com.jchanghong.core.builder.CompareToBuilder Maven / Gradle / Ivy
package com.jchanghong.core.builder;
import com.jchanghong.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.Comparator;
/**
* 用于构建 {@link java.lang.Comparable#compareTo(Object)} 方法的辅助工具
*
*
* 在Bean对象中，所有相关字段都参与比对，继承的字段不参与。使用方法如下：
*
*
* public class MyClass {
* String field1;
* int field2;
* boolean field3;
*
* ...
*
* public int compareTo(Object o) {
* MyClass myClass = (MyClass) o;
* return new CompareToBuilder()
* .appendSuper(super.compareTo(o)
* .append(this.field1, myClass.field1)
* .append(this.field2, myClass.field2)
* .append(this.field3, myClass.field3)
* .toComparison();
* }
* }
*
*
* 字段值按照顺序比较，如果某个字段返回非0结果，比较终止，使用{@code toComparison()}返回结果，后续比较忽略。
*
*
* 也可以使用{@link #reflectionCompare(Object, Object) reflectionCompare} 方法通过反射比较字段，使用方法如下：
*
*
* public int compareTo(Object o) {
* return CompareToBuilder.reflectionCompare(this, o);
* }
*
*
*TODO 待整理
* 来自于Apache-Commons-Lang3
* @author looly，Apache-Commons
* @since 4.2.2
*/
public class CompareToBuilder implements Builder {
private static final long serialVersionUID = 1L;
/** 当前比较状态 */
private int comparison;
/**
* 构造，构造后调用append方法增加比较项，然后调用{@link #toComparison()}获取结果
*/
public CompareToBuilder() {
super();
comparison = 0;
}
//-----------------------------------------------------------------------
/**
* 通过反射比较两个Bean对象，对象字段可以为private。比较规则如下：
*
*
* - static字段不比较
* - Transient字段不参与比较
* - 父类字段参与比较
*
*
*
*如果被比较的两个对象都为null，被认为相同。
*
* @param lhs 第一个对象
* @param rhs 第二个对象
* @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 Objects 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 Objects 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, ArrayUtil.toArray(excludeFields, String.class));
}
/**
* Compares two Objects 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 Objects 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 (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");
}
}
}
}
//-----------------------------------------------------------------------
/**
* 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 Objects.
*
*
* - 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 Objects.
*
*
* - 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