首页新闻找找看学习计划

java动态生成枚举类

0
悬赏园豆:10 [已解决问题] 解决于 2019-09-10 16:36

一下是网上copy得util 可以直接使用 需要的可以直接拿走
但是我有个问题 就是下面代码得枚举类是连个参数的 可我的是5个参数得 我知道makeEnum和addEnum两个方法需要改一下 但是没看懂不知道怎么改 请大佬帮着看看指点指点

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import sun.reflect.ConstructorAccessor;
import sun.reflect.FieldAccessor;
import sun.reflect.ReflectionFactory;

public class DynamicEnumUtil {

private static ReflectionFactory reflectionFactory = ReflectionFactory.getReflectionFactory();

private static void setFailsafeFieldValue(Field field, Object target, Object value) throws NoSuchFieldException,
IllegalAccessException {

   // let's make the field accessible
   field.setAccessible(true);

   // next we change the modifier in the Field instance to
   // not be final anymore, thus tricking reflection into
   // letting us modify the static final field
   Field modifiersField = Field.class.getDeclaredField("modifiers");
   modifiersField.setAccessible(true);
   int modifiers = modifiersField.getInt(field);

   // blank out the final bit in the modifiers int
   modifiers &= ~Modifier.FINAL;
   modifiersField.setInt(field, modifiers);

   FieldAccessor fa = reflectionFactory.newFieldAccessor(field, false);
   fa.set(target, value);

}

private static void blankField(Class<?> enumClass, String fieldName) throws NoSuchFieldException,
IllegalAccessException {
for (Field field : Class.class.getDeclaredFields()) {
if (field.getName().contains(fieldName)) {
AccessibleObject.setAccessible(new Field[] { field }, true);
setFailsafeFieldValue(field, enumClass, null);
break;
}
}
}

private static void cleanEnumCache(Class<?> enumClass) throws NoSuchFieldException, IllegalAccessException {
blankField(enumClass, "enumConstantDirectory"); // Sun (Oracle?!?) JDK 1.5/6
blankField(enumClass, "enumConstants"); // IBM JDK
}

private static ConstructorAccessor getConstructorAccessor(Class<?> enumClass, Class<?>[] additionalParameterTypes)
throws NoSuchMethodException {
Class<?>[] parameterTypes = new Class[additionalParameterTypes.length + 2];
parameterTypes[0] = String.class;
parameterTypes[1] = int.class;
System.arraycopy(additionalParameterTypes, 0, parameterTypes, 2, additionalParameterTypes.length);
return reflectionFactory.newConstructorAccessor(enumClass.getDeclaredConstructor(parameterTypes));
}

private static Object makeEnum(Class<?> enumClass, String value, int ordinal, Class<?>[] additionalTypes,
Object[] additionalValues) throws Exception {
Object[] parms = new Object[additionalValues.length + 2];
parms[0] = value;
parms[1] = Integer.valueOf(ordinal);
System.arraycopy(additionalValues, 0, parms, 2, additionalValues.length);
return enumClass.cast(getConstructorAccessor(enumClass, additionalTypes).newInstance(parms));
}

/**
* Add an enum instance to the enum class given as argument

@param <T> the type of the enum (implicit)
* @param enumType the class of the enum to be modified
* @param enumName the name of the new enum instance to be added to the class.
*/
@SuppressWarnings("unchecked")
public static <T extends Enum<?>> void addEnum(Class<T> enumType, String enumName, Class<?>[] additionalTypes, Object[] additionalValues) {

   // 0. Sanity checks
   if (!Enum.class.isAssignableFrom(enumType)) {
       throw new RuntimeException("class " + enumType + " is not an instance of Enum");
   }

   // 1. Lookup "$VALUES" holder in enum class and get previous enum instances
   Field valuesField = null;
   Field[] fields = enumType.getDeclaredFields();
   for (Field field : fields) {
       if (field.getName().contains("$VALUES")) {
           valuesField = field;
           break;
       }
   }
   AccessibleObject.setAccessible(new Field[] { valuesField }, true);

   try {

       // 2. Copy it
       T[] previousValues = (T[]) valuesField.get(enumType);
       List<T> values = new ArrayList<T>(Arrays.asList(previousValues));

       // 3. build new enum
       T newValue = (T) makeEnum(enumType, enumName, values.size(), additionalTypes, additionalValues);

       // 4. add new value
       values.add(newValue);

       // 5. Set new values field
       setFailsafeFieldValue(valuesField, null, values.toArray((T[]) Array.newInstance(enumType, 0)));

       // 6. Clean enum cache
       cleanEnumCache(enumType);

   } catch (Exception e) {
       e.printStackTrace();
       throw new RuntimeException(e.getMessage(), e);
   }

}

}

KpGo的主页 KpGo | 初学一级 | 园豆:5
提问于:2019-09-10 15:53
< >
分享
最佳答案
0

解决了 理解错误 根本不用管那两个方法 根据你的枚举类型得参数个数及类型 在“蓝框”部分第一个数组是数据类型,后一个是参数,最后在测试一下ok 嘎嘎(第一行得list忽略 截完屏了懒得删)

KpGo | 初学一级 |园豆:5 | 2019-09-10 16:35
清除回答草稿
   您需要登录以后才能回答,未注册用户请先注册