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The Fastnate Data Importer for offline SQL generation
package org.fastnate.data.util;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.NoSuchElementException;
/**
* Helper for inspection of classes.
*
* @author Tobias Liefke
*/
public final class ClassUtil {
private static Type getActualTypeArgument(final Class instanceClass, final Class superClass,
final int argumentIndex) {
final List parents = new ArrayList<>();
parents.add(instanceClass.getGenericSuperclass());
parents.addAll(Arrays.asList(instanceClass.getGenericInterfaces()));
for (final Type parentType : parents) {
final Class parentClass = parentType instanceof ParameterizedType ? (Class) ((ParameterizedType) parentType)
.getRawType() : (Class) parentType;
// First check if we found the super class or interface
if (superClass.equals(parentClass)) {
// We found the requested super class - use the binding
return ((ParameterizedType) parentType).getActualTypeArguments()[argumentIndex];
} else if (parentClass != null && superClass.isAssignableFrom(parentClass)) {
// Else step up
final Type type = getActualTypeArgument(parentClass.asSubclass(superClass), superClass, argumentIndex);
if (type instanceof Class) {
return type;
} else if (type instanceof TypeVariable) {
return ((ParameterizedType) parentType).getActualTypeArguments()[Arrays.asList(
parentClass.getTypeParameters()).indexOf(type)];
}
}
}
return null;
}
/**
* Resolves the actual binding of a generic type that was specified in a superclass and bound in a subclass.
*
* @param instanceClass
* the implementing class
* @param superClass
* the superclass or interface which specifies the generic type variable
* @param argumentIndex
* the index of the type variable in the superclass definition (0 = the first type variable)
* @return the bound class for the variable in instanceClass
*/
public static Class getActualTypeBinding(final Class instanceClass,
final Class superClass, final int argumentIndex) {
Type type = getActualTypeArgument(instanceClass, superClass, argumentIndex);
if (type instanceof TypeVariable) {
type = ((TypeVariable) type).getBounds()[0];
}
if (type instanceof ParameterizedType) {
type = ((ParameterizedType) type).getRawType();
}
if (type instanceof Class) {
return (Class) type;
}
throw new NoSuchElementException("Can't find binding for the " + argumentIndex + ". argument of " + superClass
+ " in " + instanceClass);
}
private ClassUtil() {
// Helper class
}
}