Java Utililty Methods Reflection Generic Type from Field

List of utility methods to do Reflection Generic Type from Field

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Description

The list of methods to do Reflection Generic Type from Field are organized into topic(s).

Method

ClassgetGenericMultivalueType(final Field p)
Returns the generic class of multi-value objects. 
final Type genericType = p.getGenericType();
if (genericType != null && genericType instanceof ParameterizedType) {
    final ParameterizedType pt = (ParameterizedType) genericType;
    if (pt.getActualTypeArguments() != null && pt.getActualTypeArguments().length > 0) {
        if (pt.getActualTypeArguments()[0] instanceof Class<?>) {
            return (Class<?>) pt.getActualTypeArguments()[0];
return null;
ClassgetGenericParameterClass(Field field)
get Generic Parameter Class 
Type genericType = field.getGenericType();
return (Class) ((ParameterizedType) genericType).getActualTypeArguments()[0];
ClassgetGenericParameterClass(Field field)
get Generic Parameter Class 
if (!hasGenericParameter(field)) {
    return null;
Type genericType = field.getGenericType();
return (Class) ((ParameterizedType) genericType).getActualTypeArguments()[0];
Class[]getGenericParameters(Field f)
get Generic Parameters 
Type type = f.getGenericType();
if (type instanceof ParameterizedType) {
    return Arrays.stream(((ParameterizedType) type).getActualTypeArguments())
            .map(t -> t instanceof Class ? (Class) t : null).toArray(Class[]::new);
} else {
    throw new IllegalArgumentException(f + " is not of a parameterized type");
Class[]getGenericParametersInternal(Type genericFieldType)
get Generic Parameters Internal 
if (genericFieldType instanceof ParameterizedType) {
    ParameterizedType aType = (ParameterizedType) genericFieldType;
    Type[] fieldArgTypes = aType.getActualTypeArguments();
    Class<?>[] clazzes = new Class<?>[fieldArgTypes.length];
    for (int i = 0; i < clazzes.length; i++) {
        clazzes[i] = (Class<?>) fieldArgTypes[i];
    return clazzes;
...
ClassgetGenericReturnType(Method method, Field field, boolean isAllowNull)
Returns the generic type parameter of a return value by a field or method. 
if (method == null) {
    return getGenericFieldType(field, isAllowNull);
} else {
    return getGenericReturnType(method, isAllowNull);
ClassgetGenericsTypeFromCollectionField(Field field)
Gets generics info despite runtime type erasure. 
Class<?> clazz = null;
if (List.class.isAssignableFrom(field.getType()) || Set.class.isAssignableFrom(field.getType())) {
    field.setAccessible(true);
    ParameterizedType ptype = (ParameterizedType) field.getGenericType();
    Type[] types = ptype.getActualTypeArguments();
    if (types != null && types.length > 0) {
        clazz = (Class<?>) types[0];
return clazz;
ClassgetGenericType(Field field)
Gets generic type from field (if field type is ParameterizedType ) 
Type type = field.getGenericType();
if (type instanceof ParameterizedType) {
    Type firstParameter = ((ParameterizedType) type).getActualTypeArguments()[0];
    if (!(firstParameter instanceof WildcardType)) {
        return (Class<?>) firstParameter;
return null;
...
ClassgetGenericType(Field field)
get Generic Type 
if (!Collection.class.isAssignableFrom(field.getType())) {
    return field.getType();
ParameterizedType type = (ParameterizedType) field.getGenericType();
return (Class) type.getActualTypeArguments()[0];
TypegetGenericType(Field field)
get Generic Type 
Type type = ((ParameterizedType) field.getGenericType()).getActualTypeArguments()[0];
if (type instanceof WildcardType) {
    return ((WildcardType) type).getUpperBounds()[0];
} else {
    return type;