Java BasicDAO的详解

//开发BasicDAO,是其他DAO的父类
public class BasicDAO<T> {//泛型指定具体的类型
    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 (SQLException e) {
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }
    //返回多个对象(即查询的结果是多行)，针对任意表
    /**
     * @param sql        sql语句可以有?号
     * @param clazz      传入一个类的Class对象 比如Actor.class
     * @param parameters 传入? 的具体的值，可以是多个
     * @return 根据Actor.class 返回对应的ArrayList集合
     */
    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) {
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
        } 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) {
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(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 (SQLException e) {
            //将编译异常转换为运行异常，抛出
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }
}

public class ActorDAO extends BasicDAO<Actor>{
    //1.就有BasicDao的方法
    //2.根据业务需求，可以编写特有的方法
}

//Actor对象 和 actor表的记录对应
public class Actor {//JavaBean ,POJO,Domain对象
    private Integer id;
    private String name;
    private String sex;
    private Date borndate;
    private String phone;
    public Actor() {//一定要给一个无参构造器[反射需要]
    }
    public Actor(Integer id, String name, String sex, Date borndate, String phone) {
        this.id = id;
        this.name = name;
        this.sex = sex;
        this.borndate = borndate;
        this.phone = phone;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Date getBorndate() {
        return borndate;
    }
    public void setBorndate(Date borndate) {
        this.borndate = borndate;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    @Override
    public String toString() {
        return "Actor{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", borndate=" + borndate +
                ", phone='" + phone + '\'' +
                '}';
    }
}

public class TestDAO {
    //测试ActorDAO 对Actor表的crud操作
    @Test
    public void testActorDAO() {
        ActorDAO actorDAO = new ActorDAO();
        //1.查询多行记录
        List<Actor> actors = actorDAO.queryMulti("SELECT * FROM actor WHERE id >= ?", Actor.class, 2);
        System.out.println("===查询结果===");
        for (Actor actor : actors) {
            System.out.println(actor);
        }
        //查询单行记录
        Actor actor = actorDAO.querySingle("SELECT * FROM actor WHERE id = ?", Actor.class, 2);
        System.out.println("===查询单行结果===");
        System.out.println(actor);
        //查询单行单例
        Object o = actorDAO.queryScalar("SELECT name FROM actor WHERE id = ?", 2);
        System.out.println("===查询单行单列===");
        System.out.println(o);
        //DML操作 (insert,delete,update)
//        int affectedRows = actorDAO.update("UPDATE actor SET NAME=? WHERE id = ?", "林青霞", 2);
//        int affectedRows = actorDAO.update("INSERT INTO actor VALUES(NULL,?,?,?,?)", "许三多", "男","1999-01-01","123456");
        int affectedRows = actorDAO.update("DELETE FROM actor WHERE id = ?", "5");
        System.out.println(affectedRows > 0 ? "执行成功" : "执行没有影响表");
    }
}

===查询结果===
Actor{id=2, name='林青霞', sex='男', borndate=1980-01-03 08:00:00.0, phone='123456789'}
Actor{id=3, name='张三丰', sex='男', borndate=1999-01-10 08:00:00.0, phone='1234567890'}
Actor{id=5, name='许三多', sex='男', borndate=1999-01-01 08:00:00.0, phone='123456'}
===查询单行结果===
Actor{id=2, name='林青霞', sex='男', borndate=1980-01-03 08:00:00.0, phone='123456789'}
===查询单行单列===
林青霞
执行成功