private static void typeToString(StringBuilder sb, Type type, Set<Type> visited) {
if (type instanceof ParameterizedType) {
ParameterizedType parameterizedType = (ParameterizedType) type;
final Class<?> rawType = (Class<?>) parameterizedType.getRawType();
sb.append(rawType.getName());
boolean first = true;
for (Type typeArg : parameterizedType.getActualTypeArguments()) {
if (first) {
first = false;
} else {
sb.append(", ");
}
sb.append('<');
typeToString(sb, typeArg, visited);
sb.append('>');
}
} else if (type instanceof WildcardType) {
WildcardType wildcardType = (WildcardType) type;
sb.append('?');
// According to
// JLS(http://java.sun.com/docs/books/jls/third_edition/html/typesValues.html#4.5.1):
// - Lower and upper can't coexist: (for instance, this is not allowed: <? extends
// List<String> & super MyInterface>)
// - Multiple bounds are not supported (for instance, this is not allowed: <? extends
// List<String> & MyInterface>)
final Type bound;
if (wildcardType.getLowerBounds().length != 0) {
sb.append(" super ");
bound = wildcardType.getLowerBounds()[0];
} else {
sb.append(" extends ");
bound = wildcardType.getUpperBounds()[0];
}
typeToString(sb, bound, visited);
} else if (type instanceof TypeVariable<?>) {
TypeVariable<?> typeVariable = (TypeVariable<?>) type;
sb.append(typeVariable.getName());
// prevent cycles in case: <T extends List<T>>
if (!visited.contains(type)) {
visited.add(type);
sb.append(" extends ");
boolean first = true;
for (Type bound : typeVariable.getBounds()) {
if (first) {
first = false;
} else {
sb.append(" & ");
}
typeToString(sb, bound, visited);
}
visited.remove(type);
}
} else if (type instanceof GenericArrayType) {
GenericArrayType genericArrayType = (GenericArrayType) type;
typeToString(genericArrayType.getGenericComponentType());
sb.append(genericArrayType.getGenericComponentType());
sb.append("[]");
} else if (type instanceof Class) {
Class<?> typeClass = (Class<?>) type;
sb.append(typeClass.getName());
} else {
throw new IllegalArgumentException("Unsupported type: " + type);
}
}
/**
* Converts <code>Type</code> to a <code>String</code>. Supports successor interfaces:
*
* <ul>
* <li><code>java.lang.Class</code> - represents usual class
* <li><code>java.lang.reflect.ParameterizedType</code> - class with generic parameter (e.g.
* <code>List</code>)
* <li><code>java.lang.reflect.TypeVariable</code> - generic type literal (e.g. <code>List
* </code>, <code>T</code> - type variable)
* <li><code>java.lang.reflect.WildcardType</code> - wildcard type (<code>
* List<? extends Number></code>, <code>"? extends Number</code> - wildcard type)
* <li><code>java.lang.reflect.GenericArrayType</code> - type for generic array (e.g. <code>T[]
* </code>, <code>T</code> - array type)
* </ul>
*/
public static String typeToString(Type type) {
StringBuilder sb = new StringBuilder();
typeToString(sb, type, new HashSet<Type>());
return sb.toString();
}