org.apache.commons.lang3.builder.EqualsBuilder Maven / Gradle / Ivy
/*
* 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 java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.tuple.Pair;
/**
* Assists in implementing {@link Object#equals(Object)} methods.
*
* This class provides methods to build a good equals method for any
* class. It follows rules laid out in
* Effective Java
* , by Joshua Bloch. In particular the rule for comparing doubles,
* floats, and arrays can be tricky. Also, making sure that
* equals() and hashCode() are consistent can be
* difficult.
*
* Two Objects that compare as equals must generate the same hash code,
* but two Objects with the same hash code do not have to be equal.
*
* All relevant fields should be included in the calculation of equals.
* Derived fields may be ignored. In particular, any field used in
* generating a hash code must be used in the equals method, and vice
* versa.
*
* Typical use for the code is as follows:
*
* public boolean equals(Object obj) {
* if (obj == null) { return false; }
* if (obj == this) { return true; }
* if (obj.getClass() != getClass()) {
* return false;
* }
* MyClass rhs = (MyClass) obj;
* return new EqualsBuilder()
* .appendSuper(super.equals(obj))
* .append(field1, rhs.field1)
* .append(field2, rhs.field2)
* .append(field3, rhs.field3)
* .isEquals();
* }
*
*
* Alternatively, there is a method that uses reflection to determine
* the fields to test. Because these fields are usually private, the method,
* reflectionEquals, uses AccessibleObject.setAccessible to
* change the visibility of the fields. This will fail under a security
* manager, unless the appropriate permissions are set up correctly. It is
* also slower than testing explicitly.
*
* A typical invocation for this method would look like:
*
* public boolean equals(Object obj) {
* return EqualsBuilder.reflectionEquals(this, obj);
* }
*
*
* @since 1.0
* @version $Id: EqualsBuilder.java 1091531 2011-04-12 18:29:49Z ggregory $
*/
public class EqualsBuilder implements Builder {
/**
*
* A registry of objects used by reflection methods to detect cyclical object references and avoid infinite loops.
*
*
* @since 3.0
*/
private static final ThreadLocal>> REGISTRY = new ThreadLocal>>();
/*
* NOTE: we cannot store the actual objects in a HashSet, as that would use the very hashCode()
* we are in the process of calculating.
*
* So we generate a one-to-one mapping from the original object to a new object.
*
* Now HashSet uses equals() to determine if two elements with the same hashcode really
* are equal, so we also need to ensure that the replacement objects are only equal
* if the original objects are identical.
*
* The original implementation (2.4 and before) used the System.indentityHashCode()
* method - however this is not guaranteed to generate unique ids (e.g. LANG-459)
*
* We now use the IDKey helper class (adapted from org.apache.axis.utils.IDKey)
* to disambiguate the duplicate ids.
*/
/**
*
* Returns the registry of object pairs being traversed by the reflection
* methods in the current thread.
*
*
* @return Set the registry of objects being traversed
* @since 3.0
*/
static Set> getRegistry() {
return REGISTRY.get();
}
/**
*
* Converters value pair into a register pair.
*
*
* @param lhs this object
* @param rhs the other object
*
* @return the pair
*/
static Pair getRegisterPair(Object lhs, Object rhs) {
IDKey left = new IDKey(lhs);
IDKey right = new IDKey(rhs);
return Pair.of(left, right);
}
/**
*
* Returns true if the registry contains the given object pair.
* 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 given or swapped order.
*
*
* @param lhs this object to lookup in registry
* @param rhs the other object to lookup on registry
* @return boolean true if the registry contains the given object.
* @since 3.0
*/
static boolean isRegistered(Object lhs, Object rhs) {
Set> registry = getRegistry();
Pair pair = getRegisterPair(lhs, rhs);
Pair swappedPair = Pair.of(pair.getLeft(), pair.getRight());
return registry != null
&& (registry.contains(pair) || registry.contains(swappedPair));
}
/**
*
* Registers the given object pair.
* Used by the reflection methods to avoid infinite loops.
*
*
* @param lhs this object to register
* @param rhs the other object to register
*/
static void register(Object lhs, Object rhs) {
synchronized (EqualsBuilder.class) {
if (getRegistry() == null) {
REGISTRY.set(new HashSet>());
}
}
Set> registry = getRegistry();
Pair pair = getRegisterPair(lhs, rhs);
registry.add(pair);
}
/**
*
* Unregisters the given object pair.
