io.honeybadger.com.fasterxml.jackson.core.type.TypeReference Maven / Gradle / Ivy
package com.fasterxml.jackson.core.type;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
/**
* This generic abstract class is used for obtaining full generics type information
* by sub-classing; it must be converted to {@link ResolvedType} implementation
* (implemented by JavaType
from "databind" bundle) to be used.
* Class is based on ideas from
* http://gafter.blogspot.com/2006/12/super-type-tokens.html,
* Additional idea (from a suggestion made in comments of the article)
* is to require bogus implementation of Comparable
* (any such generic interface would do, as long as it forces a method
* with generic type to be implemented).
* to ensure that a Type argument is indeed given.
*
* Usage is by sub-classing: here is one way to instantiate reference
* to generic type List<Integer>
:
*
* TypeReference ref = new TypeReference<List<Integer>>() { };
*
* which can be passed to methods that accept TypeReference, or resolved
* using TypeFactory
to obtain {@link ResolvedType}.
*/
public abstract class TypeReference implements Comparable>
{
protected final Type _type;
protected TypeReference()
{
Type superClass = getClass().getGenericSuperclass();
if (superClass instanceof Class) { // sanity check, should never happen
throw new IllegalArgumentException("Internal error: TypeReference constructed without actual type information");
}
/* 22-Dec-2008, tatu: Not sure if this case is safe -- I suspect
* it is possible to make it fail?
* But let's deal with specific
* case when we know an actual use case, and thereby suitable
* workarounds for valid case(s) and/or error to throw
* on invalid one(s).
*/
_type = ((ParameterizedType) superClass).getActualTypeArguments()[0];
}
public Type getType() { return _type; }
/**
* The only reason we define this method (and require implementation
* of Comparable
) is to prevent constructing a
* reference without type information.
*/
@Override
public int compareTo(TypeReference o) { return 0; }
// just need an implementation, not a good one... hence ^^^
}