git-svn-id: https://svn.d4science.research-infrastructures.eu/gcube/trunk/data-analysis/EcologicalEngine@77251 82a268e6-3cf1-43bd-a215-b396298e98cf
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package org.gcube.dataanalysis.ecoengine.utils;
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import java.lang.reflect.AccessibleObject;
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import java.lang.reflect.Array;
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import java.lang.reflect.Field;
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import java.lang.reflect.Modifier;
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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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import org.gcube.dataanalysis.ecoengine.utils.LMEEnum.LMEEnumType;
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import sun.reflect.ConstructorAccessor;
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import sun.reflect.FieldAccessor;
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import sun.reflect.ReflectionFactory;
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public class DynamicEnum {
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private ReflectionFactory reflectionFactory = ReflectionFactory.getReflectionFactory();
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private void setFailsafeFieldValue(Field field, Object target, Object value) throws NoSuchFieldException,
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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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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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FieldAccessor fa = reflectionFactory.newFieldAccessor(field, false);
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fa.set(target, value);
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}
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private void blankField(Class<?> enumClass, String fieldName) throws NoSuchFieldException,
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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 void cleanEnumCache(Class<?> enumClass) 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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private ConstructorAccessor getConstructorAccessor(Class<?> enumClass, Class<?>[] additionalParameterTypes)
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throws NoSuchMethodException {
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Class<?>[] parameterTypes = new Class[additionalParameterTypes.length + 2];
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parameterTypes[0] = String.class;
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parameterTypes[1] = int.class;
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System.arraycopy(additionalParameterTypes, 0, parameterTypes, 2, additionalParameterTypes.length);
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return reflectionFactory.newConstructorAccessor(enumClass.getDeclaredConstructor(parameterTypes));
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}
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private Object makeEnum(Class<?> enumClass, String value, int ordinal, Class<?>[] additionalTypes,
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Object[] additionalValues) throws Exception {
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Object[] parms = new Object[additionalValues.length + 2];
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parms[0] = value;
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parms[1] = Integer.valueOf(ordinal);
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System.arraycopy(additionalValues, 0, parms, 2, additionalValues.length);
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return enumClass.cast(getConstructorAccessor(enumClass, additionalTypes).newInstance(parms));
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}
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/**
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* Add an enum instance to the enum class given as argument
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*
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* @param <T> the type of the enum (implicit)
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* @param enumType the class of the enum to be modified
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* @param enumName the name of the new enum instance to be added to the class.
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*/
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@SuppressWarnings("unchecked")
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public <T extends Enum<?>> void 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 "$VALUES" holder in enum class and get previous enum instances
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Field valuesField = null;
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Field[] fields = getFields();
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for (Field field : fields) {
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if (field.getName().contains("$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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List<T> values = new ArrayList<T>(Arrays.asList(previousValues));
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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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enumName, // THE NEW ENUM INSTANCE TO BE DYNAMICALLY ADDED
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values.size(),
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new Class<?>[] {}, // could be used to pass values to the enum constuctor if needed
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new Object[] {}); // could be used to pass values to the enum constuctor if needed
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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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setFailsafeFieldValue(valuesField, null, values.toArray((T[]) Array.newInstance(enumType, 0)));
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// 6. Clean enum cache
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cleanEnumCache(enumType);
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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 enum DynamicEnumE {
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};
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public Field[] getFields(){
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Field[] fields =DynamicEnumE.class.getDeclaredFields();
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return fields;
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}
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public static void main(String[] args) {
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DynamicEnum en = new DynamicEnum();
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// Dynamically add 3 new enum instances d, e, f to TestEnum
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en.addEnum(DynamicEnumE.class, "d");
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en.addEnum(DynamicEnumE.class, "e");
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en.addEnum(DynamicEnumE.class, "f");
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// Run a few tests just to show it works OK.
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System.out.println(Arrays.deepToString(DynamicEnumE.values()));
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// Shows : [a, b, c, d, e, f]
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}
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}
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@ -0,0 +1,37 @@
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package org.gcube.dataanalysis.ecoengine.utils;
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import java.lang.reflect.Field;
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import java.util.Arrays;
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public class LMEEnum extends DynamicEnum {
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public enum LMEEnumType {
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};
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public Field[] getFields() {
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Field[] fields = LMEEnumType.class.getDeclaredFields();
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return fields;
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}
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public static void main(String[] args) {
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LMEEnum en = new LMEEnum();
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en.addEnum(LMEEnumType.class, "CIAO");
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en.addEnum(LMEEnumType.class, "TEST");
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en.addEnum(LMEEnumType.class, "MIAO*_$");
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System.out.println(Arrays.deepToString(LMEEnumType.values()));
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/*
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DynamicEnum den = new DynamicEnum();
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den.addEnum(DynamicEnum.DynamicEnumE.class, "y");
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den.addEnum(DynamicEnum.DynamicEnumE.class, "r");
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den.addEnum(DynamicEnum.DynamicEnumE.class, "t");
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System.out.println(Arrays.deepToString(DynamicEnum.DynamicEnumE.values()));
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*/
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}
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}
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