Get Actual Class : Type « Reflection « Java

1. Java
2. Reflection
3. Type

Get Actual Class

        
/*
 * 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]);
      }
    }
  }

}

   
    
    
    
    
    
    
    
  

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