这种泛型反射需求如何实现?

Question

interface IBaseDao <T extends Serializable, ID extends Serializable>{}

@Component("baseDao")
public class BaseDao<T extends Serializable, ID extends Serializable> extends HibernateDaoSupport implements IBaseDao<T,ID>{

private Class<T> entityClazz;

当new BaseDao<User,Integer>的时候
如何通过反射在BaseDao的构造中获得User的类
然后可以setter进entityClazz中
现在碰到的问题就是这个反射不会写!
倘若我不实现IBaseDao接口,又是否能实现?
百度了,但是根据样本,发现不能出效果,不知为何?

高手们是否能提供一个解决方案?谢谢了

Answer 1

这样啊!感谢回复指教!

Answer 2

可以实现的,给你一个代码片段

/*

 * Copyright @ 2006-2010 by The Jxva Framework 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.

 */

package com.jxva.dao;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

/**

 *

 * @author  The Jxva Framework Foundation

 * @since   1.0

 * @version 2009-03-30 15:25:07 by Jxva

 */

public abstract class GenericDao<T> extends BaseDao{

private static final Map<Class<?>,Class<?>> cache=new HashMap<Class<?>,Class<?>>();

protected final Class<T> entityClass;  

@SuppressWarnings("unchecked")

public GenericDao(){

super();

Class<?> cls=getClass();

Class<?> result=cache.get(cls);

if(result!=null){

entityClass=(Class<T>)result;

}else{

entityClass=(Class<T>)getEntityClass(cls);

cache.put(cls,entityClass);

}

}

private Class<?> getEntityClass(Class<?> cls){

Type type=cls.getGenericSuperclass();

if(type.toString().lastIndexOf('>')>-1){

return (Class<?>)((ParameterizedType)type).getActualTypeArguments()[0];

}else{

throw new DAOException("com.jxva.dao.GenericDao's subclass must be generic class");

}

}

public Class<T> getEntityClass(){

return this.entityClass;

}

public T get(Object pkey) {

return dao.get(entityClass,pkey);

}

public int delete(Object pkey){

return dao.delete(entityClass,pkey);

}

public List<T> findAll(){

return dao.find(entityClass);

}

public List<T> findPageBean(PageBean pageBean){

return dao.findPageBean(entityClass, pageBean);

}

public  List<T> findPaginated(int index,int size){

return dao.findPaginated(entityClass, index, size);

}

}

Answer 3

泛型的信息在编译时就被编译器给擦除了，无法获取实例化BaseDao时T的具体类型