*
*
*
* Used by the reflection methods to avoid infinite loops.
*
* @param lhs this object to unregister
* @param rhs the other object to unregister
* @since 3.0
*/
static void unregister(Object lhs, Object rhs) {
Set> registry = getRegistry();
if (registry != null) {
Pair pair = getRegisterPair(lhs, rhs);
registry.remove(pair);
synchronized (EqualsBuilder.class) {
//read again
registry = getRegistry();
if (registry != null && registry.isEmpty()) {
REGISTRY.remove();
}
}
}
}
/**
* If the fields tested are equals.
* The default value is true.
*/
private boolean isEquals = true;
/**
* Constructor for EqualsBuilder.
*
* Starts off assuming that equals is true.
* @see Object#equals(Object)
*/
public EqualsBuilder() {
// do nothing for now.
}
//-------------------------------------------------------------------------
/**
* This method uses reflection to determine if the two Objects
* are equal.
*
* It uses AccessibleObject.setAccessible to gain access to private
* fields. This means that it will throw a security exception if run under
* a security manager, if the permissions are not set up correctly. It is also
* not as efficient as testing explicitly.
*
* Transient members will be not be tested, as they are likely derived
* fields, and not part of the value of the Object.
*
* Static fields will not be tested. Superclass fields will be included.
*
* @param lhs this object
* @param rhs the other object
* @param excludeFields Collection of String field names to exclude from testing
* @return true if the two Objects have tested equals.
*/
public static boolean reflectionEquals(Object lhs, Object rhs, Collection excludeFields) {
return reflectionEquals(lhs, rhs, ReflectionToStringBuilder.toNoNullStringArray(excludeFields));
}
/**
* This method uses reflection to determine if the two Objects
* are equal.
*
* It uses AccessibleObject.setAccessible to gain access to private
* fields. This means that it will throw a security exception if run under
* a security manager, if the permissions are not set up correctly. It is also
* not as efficient as testing explicitly.
*
* Transient members will be not be tested, as they are likely derived
* fields, and not part of the value of the Object.
*
* Static fields will not be tested. Superclass fields will be included.
*
* @param lhs this object
* @param rhs the other object
* @param excludeFields array of field names to exclude from testing
* @return true if the two Objects have tested equals.
*/
public static boolean reflectionEquals(Object lhs, Object rhs, String... excludeFields) {
return reflectionEquals(lhs, rhs, false, null, excludeFields);
}
/**
* This method uses reflection to determine if the two Objects
* are equal.
*
* It uses AccessibleObject.setAccessible to gain access to private
* fields. This means that it will throw a security exception if run under
* a security manager, if the permissions are not set up correctly. It is also
* not as efficient as testing explicitly.
*
* If the TestTransients parameter is set to true, transient
* members will be tested, otherwise they are ignored, as they are likely
* derived fields, and not part of the value of the Object.
*
* Static fields will not be tested. Superclass fields will be included.
*
* @param lhs this object
* @param rhs the other object
* @param testTransients whether to include transient fields
* @return true if the two Objects have tested equals.
*/
public static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients) {
return reflectionEquals(lhs, rhs, testTransients, null);
}
/**
* This method uses reflection to determine if the two Objects
* are equal.
*
* It uses AccessibleObject.setAccessible to gain access to private
* fields. This means that it will throw a security exception if run under
* a security manager, if the permissions are not set up correctly. It is also
* not as efficient as testing explicitly.
*
* If the testTransients parameter is set to true, transient
* members will be tested, otherwise they are ignored, as they are likely
* derived fields, and not part of the value of the Object.
*
* Static fields will not be included. Superclass fields will be appended
* up to and including the specified superclass. A null superclass is treated
* as java.lang.Object.
*
* @param lhs this object
* @param rhs the other object
* @param testTransients whether to include transient fields
* @param reflectUpToClass the superclass to reflect up to (inclusive),
* may be null
* @param excludeFields array of field names to exclude from testing
* @return true if the two Objects have tested equals.
* @since 2.0
*/
public static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients, Class reflectUpToClass,
String... excludeFields) {
if (lhs == rhs) {
return true;
}
if (lhs == null || rhs == null) {
return false;
}
// Find the leaf class since there may be transients in the leaf
// class or in classes between the leaf and root.
// If we are not testing transients or a subclass has no ivars,
// then a subclass can test equals to a superclass.
