ReflectionDiffBuilder.java
/*
* 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
*
* https://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 java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;
import org.apache.commons.lang3.ArraySorter;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.reflect.FieldUtils;
import org.apache.commons.lang3.tuple.Pair;
/**
* 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>{@code
* public class Person implements Diffable<Person> {
* String name;
* int age;
* boolean smoker;
* ...
*
* public DiffResult<Person> diff(Person obj) {
* // No need for null check, as NullPointerException correct if obj is null
* return ReflectionDiffBuilder.<Person>builder()
* .setDiffBuilder(DiffBuilder.<Person>builder()
* .setLeft(this)
* .setRight(obj)
* .setStyle(ToStringStyle.SHORT_PREFIX_STYLE)
* .build())
* .setExcludeFieldNames("userName", "password")
* .build() // -> ReflectionDiffBuilder
* .build(); // -> DiffResult
* }
* }
* }</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>
* <p>
* See {@link DiffBuilder} for a non-reflection based version of this class.
* </p>
*
* @param <T> type of the left and right object to diff.
* @see Diffable
* @see Diff
* @see DiffResult
* @see ToStringStyle
* @see DiffBuilder
* @see AbstractBuilder#setForceAccessible(boolean)
* @since 3.6
*/
public class ReflectionDiffBuilder<T> extends AbstractReflection implements Builder<DiffResult<T>> {
/**
* Constructs a new instance.
*
* @param <T> type of the left and right object.
* @since 3.15.0
*/
public static final class Builder<T> extends AbstractBuilder<Builder<T>> {
private String[] excludeFieldNames = ArrayUtils.EMPTY_STRING_ARRAY;
private DiffBuilder<T> diffBuilder;
/**
* Constructs a new instance.
*/
public Builder() {
// empty
}
/**
* Builds a new configured {@link ReflectionDiffBuilder}.
*
* @return A new configured {@link ReflectionDiffBuilder}.
*/
public ReflectionDiffBuilder<T> build() {
return new ReflectionDiffBuilder<>(this);
}
@Override
public ReflectionDiffBuilder<T> get() {
return build();
}
/**
* Sets the DiffBuilder.
*
* @param diffBuilder The DiffBuilder.
* @return {@code this} instance.
*/
public Builder<T> setDiffBuilder(final DiffBuilder<T> diffBuilder) {
this.diffBuilder = diffBuilder;
return this;
}
/**
* Sets field names to exclude from output. Intended for fields like {@code "password"} or {@code "lastModificationDate"}.
*
* @param excludeFieldNames field names to exclude.
* @return {@code this} instance.
*/
public Builder<T> setExcludeFieldNames(final String... excludeFieldNames) {
this.excludeFieldNames = toExcludeFieldNames(excludeFieldNames);
return this;
}
}
/**
* A registry of objects to detect cyclical object references, avoid infinite loops, and stack overflows.
*/
private static final ThreadLocal<Set<Pair<IDKey, IDKey>>> REGISTRY = ThreadLocal.withInitial(HashSet::new);
/**
* Constructs a new {@link Builder}.
*
* @param <T> type of the left and right object.
* @return A new {@link Builder}.
* @since 3.15.0
*/
public static <T> Builder<T> builder() {
return new Builder<>();
}
/**
* Gets the registry of object pairs being traversed by the reflection
* methods in the current thread.
*
* @return Set the registry of objects being traversed
*/
static Set<Pair<IDKey, IDKey>> getRegistry() {
return REGISTRY.get();
}
/**
* Tests whether the registry contains the given object pair.
* <p>
* Used by the reflection methods to avoid infinite loops.
* Objects might be swapped therefore a check is needed if the object pair
* is registered in the given or swapped order.
* </p>
*
* @param lhs {@code this} object to lookup in registry
* @param rhs The other object to lookup on registry
* @return boolean {@code true} if the registry contains the given object.
*/
static boolean isRegistered(final Object lhs, final Object rhs) {
return isRegistered(lhs, rhs, getRegistry());
}
/**
* Registers the given object pair.
* Used by the reflection methods to avoid infinite loops.
*
* @param lhs {@code this} object to register
* @param rhs the other object to register
*/
static void register(final Object lhs, final Object rhs) {
register(lhs, rhs, getRegistry());
}
private static String[] toExcludeFieldNames(final String[] excludeFieldNames) {
if (excludeFieldNames == null) {
return ArrayUtils.EMPTY_STRING_ARRAY;
}
// clone and remove nulls
return ArraySorter.sort(ReflectionToStringBuilder.toNoNullStringArray(excludeFieldNames));
}
/**
* Unregisters the given object pair.
