2018-08-16 09:56:31 +00:00
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package com.boydti.fawe.util;
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import sun.misc.Unsafe;
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2019-06-12 13:45:41 +00:00
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import java.lang.reflect.*;
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2018-08-16 09:56:31 +00:00
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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public class ReflectionUtils9 {
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public static <T extends Enum<?>> T addEnum(Class<T> enumType, String enumName) {
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// 0. Sanity checks
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if (!Enum.class.isAssignableFrom(enumType)) {
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throw new RuntimeException("class " + enumType + " is not an instance of Enum");
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}
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// 1. Lookup "$VALUES" holder in enum class and get previous enum instances
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Field valuesField = null;
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Field[] fields = enumType.getDeclaredFields();
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for (Field field : fields) {
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if (field.getName().contains("$VALUES")) {
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valuesField = field;
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break;
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}
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}
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AccessibleObject.setAccessible(new Field[]{valuesField}, true);
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try {
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// 2. Copy it
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T[] previousValues = (T[]) valuesField.get(enumType);
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2019-06-12 21:12:12 +00:00
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List values = new ArrayList<>(Arrays.asList(previousValues));
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2018-08-16 09:56:31 +00:00
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// 3. build new enum
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T newValue = (T) makeEnum(enumType, // The target enum class
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2019-06-12 13:45:41 +00:00
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enumName, // THE NEW ENUM INSTANCE TO BE DYNAMICALLY ADDED
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values.size()); // can be used to pass values to the enum constuctor
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2018-08-16 09:56:31 +00:00
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// 4. add new value
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values.add(newValue);
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// 5. Set new values field
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try {
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setFailsafeFieldValue(valuesField, null,
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2019-06-12 13:45:41 +00:00
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values.toArray((T[]) Array.newInstance(enumType, 0)));
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2018-08-16 09:56:31 +00:00
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} catch (Throwable e) {
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Field ordinalField = Enum.class.getDeclaredField("ordinal");
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setFailsafeFieldValue(ordinalField, newValue, 0);
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}
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// 6. Clean enum cache
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cleanEnumCache(enumType);
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return newValue;
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} catch (Exception e) {
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e.printStackTrace();
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throw new RuntimeException(e.getMessage(), e);
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}
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}
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public static Object makeEnum(Class<?> enumClass, String value, int ordinal) throws Exception {
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Constructor<?> constructor = Unsafe.class.getDeclaredConstructors()[0];
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constructor.setAccessible(true);
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Unsafe unsafe = (Unsafe) constructor.newInstance();
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Object instance = unsafe.allocateInstance(enumClass);
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Field ordinalField = Enum.class.getDeclaredField("ordinal");
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setFailsafeFieldValue(ordinalField, instance, 0);
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Field nameField = Enum.class.getDeclaredField("name");
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setFailsafeFieldValue(nameField, instance, value);
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return instance;
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}
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public static void setFailsafeFieldValue(Field field, Object target, Object value)
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throws NoSuchFieldException, IllegalAccessException {
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// let's make the field accessible
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field.setAccessible(true);
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// next we change the modifier in the Field instance to
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// not be final anymore, thus tricking reflection into
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// letting us modify the static final field
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if (Modifier.isFinal(field.getModifiers())) {
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Field modifiersField = Field.class.getDeclaredField("modifiers");
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modifiersField.setAccessible(true);
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int modifiers = modifiersField.getInt(field);
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// blank out the final bit in the modifiers int
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modifiers &= ~Modifier.FINAL;
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modifiersField.setInt(field, modifiers);
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}
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try {
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2019-06-12 13:45:41 +00:00
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if (target == null) field.set(null, value);
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else field.set(target, value);
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2018-08-16 09:56:31 +00:00
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} catch (NoSuchMethodError error) {
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field.set(target, value);
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}
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}
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private static void blankField(Class<?> enumClass, String fieldName)
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throws NoSuchFieldException, IllegalAccessException {
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for (Field field : Class.class.getDeclaredFields()) {
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if (field.getName().contains(fieldName)) {
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AccessibleObject.setAccessible(new Field[]{field}, true);
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setFailsafeFieldValue(field, enumClass, null);
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break;
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}
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}
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}
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private static void cleanEnumCache(Class<?> enumClass)
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throws NoSuchFieldException, IllegalAccessException {
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blankField(enumClass, "enumConstantDirectory"); // Sun (Oracle?!?) JDK 1.5/6
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blankField(enumClass, "enumConstants"); // IBM JDK
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}
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}
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