Class lhsClass = lhs.getClass();
Class rhsClass = rhs.getClass();
Class testClass;
if (lhsClass.isInstance(rhs)) {
testClass = lhsClass;
if (!rhsClass.isInstance(lhs)) {
// rhsClass is a subclass of lhsClass
testClass = rhsClass;
}
} else if (rhsClass.isInstance(lhs)) {
testClass = rhsClass;
if (!lhsClass.isInstance(rhs)) {
// lhsClass is a subclass of rhsClass
testClass = lhsClass;
}
} else {
// The two classes are not related.
return false;
}
EqualsBuilder equalsBuilder = new EqualsBuilder();
try {
reflectionAppend(lhs, rhs, testClass, equalsBuilder, testTransients, excludeFields);
while (testClass.getSuperclass() != null && testClass != reflectUpToClass) {
testClass = testClass.getSuperclass();
reflectionAppend(lhs, rhs, testClass, equalsBuilder, testTransients, excludeFields);
}
} catch (IllegalArgumentException e) {
// In this case, we tried to test a subclass vs. a superclass and
// the subclass has ivars or the ivars are transient and
// we are testing transients.
// If a subclass has ivars that we are trying to test them, we get an
// exception and we know that the objects are not equal.
return false;
}
return equalsBuilder.isEquals();
}
/**
* Appends the fields and values defined by the given object of the
* given Class.
*
* @param lhs the left hand object
* @param rhs the right hand object
* @param clazz the class to append details of
* @param builder the builder to append to
* @param useTransients whether to test transient fields
* @param excludeFields array of field names to exclude from testing
*/
private static void reflectionAppend(
Object lhs,
Object rhs,
Class clazz,
EqualsBuilder builder,
boolean useTransients,
String[] excludeFields) {
if (isRegistered(lhs, rhs)) {
return;
}
try {
register(lhs, rhs);
Field[] fields = clazz.getDeclaredFields();
AccessibleObject.setAccessible(fields, true);
for (int i = 0; i < fields.length && builder.isEquals; i++) {
Field f = fields[i];
if (!ArrayUtils.contains(excludeFields, f.getName())
&& (f.getName().indexOf('$') == -1)
&& (useTransients || !Modifier.isTransient(f.getModifiers()))
&& (!Modifier.isStatic(f.getModifiers()))) {
try {
builder.append(f.get(lhs), f.get(rhs));
} catch (IllegalAccessException e) {
//this can't happen. Would get a Security exception instead
//throw a runtime exception in case the impossible happens.
throw new InternalError("Unexpected IllegalAccessException");
}
}
}
} finally {
unregister(lhs, rhs);
}
}
//-------------------------------------------------------------------------
/**
* Adds the result of super.equals() to this builder.
*
* @param superEquals the result of calling super.equals()
* @return EqualsBuilder - used to chain calls.
* @since 2.0
*/
public EqualsBuilder appendSuper(boolean superEquals) {
if (isEquals == false) {
return this;
}
isEquals = superEquals;
return this;
}
//-------------------------------------------------------------------------
/**
* Test if two Objects are equal using their
* equals method.
*
* @param lhs the left hand object
* @param rhs the right hand object
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(Object lhs, Object rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
Class lhsClass = lhs.getClass();
if (!lhsClass.isArray()) {
// The simple case, not an array, just test the element
isEquals = lhs.equals(rhs);
} else if (lhs.getClass() != rhs.getClass()) {
// Here when we compare different dimensions, for example: a boolean[][] to a boolean[]
this.setEquals(false);
}
// 'Switch' on type of array, to dispatch to the correct handler
// This handles multi dimensional arrays of the same depth
else if (lhs instanceof long[]) {
append((long[]) lhs, (long[]) rhs);
} else if (lhs instanceof int[]) {
append((int[]) lhs, (int[]) rhs);
} else if (lhs instanceof short[]) {
append((short[]) lhs, (short[]) rhs);
} else if (lhs instanceof char[]) {
append((char[]) lhs, (char[]) rhs);
} else if (lhs instanceof byte[]) {
append((byte[]) lhs, (byte[]) rhs);
} else if (lhs instanceof double[]) {
append((double[]) lhs, (double[]) rhs);
} else if (lhs instanceof float[]) {
append((float[]) lhs, (float[]) rhs);
} else if (lhs instanceof boolean[]) {
append((boolean[]) lhs, (boolean[]) rhs);
} else {
// Not an array of primitives
append((Object[]) lhs, (Object[]) rhs);
}
return this;
}
/**
*
* Test if two long s are equal.
