BasicDAO

/*
    开发BasicDAO 是其他DAO 的父类
 */
public class BasicDAO <T> { //使用泛型指定具体类型

    private QueryRunner qr = new QueryRunner();
    //开发通用的dml 方法 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 (Exception e) {
            throw new RuntimeException(e); //将编译异常->运行异常, 抛出
        } finally {
            JDBCUtilsByDruid.closeConnection(null,null,connection);
        }
    }

    //返回多个对象(即查询的结果是多行的), 针对任意表
    //第二个参数 是传入一个类的Class对象 比如 Actor.class(重点), 第三个参数是传入 ? 的具体值
    //根据Actor.class 返回对应 的 ArrayList集合
    public List<T> queryMultiply(String sql, Class<T> clazz,Object... parameters) {
        Connection connection = null;

        try {
            connection = JDBCUtilsByDruid.getConnection();
            List<T> list = qr.query(connection, sql, new BeanListHandler<T>(clazz), parameters);
            return list;
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.closeConnection(null, null, connection);
        }
    }

    //查询单行单列结果的通用方法
    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 (Exception e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.closeConnection(null, null, connection);
        }
    }


    //查询单行单列的方法, 即返回单值的方法
    public Object queryScalar(String sql, Object... parameters){
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new ScalarHandler(), parameters);
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.closeConnection(null, null, connection);
        }
    }
}

public class TestDAO {
    @Test
    //测试ActorDAO 对actor表crud操作
    public void testActorDAO(){
        ActorDAO actorDAO = new ActorDAO();
        //1. 测试查询语句
        List<Actor> actors = actorDAO.queryMultiply("select * from actor where id >= ?", Actor.class, 2);
        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, 5);
        System.out.println("===查询结果===");
        System.out.println(actor);

        //3.查询单行单列
        Object o = actorDAO.queryScalar("select name from actor where id = ?", 5);
        System.out.println("===查询单行单列值===");
        System.out.println(o);

        System.out.println("===========");
        //4. dml操作 insert, update, delete
        int update = actorDAO.update("CREATE TABLE stu(id int primary key auto_increment,name varchar(20),num varchar(20))", null);
        System.out.println(update > 0 ? "执行成功" : "执行没有影响数据表");
    }
}