult
* @see ToStringStyle
* @since 3.6
*/
public class ReflectionDiffBuilder<T> implements Builder<DiffResult<T>> {
private final Object left;
private final Object right;
private final DiffBuilder<T> diffBuilder;
/**
* Constructs a builder for the specified objects with the specified style.
*
* <p>
* 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.
* </p>
* @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<T> 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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