*
*
* @param lhs
* the left hand long
* @param rhs
* the right hand long
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(long lhs, long rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two ints are equal.
*
* @param lhs the left hand int
* @param rhs the right hand int
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(int lhs, int rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two shorts are equal.
*
* @param lhs the left hand short
* @param rhs the right hand short
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(short lhs, short rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two chars are equal.
*
* @param lhs the left hand char
* @param rhs the right hand char
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(char lhs, char rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two bytes are equal.
*
* @param lhs the left hand byte
* @param rhs the right hand byte
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(byte lhs, byte rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two doubles are equal by testing that the
* pattern of bits returned by doubleToLong are equal.
*
* This handles NaNs, Infinities, and -0.0.
*
* It is compatible with the hash code generated by
* HashCodeBuilder.
*
* @param lhs the left hand double
* @param rhs the right hand double
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(double lhs, double rhs) {
if (isEquals == false) {
return this;
}
return append(Double.doubleToLongBits(lhs), Double.doubleToLongBits(rhs));
}
/**
* Test if two floats are equal byt testing that the
* pattern of bits returned by doubleToLong are equal.
*
* This handles NaNs, Infinities, and -0.0.
*
* It is compatible with the hash code generated by
* HashCodeBuilder.
*
* @param lhs the left hand float
* @param rhs the right hand float
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(float lhs, float rhs) {
if (isEquals == false) {
return this;
}
return append(Float.floatToIntBits(lhs), Float.floatToIntBits(rhs));
}
/**
* Test if two booleanss are equal.
*
* @param lhs the left hand boolean
* @param rhs the right hand boolean
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(boolean lhs, boolean rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Performs a deep comparison of two Object arrays.
*
* This also will be called for the top level of
* multi-dimensional, ragged, and multi-typed arrays.
*
* @param lhs the left hand Object[]
* @param rhs the right hand Object[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(Object[] lhs, Object[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of long. Length and all
* values are compared.
*
* The method {@link #append(long, long)} is used.
*
* @param lhs the left hand long[]
* @param rhs the right hand long[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(long[] lhs, long[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of int. Length and all
* values are compared.
*
* The method {@link #append(int, int)} is used.
*
* @param lhs the left hand int[]
* @param rhs the right hand int[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(int[] lhs, int[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of short. Length and all
* values are compared.
*
* The method {@link #append(short, short)} is used.
*
* @param lhs the left hand short[]
* @param rhs the right hand short[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(short[] lhs, short[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of char. Length and all
* values are compared.
*
* The method {@link #append(char, char)} is used.
*
* @param lhs the left hand char[]
* @param rhs the right hand char[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(char[] lhs, char[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of byte. Length and all
* values are compared.
*
* The method {@link #append(byte, byte)} is used.
*
* @param lhs the left hand byte[]
* @param rhs the right hand byte[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(byte[] lhs, byte[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of double. Length and all
* values are compared.
*
* The method {@link #append(double, double)} is used.
*
* @param lhs the left hand double[]
* @param rhs the right hand double[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(double[] lhs, double[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of float. Length and all
* values are compared.
*
* The method {@link #append(float, float)} is used.
*
* @param lhs the left hand float[]
* @param rhs the right hand float[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(float[] lhs, float[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Deep comparison of array of boolean. Length and all
* values are compared.
*
* The method {@link #append(boolean, boolean)} is used.
*
* @param lhs the left hand boolean[]
* @param rhs the right hand boolean[]
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(boolean[] lhs, boolean[] rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
this.setEquals(false);
return this;
}
if (lhs.length != rhs.length) {
this.setEquals(false);
return this;
}
for (int i = 0; i < lhs.length && isEquals; ++i) {
append(lhs[i], rhs[i]);
}
return this;
}
/**
* Returns true if the fields that have been checked
* are all equal.
*
* @return boolean
*/
public boolean isEquals() {
return this.isEquals;
}
/**
* Returns true if the fields that have been checked
* are all equal.
*
* @return true if all of the fields that have been checked
* are equal, false otherwise.
*
* @since 3.0
*/
public Boolean build() {
return Boolean.valueOf(isEquals());
}
/**
* Sets the isEquals value.
*
* @param isEquals The value to set.
* @since 2.1
*/
protected void setEquals(boolean isEquals) {
this.isEquals = isEquals;
}
/**
* Reset the EqualsBuilder so you can use the same object again
* @since 2.5
*/
public void reset() {
this.isEquals = true;
}
}