GenericsUtil.java Source code

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Here is the source code for GenericsUtil.java

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/*
 * Copyright 2008-2010 the T2 Project ant the Others.
 *
 * 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 org.t2framework.commons.util;

import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class GenericsUtil {

    public static Class<?> getActualClass(Type type, Class<?> targetClass) {
        Map<TypeVariable<?>, Type> map = getTypeVariableMap(targetClass);
        return getActualClass(type, map);
    }

    public static Type getActualType(Type type, Class<?> targetClass) {
        Map<TypeVariable<?>, Type> map = getTypeVariableMap(targetClass);
        return getActualType(type, map);
    }

    private static Class<?> getActualClass(Type type, Map<TypeVariable<?>, Type> map) {
        if (Class.class.isInstance(type)) {
            return Class.class.cast(type);
        }
        if (ParameterizedType.class.isInstance(type)) {
            final Type actualType = getActualType(type, map);
            return getActualClass(actualType, map);
        } else if (TypeVariable.class.isInstance(type)) {
            final Type actualType = getActualType(type, map);
            return getActualClass(actualType, map);
        } else if (GenericArrayType.class.isInstance(type)) {
            GenericArrayType genericArrayType = GenericArrayType.class.cast(type);
            final Type genericComponentType = genericArrayType.getGenericComponentType();
            Class<?> componentClass = getActualClass(genericComponentType, map);
            return Array.newInstance(componentClass, 0).getClass();
        } else {
            return null;
        }
    }

    private static Type getActualType(Type type, Map<TypeVariable<?>, Type> map) {
        if (Class.class.isInstance(type)) {
            return type;
        } else if (ParameterizedType.class.isInstance(type)) {
            return ParameterizedType.class.cast(type).getRawType();
        } else if (TypeVariable.class.isInstance(type)) {
            return map.get(TypeVariable.class.cast(type));
        } else {
            return null;
        }
    }

    private static Map<TypeVariable<?>, Type> getTypeVariableMap(final Class<?> clazz) {
        if (clazz == null) {
            return Collections.emptyMap();
        }
        final Map<TypeVariable<?>, Type> map = new LinkedHashMap<TypeVariable<?>, Type>();
        final Class<?> superClass = clazz.getSuperclass();
        final Type superClassType = clazz.getGenericSuperclass();
        if (superClass != null) {
            gatherTypeVariables(superClass, superClassType, map);
        }
        final Class<?>[] interfaces = clazz.getInterfaces();
        final Type[] interfaceTypes = clazz.getGenericInterfaces();
        for (int i = 0; i < interfaces.length; ++i) {
            gatherTypeVariables(interfaces[i], interfaceTypes[i], map);
        }
        return map;
    }

    private static void gatherTypeVariables(final Class<?> clazz, final Type type,
            final Map<TypeVariable<?>, Type> map) {
        if (clazz == null) {
            return;
        }
        gatherTypeVariables(type, map);

        final Class<?> superClass = clazz.getSuperclass();
        final Type superClassType = clazz.getGenericSuperclass();
        if (superClass != null) {
            gatherTypeVariables(superClass, superClassType, map);
        }
        final Class<?>[] interfaces = clazz.getInterfaces();
        final Type[] interfaceTypes = clazz.getGenericInterfaces();
        for (int i = 0; i < interfaces.length; ++i) {
            gatherTypeVariables(interfaces[i], interfaceTypes[i], map);
        }
    }

    private static void gatherTypeVariables(final Type type, final Map<TypeVariable<?>, Type> map) {
        if (ParameterizedType.class.isInstance(type)) {
            final ParameterizedType parameterizedType = ParameterizedType.class.cast(type);
            final TypeVariable<?>[] typeVariables = GenericDeclaration.class.cast(parameterizedType.getRawType())
                    .getTypeParameters();
            final Type[] actualTypes = parameterizedType.getActualTypeArguments();
            for (int i = 0; i < actualTypes.length; ++i) {
                map.put(typeVariables[i], actualTypes[i]);
            }
        }
    }

}