// Copied from commons-lang
/*
* Copyright 2002-2005 The Apache Software Foundation.
*
* Licensed 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 com.w4t.ajax;
import java.lang.reflect.*;
import com.w4t.WebComponent;
import com.w4t.WebContainer;
/**
* <p>Assists in implementing {@link Object#hashCode()} methods.</p>
*
* <p> This class enables a good <code>hashCode</code> method to be built for any class. It
* follows the rules laid out in the book
* <a href="http://java.sun.com/docs/books/effective/index.html">Effective Java</a>
* by Joshua Bloch. Writing a good <code>hashCode</code> method is actually quite
* difficult. This class aims to simplify the process.</p>
*
* <p>All relevant fields from the object should be included in the
* <code>hashCode</code> method. Derived fields may be excluded. In general, any
* field used in the <code>equals</code> method must be used in the <code>hashCode</code>
* method.</p>
*
* <p>To use this class write code as follows:</p>
* <pre>
* public class Person {
* String name;
* int age;
* boolean isSmoker;
* ...
*
* public int hashCode() {
* // you pick a hard-coded, randomly chosen, non-zero, odd number
* // ideally different for each class
* return new HashCodeBuilder(17, 37).
* append(name).
* append(age).
* append(smoker).
* toHashCode();
* }
* }
* </pre>
*
* <p>If required, the superclass <code>hashCode()</code> can be added
* using {@link #appendSuper}.</p>
*
* <p>Alternatively, there is a method that uses reflection to determine
* the fields to test. Because these fields are usually private, the method,
* <code>reflectionHashCode</code>, uses <code>AccessibleObject.setAccessible</code> 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.</p>
*
* <p>A typical invocation for this method would look like:</p>
* <pre>
* public int hashCode() {
* return HashCodeBuilder.reflectionHashCode(this);
* }
* </pre>
*
* @author Stephen Colebourne
* @author Gary Gregory
* @author Pete Gieser
* @since 1.0
* @version $Id$
*/
final class HashCodeCalculator {
/**
* Constant to use in building the hashCode.
*/
private final int iConstant;
/**
* Running total of the hashCode.
*/
private int iTotal = 0;
/**
* <p>Uses two hard coded choices for the constants
* needed to build a <code>hashCode</code>.</p>
*/
public HashCodeCalculator() {
iConstant = 37;
iTotal = 17;
}
/**
* <p>Two randomly chosen, non-zero, odd numbers must be passed in.
* Ideally these should be different for each class, however this is
* not vital.</p>
*
* <p>Prime numbers are preferred, especially for the multiplier.</p>
*
* @param initialNonZeroOddNumber a non-zero, odd number used as the initial value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the multiplier
* @throws IllegalArgumentException if the number is zero or even
*/
public HashCodeCalculator(final int initialNonZeroOddNumber, final int multiplierNonZeroOddNumber) {
if (initialNonZeroOddNumber == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires a non zero initial value");
}
if (initialNonZeroOddNumber % 2 == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires an odd initial value");
}
if (multiplierNonZeroOddNumber == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires a non zero multiplier");
}
if (multiplierNonZeroOddNumber % 2 == 0) {
throw new IllegalArgumentException("HashCodeBuilder requires an odd multiplier");
}
iConstant = multiplierNonZeroOddNumber;
iTotal = initialNonZeroOddNumber;
}
//-------------------------------------------------------------------------
/**
* <p>This method uses reflection to build a valid hash code.</p>
*
* <p>This constructor uses two hard coded choices for the constants
* needed to build a hash code.</p>
*
* <p>It uses <code>AccessibleObject.setAccessible</code> 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.</p>
*
* <p>Transient members will be not be used, as they are likely derived
* fields, and not part of the value of the <code>Object</code>.</p>
*
* <p>Static fields will not be tested. Superclass fields will be included.</p>
*
* @param object the Object to create a <code>hashCode</code> for
* @return int hash code
* @throws IllegalArgumentException if the object is <code>null</code>
*/
public static int reflectionHashCode(final Object object) {
return reflectionHashCode(17, 37, object, false, null);
}
/**
* <p>This method uses reflection to build a valid hash code.</p>
*
* <p>This constructor uses two hard coded choices for the constants needed
* to build a hash code.</p>
*
* <p> It uses <code>AccessibleObject.setAccessible</code> 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.</p>
*
* <P>If the TestTransients parameter is set to <code>true</code>, 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</code>.</p>
*
* <p>Static fields will not be tested. Superclass fields will be included.</p>
*
* @param object the Object to create a <code>hashCode</code> for
* @param testTransients whether to include transient fields
* @return int hash code
* @throws IllegalArgumentException if the object is <code>null</code>
*/
public static int reflectionHashCode(final Object object, final boolean testTransients) {
return reflectionHashCode(17, 37, object, testTransients, null);
}
/**
* <p>This method uses reflection to build a valid hash code.</p>
*
* <p>It uses <code>AccessibleObject.setAccessible</code> 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.</p>
*
* <p>Transient members will be not be used, as they are likely derived
* fields, and not part of the value of the <code>Object</code>.</p>
*
* <p>Static fields will not be tested. Superclass fields will be included.</p>
*
* <p>Two randomly chosen, non-zero, odd numbers must be passed in. Ideally
* these should be different for each class, however this is not vital.
