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com.anwen.mongo.toolkit.builder.CompareToBuilder Maven / Gradle / Ivy
package com.anwen.mongo.toolkit.builder;
import com.anwen.mongo.toolkit.ArrayUtils;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.List;
/**
* 协助实现Comparable.compareTo(Object)方法。
* 它与EqualsBuilder和HashCodeBuilder构建的equals(Object)和hashcode()一致。
* 使用equals(Object)比较相等的两个对象通常也应使用compareTo(Object)进行相等比较。
* 所有相关字段都应包括在比较的计算中。派生字段可能会被忽略。compareTo(Object)和equals(Object)中应以相同的顺序使用相同的字段。
* 要使用此类,请编写以下代码:
* 公共类MyClass{
* 字符串字段1;
* int字段2;
* 布尔字段3;
* ...
* public int compareTo(对象o){
* MyClass MyClass=(MyClass)o;
* 返回new CompareToBuilder()
* .appendSuper(super.compareTo(o)
* .append(this.field1,myClass.field1)
* .append(this.field2,myClass.field2)
* .append(this.field3,myClass.field3)
* .toComparison();
* }
* }
* 或者,也有使用反射的reflectionCompare方法
* @author JiaChaoYang
**/
public class CompareToBuilder implements Builder {
/**
* Current state of the comparison as appended fields are checked.
*/
private int comparison;
/**
* Constructor for CompareToBuilder.
*
* Starts off assuming that the objects are equal. Multiple calls are
* then made to the various append methods, followed by a call to
* {@link #toComparison} to get the result.
*/
public CompareToBuilder() {
super();
comparison = 0;
}
//-----------------------------------------------------------------------
/**
* Compares two Object
s via reflection.
*
* Fields can be private, thus AccessibleObject.setAccessible
* is used to bypass normal access control checks. This will fail under a
* security manager unless the appropriate permissions are set.
*
*
* - Static fields will not be compared
* - Transient members will be not be compared, as they are likely derived
* fields
* - Superclass fields will be compared
*
*
* If both lhs
and rhs
are null
,
* they are considered equal.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @return a negative integer, zero, or a positive integer as lhs
* is less than, equal to, or greater than rhs
* @throws NullPointerException if either (but not both) parameters are
* null
* @throws ClassCastException if rhs
is not assignment-compatible
* with lhs
*/
public static int reflectionCompare(final Object lhs, final Object rhs) {
return reflectionCompare(lhs, rhs, false, null);
}
/**
* Compares two Object
s via reflection.
*
* Fields can be private, thus AccessibleObject.setAccessible
* is used to bypass normal access control checks. This will fail under a
* security manager unless the appropriate permissions are set.
*
*
* - Static fields will not be compared
* - If
compareTransients
is true
,
* compares transient members. Otherwise ignores them, as they
* are likely derived fields.
* - Superclass fields will be compared
*
*
* If both lhs
and rhs
are null
,
* they are considered equal.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @param compareTransients whether to compare transient fields
* @return a negative integer, zero, or a positive integer as lhs
* is less than, equal to, or greater than rhs
* @throws NullPointerException if either lhs
or rhs
* (but not both) is null
* @throws ClassCastException if rhs
is not assignment-compatible
* with lhs
*/
public static int reflectionCompare(final Object lhs, final Object rhs, final boolean compareTransients) {
return reflectionCompare(lhs, rhs, compareTransients, null);
}
/**
* Compares two Object
s via reflection.
*
* Fields can be private, thus AccessibleObject.setAccessible
* is used to bypass normal access control checks. This will fail under a
* security manager unless the appropriate permissions are set.
*
*
* - Static fields will not be compared
* - If
compareTransients
is true
,
* compares transient members. Otherwise ignores them, as they
* are likely derived fields.
* - Superclass fields will be compared
*
*
* If both lhs
and rhs
are null
,
* they are considered equal.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @param excludeFields Collection of String fields to exclude
* @return a negative integer, zero, or a positive integer as lhs
* is less than, equal to, or greater than rhs
* @throws NullPointerException if either lhs
or rhs
* (but not both) is null
* @throws ClassCastException if rhs
is not assignment-compatible
* with lhs
* @since 2.2
*/
public static int reflectionCompare(final Object lhs, final Object rhs, final Collection excludeFields) {
return reflectionCompare(lhs, rhs, toNoNullStringArray(excludeFields));
}
/**
* Compares two Object
s via reflection.
*
* Fields can be private, thus AccessibleObject.setAccessible
* is used to bypass normal access control checks. This will fail under a
* security manager unless the appropriate permissions are set.
*
*
* - Static fields will not be compared
* - If
compareTransients
is true
,
* compares transient members. Otherwise ignores them, as they
* are likely derived fields.
* - Superclass fields will be compared
*
*
* If both lhs
and rhs
are null
,
* they are considered equal.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @param excludeFields array of fields to exclude
* @return a negative integer, zero, or a positive integer as lhs
* is less than, equal to, or greater than rhs
* @throws NullPointerException if either lhs
or rhs
* (but not both) is null
* @throws ClassCastException if rhs
is not assignment-compatible
* with lhs
* @since 2.2
*/
public static int reflectionCompare(final Object lhs, final Object rhs, final String... excludeFields) {
return reflectionCompare(lhs, rhs, false, null, excludeFields);
}
/**
* Compares two Object
s via reflection.
