Java Reflection Generic Type from Field getGenericType(Type type, Type fieldType)

Description

get Generic Type

License

Open Source License

Declaration

public static Type getGenericType(Type type, Type fieldType) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.GenericArrayType;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.Arrays;

public class Main {
    public static Type getGenericType(Type type, Type fieldType) {
        if (type instanceof ParameterizedType) {
            Class<?> klass = getTypeClass(type);
            if (fieldType instanceof TypeVariable) {
                TypeVariable<?>[] typeVariables = klass.getTypeParameters();
                for (int i = 0; i < typeVariables.length; i++) {
                    TypeVariable<?> typeVariable = typeVariables[i];
                    if (typeVariable.equals(fieldType)) {
                        fieldType = ((ParameterizedType) type).getActualTypeArguments()[i];
                        break;
                    }/*from ww w . ja  v a 2s .  co m*/
                }
            } else if (fieldType instanceof ParameterizedType) {
                Type[] typeArguements = ((ParameterizedType) fieldType).getActualTypeArguments();
                int hashCode = Arrays.hashCode(typeArguements);
                for (int i = 0; i < typeArguements.length; i++) {
                    typeArguements[i] = getGenericType(type, typeArguements[i]);
                }
                if (hashCode != Arrays.hashCode(typeArguements)) {
                    try {
                        Field field = fieldType.getClass().getDeclaredField("actualTypeArguments");
                        field.setAccessible(true);
                        field.set(fieldType, typeArguements);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return fieldType;
    }

    @SuppressWarnings("unchecked")
    public static <T> Class<T> getTypeClass(Type type) {
        Class<T> klass = null;
        if (type instanceof Class<?>) {
            klass = (Class<T>) type;
        } else if (type instanceof ParameterizedType) {
            klass = (Class<T>) ((ParameterizedType) type).getRawType();
        } else if (type instanceof GenericArrayType) {
            klass = (Class<T>) Array
                    .newInstance(getTypeClass(((GenericArrayType) type).getGenericComponentType()), 0).getClass();
        }
        return klass;
    }

    public static <T> T newInstance(Class<T> klass) {
        T t = null;
        try {
            Constructor<T> constructor = klass.getDeclaredConstructor();
            if (constructor != null) {
                constructor.setAccessible(true);
                t = constructor.newInstance();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return t;
    }
}

Related

1. getGenericType(Field field)
2. getGenericType(Field field)
3. getGenericType(Field field)
4. getGenericType(Field field)
5. getGenericType(Field field)
6. getGenericTypeArguments(final Field field)
7. getGenericTypeOfCollectionField(Field field)
8. getGenericTypes(Field field)
9. getGenericTypes(Field field)