* Prime numbers are preferred, especially for the multiplier.</p>
*
* @param initialNonZeroOddNumber a non-zero, odd number used as the initial value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the multiplier
* @param object the Object to create a <code>hashCode</code> for
* @return int hash code
* @throws IllegalArgumentException if the Object is <code>null</code>
* @throws IllegalArgumentException if the number is zero or even
*/
public static int reflectionHashCode(
final int initialNonZeroOddNumber, final int multiplierNonZeroOddNumber, final Object object) {
return reflectionHashCode(initialNonZeroOddNumber, multiplierNonZeroOddNumber, object, false, null);
}
/**
* <p>This method uses reflection to build a valid hash code.</p>
*
* <p>It uses <code>AccessibleObject.setAccessible</code> 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.</p>
*
* <p>If the TestTransients parameter is set to <code>true</code>, 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</code>.</p>
*
* <p>Static fields will not be tested. Superclass fields will be included.</p>
*
* <p>Two randomly chosen, non-zero, odd numbers must be passed in. Ideally
* these should be different for each class, however this is not vital.
* Prime numbers are preferred, especially for the multiplier.</p>
*
* @param initialNonZeroOddNumber a non-zero, odd number used as the initial value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the multiplier
* @param object the Object to create a <code>hashCode</code> for
* @param testTransients whether to include transient fields
* @return int hash code
* @throws IllegalArgumentException if the Object is <code>null</code>
* @throws IllegalArgumentException if the number is zero or even
*/
public static int reflectionHashCode(
final int initialNonZeroOddNumber, final int multiplierNonZeroOddNumber,
final Object object, final boolean testTransients) {
return reflectionHashCode(initialNonZeroOddNumber, multiplierNonZeroOddNumber, object, testTransients, null);
}
/**
* <p>This method uses reflection to build a valid hash code.</p>
*
* <p>It uses <code>AccessibleObject.setAccessible</code> 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.</p>
*
* <p>If the TestTransients parameter is set to <code>true</code>, 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</code>.</p>
*
* <p>Static fields will not be included. Superclass fields will be included
* up to and including the specified superclass. A null superclass is treated
* as java.lang.Object.</p>
*
* <p>Two randomly chosen, non-zero, odd numbers must be passed in. Ideally
* these should be different for each class, however this is not vital.
* Prime numbers are preferred, especially for the multiplier.</p>
*
* @param initialNonZeroOddNumber a non-zero, odd number used as the initial value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the multiplier
* @param object the Object to create a <code>hashCode</code> for
* @param testTransients whether to include transient fields
* @param reflectUpToClass the superclass to reflect up to (inclusive),
* may be <code>null</code>
* @return int hash code
* @throws IllegalArgumentException if the Object is <code>null</code>
* @throws IllegalArgumentException if the number is zero or even
* @since 2.0
*/
public static int reflectionHashCode(
final int initialNonZeroOddNumber,
final int multiplierNonZeroOddNumber,
final Object object,
final boolean testTransients,
final Class reflectUpToClass) {
if (object == null) {
throw new IllegalArgumentException("The object to build a hash code for must not be null");
}
HashCodeCalculator builder = new HashCodeCalculator(initialNonZeroOddNumber, multiplierNonZeroOddNumber);
Class clazz = object.getClass();
reflectionAppend(object, clazz, builder, testTransients);
while (clazz.getSuperclass() != null && clazz != reflectUpToClass) {
clazz = clazz.getSuperclass();
reflectionAppend(object, clazz, builder, testTransients);
}
return builder.toHashCode();
}
/**
* <p>Appends the fields and values defined by the given object of the
* given <code>Class</code>.</p>
*
* @param object the object to append details of
* @param clazz the class to append details of
* @param builder the builder to append to
* @param useTransients whether to use transient fields
*/
private static void reflectionAppend(final Object object, final Class clazz, final HashCodeCalculator builder, final boolean useTransients) {
Field[] fields = clazz.getDeclaredFields();
AccessibleObject.setAccessible(fields, true);
for (int i = 0; i < fields.length; i++) {
Field f = fields[i];
if ((f.getName().indexOf('$') == -1)
&& (useTransients || !Modifier.isTransient(f.getModifiers()))
&& (!Modifier.isStatic(f.getModifiers()))) {
try {
builder.append(f.get(object));
} 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");
}
}
}
}
//-------------------------------------------------------------------------
/**
* <p>Adds the result of super.hashCode() to this builder.</p>
*
* @param superHashCode the result of calling <code>super.hashCode()</code>
* @return this HashCodeBuilder, used to chain calls.
