src/main/java/com/irtimaled/bbor/common/ReflectionHelper.java

   1 package com.irtimaled.bbor.common;
   2
   3 import java.lang.reflect.Field;
   4 import java.lang.reflect.ParameterizedType;
   5 import java.lang.reflect.Type;
   6 import java.util.function.Function;
   7
   8 public class ReflectionHelper {
   9     public static <T, R> Function<T, R> getPrivateFieldGetter(Class<?> clazz, Type fieldType, Type... genericTypeArguments) {
  10         Field field = findField(clazz, fieldType, genericTypeArguments);
  11         if (field == null) return obj -> null;
  12
  13         field.setAccessible(true);
  14         return obj -> {
  15             try {
  16                 return (R) field.get(obj);
  17             } catch (IllegalAccessException ignored) {
  18                 return null;
  19             }
  20         };
  21     }
  22
  23     private static Field findField(Class<?> clazz, Type fieldType, Type[] genericTypeArguments) {
  24         for (Field field : clazz.getDeclaredFields()) {
  25             Type type = field.getGenericType();
  26             ParameterizedType genericType = TypeHelper.as(type, ParameterizedType.class);
  27             if (genericType == null) {
  28                 if (type != fieldType || genericTypeArguments.length > 0) continue;
  29                 return field;
  30             }
  31
  32             Type rawType = genericType.getRawType();
  33             if (rawType != fieldType) continue;
  34
  35             Type[] actualTypeArguments = genericType.getActualTypeArguments();
  36             if (!typesMatch(genericTypeArguments, actualTypeArguments)) continue;
  37
  38             return field;
  39         }
  40         return null;
  41     }
  42
  43     private static boolean typesMatch(Type[] left, Type[] right) {
  44         if (left.length != right.length) return false;
  45
  46         for (int index = 0; index < right.length; index++) {
  47             if (right[index] != left[index]) {
  48                 return false;
  49             }
  50         }
  51         return true;
  52     }
  53 }