geronimo-jaxrs_2.0_spec/src/main/java/javax/ws/rs/core/GenericType.java

/*
 * #%L
 * Apache Geronimo JAX-RS Spec 2.0
 * %%
 * Copyright (C) 2003 - 2014 The Apache Software Foundation
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

package javax.ws.rs.core;

import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.Arrays;
import java.util.Stack;


public class GenericType<T> {


    private final Type type;

    private final Class<?> rawType;


    protected GenericType() {

        type = getTypeArgument(getClass(), GenericType.class);
        rawType = getClass(type);
    }


    public GenericType(Type genericType) {
        if (genericType == null) {
            throw new IllegalArgumentException("Type must not be null");
        }

        type = genericType;
        rawType = getClass(type);
    }


    public final Type getType() {
        return type;
    }


    public final Class<?> getRawType() {
        return rawType;
    }


    private static Class getClass(Type type) {
        if (type instanceof Class) {
            return (Class) type;
        } else if (type instanceof ParameterizedType) {
            ParameterizedType parameterizedType = (ParameterizedType) type;
            if (parameterizedType.getRawType() instanceof Class) {
                return (Class) parameterizedType.getRawType();
            }
        } else if (type instanceof GenericArrayType) {
            GenericArrayType array = (GenericArrayType) type;
            final Class<?> componentRawType = getClass(array.getGenericComponentType());
            return getArrayClass(componentRawType);
        }
        throw new IllegalArgumentException("Type parameter " + type.toString() + " not a class or " +
            "parameterized type whose raw type is a class");
    }


    private static Class getArrayClass(Class c) {
        try {
            Object o = Array.newInstance(c, 0);
            return o.getClass();
        } catch (Exception e) {
            throw new IllegalArgumentException(e);
        }
    }


    static Type getTypeArgument(Class<?> clazz, Class<?> baseClass) {

        Stack<Type> superclasses = new Stack<Type>();
        Type currentType;
        Class<?> currentClass = clazz;
        do {
            currentType = currentClass.getGenericSuperclass();
            superclasses.push(currentType);
            if (currentType instanceof Class) {
                currentClass = (Class) currentType;
            } else if (currentType instanceof ParameterizedType) {
                currentClass = (Class) ((ParameterizedType) currentType).getRawType();
            }
        } while (!currentClass.equals(baseClass));


        TypeVariable tv = baseClass.getTypeParameters()[0];
        while (!superclasses.isEmpty()) {
            currentType = superclasses.pop();

            if (currentType instanceof ParameterizedType) {
                ParameterizedType pt = (ParameterizedType) currentType;
                Class<?> rawType = (Class) pt.getRawType();
                int argIndex = Arrays.asList(rawType.getTypeParameters()).indexOf(tv);
                if (argIndex > -1) {
                    Type typeArg = pt.getActualTypeArguments()[argIndex];
                    if (typeArg instanceof TypeVariable) {


                        tv = (TypeVariable) typeArg;
                        continue;
                    } else {

                        return typeArg;
                    }
                }
            }


            break;
        }
        throw new IllegalArgumentException(currentType + " does not specify the type parameter T of GenericType<T>");
    }

    @Override
    public boolean equals(Object obj) {
        boolean result = this == obj;
        if (!result && obj instanceof GenericType) {

            GenericType<?> that = (GenericType<?>) obj;
            return this.type.equals(that.type);
        }
        return result;
    }

    @Override
    public int hashCode() {
        return type.hashCode();
    }

    @Override
    public String toString() {
        return "GenericType{" + type.toString() + "}";
    }
}