net.sf.derquinsej.Types.java Source code

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Here is the source code for net.sf.derquinsej.Types.java

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/*
 * Copyright 2008-2009 the original author or authors.
 *
 * 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.
 */
package net.sf.derquinsej;

import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;

import com.google.common.base.Preconditions;

/**
 * Utility methods to deal with Types.
 * @author Andres Rodriguez
 */
public final class Types {
    /**
     * Not instantiable.
     */
    private Types() {
        throw new AssertionError();
    }

    /**
     * Returns the actual type arguments of the generic superclass of the
     * provided class.
     * @param subclass Class to process.
     * @return The type arguments of the generic superclass.
     * @throws IllegalArgumentException if the superclass is not a parametrized
     *             type.
     */
    public static Type[] getSuperclassTypeArguments(Class<?> subclass) {
        final Type superclass = subclass.getGenericSuperclass();
        Preconditions.checkArgument(superclass instanceof ParameterizedType, "Missing type parameter.");
        final ParameterizedType parameterized = (ParameterizedType) superclass;
        return parameterized.getActualTypeArguments();
    }

    /**
     * Returns the first actual type argument of the generic superclass of the
     * provided class.
     * @param subclass Class to process.
     * @return The first type argument of the generic superclass.
     * @throws IllegalArgumentException if the superclass is not a parametrized
     *             type.
     */
    public static Type getSuperclassTypeArgument(Class<?> subclass) {
        return getSuperclassTypeArguments(subclass)[0];
    }

    /**
     * Returns the raw type corresponding to the provided type.
     * @param type Type.
     * @return The raw type.
     */
    public static Class<?> getRawType(Type type) {
        if (type instanceof Class<?>) {
            return (Class<?>) type;
        } else if (type instanceof ParameterizedType) {
            final Type rawType = ((ParameterizedType) type).getRawType();
            Preconditions.checkArgument(rawType instanceof Class<?>, "Unknown case");
            return (Class<?>) rawType;
        } else if (type instanceof GenericArrayType) {
            return Object[].class;
        } else if (type instanceof TypeVariable<?>) {
            return Object.class;
        }
        throw new IllegalArgumentException("Unsupported case");
    }
}