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138.BasicDao

基本说明：

1. DAO：data access object 数据访问对象

2. 这样的通用类，称为 BasicDao，是专门和数据库交互的，即完成对数据库(表)的crud操作

3. 在BasicDao 基础上，实现一张表对应一个Dao，更好的完成功能，比如 Customer表

代码实现：

public class BasicDao<T> { //泛型指定具体的类型private QueryRunner qr = new QueryRunner();//开发通用的dml发明合法，针对任意的表public int update(String sql, Object... parameters) {Connection connection = null;try{connection = JDBCUtilsByDruid.getConnection();int update = qr.update(connection, sql, parameters);return update;} catch (SQLException e) {throw new RuntimeException(e);//将编译异常转成运行异常}finally {JDBCUtilsByDruid.close(null,null,connection);}}//返回多个对象（即查询的结果是多行的），针对任意表public List<T> queryMulti(String sql, Class<T> clazz,Object... parameters) {Connection connection = null;try{connection = JDBCUtilsByDruid.getConnection();return qr.query(connection, sql, new BeanListHandler<T>(clazz), parameters);
​} catch (SQLException e) {throw new RuntimeException(e);//将编译异常转成运行异常}finally {JDBCUtilsByDruid.close(null,null,connection);}}
​//查询单行结果的通用方法public T querySingle(String sql, Class<T> clazz, Object... parameters) {Connection connection = null;try{connection = JDBCUtilsByDruid.getConnection();return qr.query(connection, sql, new BeanHandler<T>(clazz), parameters);} catch (SQLException e) {throw new RuntimeException(e);//将编译异常转成运行异常}finally {JDBCUtilsByDruid.close(null,null,connection);}}
​//查询单行单列的方法，返回单值的方法public Object queryScalar(String sql, Object... parameters) {Connection connection = null;try{connection = JDBCUtilsByDruid.getConnection();return qr.query(connection, sql, new ScalarHandler<>(), parameters);} catch (SQLException e) {throw new RuntimeException(e);//将编译异常转成运行异常}finally {JDBCUtilsByDruid.close(null,null,connection);}}
}

测试ActorDAO 对 actor表的crud操作

public void testActorDAO() {ActorDAO actorDAO = new ActorDAO();//1.查询List<Actor> actors = actorDAO.queryMulti("select * from actor where id >= ?",Actor.class, 1);System.out.println("===查询结果===");for(Actor actor : actors) {System.out.println(actor);}//2.查询单行记录Actor actor = actorDAO.querySingle("select * from actor where id = ?",Actor.class, 1);System.out.println("===查询单行结果===");System.out.println(actor);}
​//3.查询单行单列Object o = actorDAO.queryScalar("select name from actor where id = ?",6);System.out.println("===查询单行单列值===");System.out.println(o)//4. dml操作 insert，update，deleteint update = actorDAO.update("insert into actor values(null,?,?,?,?)","张无忌","男","2000-1-1","111");System.out.println(update > 0 ? "执行成功" : "执行没有影响表");
}