*
* <p>
* Used by the reflection methods to avoid infinite loops.
* </p>
*
* @param lhs {@code this} object to unregister
* @param rhs the other object to unregister
*/
static void unregister(final Object lhs, final Object rhs) {
unregister(lhs, rhs, getRegistry(), REGISTRY);
}
private final DiffBuilder<T> diffBuilder;
/**
* Field names to exclude from output. Intended for fields like {@code "password"} or {@code "lastModificationDate"}.
*/
private String[] excludeFieldNames;
/**
* Constructs a new instance.
*
* @param builder A non-null Builder.
* @throws NullPointerException Thrown on null input.
*/
private ReflectionDiffBuilder(final Builder<T> builder) {
super(Objects.requireNonNull(builder, "builder"));
this.diffBuilder = Objects.requireNonNull(builder.diffBuilder, "diffBuilder");
this.excludeFieldNames = Objects.requireNonNull(builder.excludeFieldNames, "excludeFieldNames");
}
/**
* Constructs a new instance.
*
* @param diffBuilder A non-null DiffBuilder.
* @param excludeFieldNames A non-null String array.
* @throws NullPointerException Thrown on null input.
*/
private ReflectionDiffBuilder(final DiffBuilder<T> diffBuilder, final String[] excludeFieldNames) {
this(ReflectionDiffBuilder.<T>builder().setDiffBuilder(diffBuilder).setExcludeFieldNames(excludeFieldNames));
}
/**
* Constructs a builder for the specified objects with the specified style.
*
* <p>
* If {@code left == right} or {@code left.equals(right)} 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 left {@code this} object.
* @param right The object to diff against.
* @param style The style will use when outputting the objects, {@code null} uses the default
* @throws IllegalArgumentException if {@code left} or {@code right} is {@code null}.
* @deprecated Use {@link Builder}.
*/
@Deprecated
public ReflectionDiffBuilder(final T left, final T right, final ToStringStyle style) {
this(DiffBuilder.<T>builder().setLeft(left).setRight(right).setStyle(style).build(), ArrayUtils.EMPTY_STRING_ARRAY);
}
private boolean accept(final Field field) {
if (field.getName().indexOf(ClassUtils.INNER_CLASS_SEPARATOR_CHAR) != -1 || Modifier.isTransient(field.getModifiers())
|| Modifier.isStatic(field.getModifiers()) || Arrays.binarySearch(excludeFieldNames, field.getName()) >= 0) {
// Rejected.
return false;
}
return !field.isAnnotationPresent(DiffExclude.class);
}
/**
* Appends fields using reflection.
*
* @throws SecurityException if an underlying accessible object's method denies the request.
* @see SecurityManager#checkPermission
*/
private void appendFields(final Class<?> clazz) {
for (final Field field : FieldUtils.getAllFields(clazz)) {
if (accept(field)) {
try {
if (setAccessible(field)) {
diffBuilder.append(field.getName(), Reflection.getUnchecked(field, getLeft()), Reflection.getUnchecked(field, getRight()));
}
} catch (final RuntimeException e) {
// Ignored as per AccessibleObject / SecurityManager / InaccessibleObjectException
}
}
}
}
/**
* {@inheritDoc}
*
* @throws SecurityException if an underlying accessible object's method denies the request.
* @see SecurityManager#checkPermission
*/
@Override
public DiffResult<T> build() {
if (getLeft() == getRight() || isRegistered(getLeft(), getRight())) {
return diffBuilder.build();
}
try {
register(getLeft(), getRight());
appendFields(getLeft().getClass());
return diffBuilder.build();
} finally {
unregister(getLeft(), getRight());
}
}
/**
* Gets the field names that should be excluded from the diff.
*
* @return The excludeFieldNames.
* @since 3.13.0
*/
public String[] getExcludeFieldNames() {
return excludeFieldNames.clone();
}
private T getLeft() {
return diffBuilder.getLeft();
}
private T getRight() {
return diffBuilder.getRight();
}
/**
* Sets the field names to exclude.
*
* @param excludeFieldNames The field names to exclude from the diff or {@code null}.
* @return {@code this} instance.
* @since 3.13.0
* @deprecated Use {@link Builder#setExcludeFieldNames(String[])}.
*/
@Deprecated
public ReflectionDiffBuilder<T> setExcludeFieldNames(final String... excludeFieldNames) {
this.excludeFieldNames = toExcludeFieldNames(excludeFieldNames);
return this;
}
}