*
* Fields can be private, thus AccessibleObject.setAccessible
* is used to bypass normal access control checks. This will fail under a
* security manager unless the appropriate permissions are set.
*
*
* - Static fields will not be compared
* - If the
compareTransients
is true
,
* compares transient members. Otherwise ignores them, as they
* are likely derived fields.
* - Compares superclass fields up to and including
reflectUpToClass
.
* If reflectUpToClass
is null
, compares all superclass fields.
*
*
* If both lhs
and rhs
are null
,
* they are considered equal.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @param compareTransients whether to compare transient fields
* @param reflectUpToClass last superclass for which fields are compared
* @param excludeFields fields to exclude
* @return a negative integer, zero, or a positive integer as lhs
* is less than, equal to, or greater than rhs
* @throws NullPointerException if either lhs
or rhs
* (but not both) is null
* @throws ClassCastException if rhs
is not assignment-compatible
* with lhs
* @since 2.2 (2.0 as reflectionCompare(Object, Object, boolean, Class)
)
*/
public static int reflectionCompare(
final Object lhs,
final Object rhs,
final boolean compareTransients,
final Class> reflectUpToClass,
final String... excludeFields) {
if (lhs == rhs) {
return 0;
}
if (lhs == null || rhs == null) {
throw new NullPointerException();
}
Class> lhsClazz = lhs.getClass();
if (!lhsClazz.isInstance(rhs)) {
throw new ClassCastException();
}
final CompareToBuilder compareToBuilder = new CompareToBuilder();
reflectionAppend(lhs, rhs, lhsClazz, compareToBuilder, compareTransients, excludeFields);
while (lhsClazz.getSuperclass() != null && lhsClazz != reflectUpToClass) {
lhsClazz = lhsClazz.getSuperclass();
reflectionAppend(lhs, rhs, lhsClazz, compareToBuilder, compareTransients, excludeFields);
}
return compareToBuilder.toComparison();
}
/**
* Appends to builder
the comparison of lhs
* to rhs
using the fields defined in clazz
.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @param clazz Class
that defines fields to be compared
* @param builder CompareToBuilder
to append to
* @param useTransients whether to compare transient fields
* @param excludeFields fields to exclude
*/
private static void reflectionAppend(
final Object lhs,
final Object rhs,
final Class> clazz,
final CompareToBuilder builder,
final boolean useTransients,
final String[] excludeFields) {
final Field[] fields = clazz.getDeclaredFields();
AccessibleObject.setAccessible(fields, true);
for (int i = 0; i < fields.length && builder.comparison == 0; i++) {
final 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 (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");
}
}
}
}
//-----------------------------------------------------------------------
/**
* Appends to the builder
the compareTo(Object)
* result of the superclass.
*
* @param superCompareTo result of calling super.compareTo(Object)
* @return this - used to chain append calls
* @since 2.0
*/
public CompareToBuilder appendSuper(final int superCompareTo) {
if (comparison != 0) {
return this;
}
comparison = superCompareTo;
return this;
}
//-----------------------------------------------------------------------
/**
* Appends to the builder
the comparison of
* two Object
s.
*
*
* - Check if
lhs == rhs
* - Check if either
lhs
or rhs
is null
,
* a null
object is less than a non-null
object
* - Check the object contents
*
*
* lhs
must either be an array or implement {@link Comparable}.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @return this - used to chain append calls
* @throws ClassCastException if rhs
is not assignment-compatible
* with lhs
*/
public CompareToBuilder append(final Object lhs, final Object rhs) {
return append(lhs, rhs, null);
}
/**
* Appends to the builder
the comparison of
* two Object
s.
*
*
* - Check if
lhs == rhs
* - Check if either
lhs
or rhs
is null
,
* a null
object is less than a non-null
object
* - Check the object contents
*
*
* If lhs
is an array, array comparison methods will be used.
* Otherwise comparator
will be used to compare the objects.
* If comparator
is null
, lhs
must
* implement {@link Comparable} instead.
*
* @param lhs left-hand object
* @param rhs right-hand object
* @param comparator Comparator
used to compare the objects,
* null
means treat lhs as Comparable
* @return this - used to chain append calls
* @throws ClassCastException if rhs
is not assignment-compatible
* with lhs
* @since 2.0
*/
public CompareToBuilder append(final Object lhs, final Object rhs, final Comparator> comparator) {
if (comparison != 0) {
return this;
}
if (lhs == rhs) {
return this;
}
if (lhs == null) {
comparison = -1;
return this;
}
if (rhs == null) {
comparison = +1;
return this;
}
if (lhs.getClass().isArray()) {
// switch on type of array, to dispatch to the correct handler
// handles multi dimensional arrays
// throws a ClassCastException if rhs is not the correct array type
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
// throws a ClassCastException if rhs is not an array
append((Object[]) lhs, (Object[]) rhs, comparator);
}
} else {
// the simple case, not an array, just test the element
if (comparator == null) {
@SuppressWarnings("unchecked") // assume this can be done; if not throw CCE as per Javadoc
final Comparable