* @since 2.0
*/
public HashCodeCalculator appendSuper(final int superHashCode) {
iTotal = iTotal * iConstant + superHashCode;
return this;
}
//-------------------------------------------------------------------------
/**
* <p>Append a <code>hashCode</code> for an <code>Object</code>.</p>
*
* @param object the Object to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final Object object) {
if (object == null) {
iTotal = iTotal * iConstant;
} else {
if (object.getClass().isArray() == false) {
//the simple case, not an array, just the element
iTotal = iTotal * iConstant + object.hashCode();
} else {
//'Switch' on type of array, to dispatch to the correct handler
// This handles multi dimensional arrays
if (object instanceof long[]) {
append((long[]) object);
} else if (object instanceof int[]) {
append((int[]) object);
} else if (object instanceof short[]) {
append((short[]) object);
} else if (object instanceof char[]) {
append((char[]) object);
} else if (object instanceof byte[]) {
append((byte[]) object);
} else if (object instanceof double[]) {
append((double[]) object);
} else if (object instanceof float[]) {
append((float[]) object);
} else if (object instanceof boolean[]) {
append((boolean[]) object);
} else {
// Not an array of primitives
append((Object[]) object);
}
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>long</code>.</p>
*
* @param value the long to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final long value) {
iTotal = iTotal * iConstant + ((int) (value ^ (value >> 32)));
return this;
}
/**
* <p>Append a <code>hashCode</code> for an <code>int</code>.</p>
*
* @param value the int to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final int value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>short</code>.</p>
*
* @param value the short to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final short value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>char</code>.</p>
*
* @param value the char to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final char value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>byte</code>.</p>
*
* @param value the byte to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final byte value) {
iTotal = iTotal * iConstant + value;
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>double</code>.</p>
*
* @param value the double to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final double value) {
return append(Double.doubleToLongBits(value));
}
/**
* <p>Append a <code>hashCode</code> for a <code>float</code>.</p>
*
* @param value the float to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final float value) {
iTotal = iTotal * iConstant + Float.floatToIntBits(value);
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>boolean</code>.</p>
* <p>This adds <code>iConstant * 1</code> to the <code>hashCode</code>
* and not a <code>1231</code> or <code>1237</code> as done in java.lang.Boolean.
* This is in accordance with the <quote>Effective Java</quote> design. </p>
*
* @param value the boolean to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final boolean value) {
iTotal = iTotal * iConstant + (value ? 0 : 1);
return this;
}
/**
* <p>Append a <code>hashCode</code> for an <code>Object</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final Object[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
public HashCodeCalculator append( final WebContainer container ) {
if( container.getWebComponentCount() == 0 ) {
iTotal = iTotal * iConstant;
} else {
for( int i = 0; i < container.getWebComponentCount(); i++ ) {
WebComponent component = container.get( i );
append( component );
Object constraint = container.getConstraint( component );
if( constraint != null ) {
append( constraint );
}
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>long</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final long[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for an <code>int</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final int[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>short</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final short[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>char</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final char[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>byte</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final byte[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>double</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final double[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>float</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final float[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Append a <code>hashCode</code> for a <code>boolean</code> array.</p>
*
* @param array the array to add to the <code>hashCode</code>
* @return this
*/
public HashCodeCalculator append(final boolean[] array) {
if (array == null) {
iTotal = iTotal * iConstant;
} else {
for (int i = 0; i < array.length; i++) {
append(array[i]);
}
}
return this;
}
/**
* <p>Return the computed <code>hashCode</code>.</p>
*
* @return <code>hashCode</code> based on the fields appended
*/
public int toHashCode() {
return iTotal;
}
}