cn.hutool.core.builder.EqualsBuilder Maven / Gradle / Ivy
package cn.hutool.core.builder;
import cn.hutool.core.lang.Pair;
import cn.hutool.core.util.ArrayUtil;
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;
/**
* {@link Object#equals(Object)} 方法的构建器
*
* 两个对象equals必须保证hashCode值相等，hashCode值相等不能保证一定equals
*
* 使用方法如下：
*
* 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();
* }
*
*
* 我们也可以通过反射判断所有字段是否equals：
*
* public boolean equals(Object obj) {
* return EqualsBuilder.reflectionEquals(this, obj);
* }
*
*
* 来自Apache Commons Lang改造
*/
public class EqualsBuilder implements Builder {
private static final long serialVersionUID = 1L;
/**
*
* A registry of objects used by reflection methods to detect cyclical object references and avoid infinite loops.
*
*/
private static final ThreadLocal>> REGISTRY = new ThreadLocal<>();
/**
*
* 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 {@code this} object
* @param rhs the other object
* @return the pair
*/
static Pair getRegisterPair(final Object lhs, final Object rhs) {
final IDKey left = new IDKey(lhs);
final IDKey right = new IDKey(rhs);
return new Pair<>(left, right);
}
/**
*
* Returns {@code 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 {@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.
* @since 3.0
*/
static boolean isRegistered(final Object lhs, final Object rhs) {
final Set> registry = getRegistry();
final Pair pair = getRegisterPair(lhs, rhs);
final Pair swappedPair = new Pair<>(pair.getKey(), pair.getValue());
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 {@code this} object to register
* @param rhs the other object to register
*/
static void register(final Object lhs, final Object rhs) {
synchronized (EqualsBuilder.class) {
if (getRegistry() == null) {
REGISTRY.set(new HashSet<>());
}
}
final Set> registry = getRegistry();
final Pair pair = getRegisterPair(lhs, rhs);
registry.add(pair);
}
/**
*
* Unregisters the given object pair.
*
*
*
* Used by the reflection methods to avoid infinite loops.
*
* @param lhs {@code this} object to unregister
* @param rhs the other object to unregister
* @since 3.0
*/
static void unregister(final Object lhs, final Object rhs) {
Set> registry = getRegistry();
if (registry != null) {
final Pair pair = getRegisterPair(lhs, rhs);
registry.remove(pair);
synchronized (EqualsBuilder.class) {
//read again
registry = getRegistry();
if (registry != null && registry.isEmpty()) {
REGISTRY.remove();
}
}
}
}
/**
* 是否equals，此值随着构建会变更，默认true
*/
private boolean isEquals = true;
/**
* 构造，初始状态值为true
*/
public EqualsBuilder() {
// do nothing for now.
}
//-------------------------------------------------------------------------
/**
* 反射检查两个对象是否equals，此方法检查对象及其父对象的属性（包括私有属性）是否equals
*
* @param lhs 此对象
* @param rhs 另一个对象
* @param excludeFields 排除的字段集合，如果有不参与计算equals的字段加入此集合即可
* @return 两个对象是否equals，是返回{@code true}
*/
public static boolean reflectionEquals(final Object lhs, final Object rhs, final Collection excludeFields) {
return reflectionEquals(lhs, rhs, ArrayUtil.toArray(excludeFields, String.class));
}
/**
* 反射检查两个对象是否equals，此方法检查对象及其父对象的属性（包括私有属性）是否equals
*
* @param lhs 此对象
* @param rhs 另一个对象
* @param excludeFields 排除的字段集合，如果有不参与计算equals的字段加入此集合即可
* @return 两个对象是否equals，是返回{@code true}
*/
public static boolean reflectionEquals(final Object lhs, final Object rhs, final String... excludeFields) {
return reflectionEquals(lhs, rhs, false, null, excludeFields);
}
/**
* This method uses reflection to determine if the two {@code Object}s
* are equal.
*
* It uses {@code 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. Non-primitive fields are compared using
* {@code equals()}.
*
* If the TestTransients parameter is set to {@code true}, transient
* members will be tested, otherwise they are ignored, as they are likely
* derived fields, and not part of the value of the {@code Object}.
*
* Static fields will not be tested. Superclass fields will be included.
*
* @param lhs {@code this} object
* @param rhs the other object
* @param testTransients whether to include transient fields
* @return {@code true} if the two Objects have tested equals.
*/
public static boolean reflectionEquals(final Object lhs, final Object rhs, final boolean testTransients) {
return reflectionEquals(lhs, rhs, testTransients, null);
}
/**
* This method uses reflection to determine if the two {@code Object}s
* are equal.
*
* It uses {@code 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. Non-primitive fields are compared using
* {@code equals()}.
*
* If the testTransients parameter is set to {@code true}, transient
* members will be tested, otherwise they are ignored, as they are likely
* derived fields, and not part of the value of the {@code 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 {@code 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 {@code null}
* @param excludeFields array of field names to exclude from testing
* @return {@code true} if the two Objects have tested equals.
