java dao泛型设计

 

dao设计：

public interface DaoBase<T>{

            //常用的方法 CRUD

       void save(T t);

}

//----------------------------------------------------------------------

//----------------------------------------------------------------------

public class DaoSupport<T> implements DaoBase<T> {

 // 实体的类型 即T 的类型
 private Class<T> clazz;

 // 实体的名称
 private final String entityName;

 

 public DaoSupport() {
  clazz = GenericsUtil.getClazz(this.getClass());
  this.entityName = this.clazz.getName();
  System.out.println(entityName);
 }
}

//----------------------------------------------------------------------

//----------------------------------------------------------------------

 

public class GenericsUtil {
 @SuppressWarnings("unchecked")
 public static Class  getClazz(Class clazz){

//取得泛型类型
  Type type = clazz.getGenericSuperclass();
  if (!(type instanceof ParameterizedType)) {
   throw new RuntimeException();
  }

  ParameterizedType pt = (ParameterizedType) type;

//取得实际的类型
  return (Class) pt.getActualTypeArguments()[0];
 }
}

//----------------------------------------------------------------------

//----------------------------------------------------------------------

//具体的DAO，针对某个实体Bean

public interface UserDao extends DaoBase<User>{

}

public class UserDaoImpl extends DaoSupport<User> implements UserDao{

 public UserDaoImpl(){}
}

//----------------------------------------------------------------------

//----------------------------------------------------------------------

//实体

public class User{}

 

 

//----------------------------------------------------------------------

//----------------------------------------------------------------------

测试：

public class Main {

 /**
  * @param args
  */
 public static void main(String[] args) {

    UserDao dao = new UserDaoImpl();

 }

}

//----------------------------------------------------------------------

//----------------------------------------------------------------------

 

输出：User

注：这样设计可以避免类型转换，直接取到的就是User 对象了