* @since 2.0
*/
public static boolean reflectionEquals(final Object lhs, final Object rhs, final boolean testTransients, final Class reflectUpToClass,
final 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.
final Class lhsClass = lhs.getClass();
final 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;
}
final EqualsBuilder equalsBuilder = new EqualsBuilder();
try {
if (testClass.isArray()) {
equalsBuilder.append(lhs, rhs);
} else {
reflectionAppend(lhs, rhs, testClass, equalsBuilder, testTransients, excludeFields);
while (testClass.getSuperclass() != null && testClass != reflectUpToClass) {
testClass = testClass.getSuperclass();
reflectionAppend(lhs, rhs, testClass, equalsBuilder, testTransients, excludeFields);
}
}
} catch (final 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(
final Object lhs,
final Object rhs,
final Class clazz,
final EqualsBuilder builder,
final boolean useTransients,
final String[] excludeFields) {
if (isRegistered(lhs, rhs)) {
return;
}
try {
register(lhs, rhs);
final Field[] fields = clazz.getDeclaredFields();
AccessibleObject.setAccessible(fields, true);
for (int i = 0; i < fields.length && builder.isEquals; i++) {
final Field f = fields[i];
if (false == ArrayUtil.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 (final 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 {@code super.equals()} to this builder.
*
* @param superEquals the result of calling {@code super.equals()}
* @return EqualsBuilder - used to chain calls.
* @since 2.0
*/
public EqualsBuilder appendSuper(final boolean superEquals) {
if (isEquals == false) {
return this;
}
isEquals = superEquals;
return this;
}
//-------------------------------------------------------------------------
/**
* Test if two {@code Object}s are equal using their
* {@code equals} method.
*
* @param lhs the left hand object
* @param rhs the right hand object
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final Object lhs, final Object rhs) {
if (isEquals == false) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null || rhs == null) {
return setEquals(false);
}
if (ArrayUtil.isArray(lhs)) {
// 判断数组的equals
return setEquals(ArrayUtil.equals(lhs, rhs));
}
// The simple case, not an array, just test the element
return setEquals(lhs.equals(rhs));
}
/**
*
* Test if two {@code long} s are equal.
*
*
* @param lhs the left hand {@code long}
* @param rhs the right hand {@code long}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final long lhs, final long rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two {@code int}s are equal.
*
* @param lhs the left hand {@code int}
* @param rhs the right hand {@code int}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final int lhs, final int rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two {@code short}s are equal.
*
* @param lhs the left hand {@code short}
* @param rhs the right hand {@code short}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final short lhs, final short rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two {@code char}s are equal.
*
* @param lhs the left hand {@code char}
* @param rhs the right hand {@code char}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final char lhs, final char rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two {@code byte}s are equal.
*
* @param lhs the left hand {@code byte}
* @param rhs the right hand {@code byte}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final byte lhs, final byte rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Test if two {@code double}s are equal by testing that the
* pattern of bits returned by {@code doubleToLong} are equal.
*
* This handles NaNs, Infinities, and {@code -0.0}.
*
* It is compatible with the hash code generated by
* {@code HashCodeBuilder}.
*
* @param lhs the left hand {@code double}
* @param rhs the right hand {@code double}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final double lhs, final double rhs) {
if (isEquals == false) {
return this;
}
return append(Double.doubleToLongBits(lhs), Double.doubleToLongBits(rhs));
}
/**
* Test if two {@code float}s are equal byt testing that the
* pattern of bits returned by doubleToLong are equal.
*
* This handles NaNs, Infinities, and {@code -0.0}.
*
* It is compatible with the hash code generated by
* {@code HashCodeBuilder}.
*
* @param lhs the left hand {@code float}
* @param rhs the right hand {@code float}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final float lhs, final float rhs) {
if (isEquals == false) {
return this;
}
return append(Float.floatToIntBits(lhs), Float.floatToIntBits(rhs));
}
/**
* Test if two {@code booleans}s are equal.
*
* @param lhs the left hand {@code boolean}
* @param rhs the right hand {@code boolean}
* @return EqualsBuilder - used to chain calls.
*/
public EqualsBuilder append(final boolean lhs, final boolean rhs) {
if (isEquals == false) {
return this;
}
isEquals = (lhs == rhs);
return this;
}
/**
* Returns {@code true} if the fields that have been checked
* are all equal.
*
* @return boolean
*/
public boolean isEquals() {
return this.isEquals;
}
/**
* Returns {@code true} if the fields that have been checked
* are all equal.
*
* @return {@code true} if all of the fields that have been checked
* are equal, {@code false} otherwise.
* @since 3.0
*/
@Override
public Boolean build() {
return isEquals();
}
/**
* Sets the {@code isEquals} value.
*
* @param isEquals The value to set.
* @return this
*/
protected EqualsBuilder setEquals(boolean isEquals) {
this.isEquals = isEquals;
return this;
}
/**
* Reset the EqualsBuilder so you can use the same object again
*
* @since 2.5
*/
public void reset() {
this.isEquals = true;
}
}