JDBC 增删改的操作（2）

JDBC 增删改的操作（2）

一、项目使用技术

​ 上一次在JDBC增删改的操作（1）中StudentBasicDAOImpl实现类代码存在较多重复，将各个方法中相同代码进行向上抽取，以此减少代码的冗余，提高代码的复用性。

二、使用实例

​ StudentBasicDAOImpl实现类的优化

public class StudentBasicDAOImpl implements StudentBasicDAO{
	//将重复代码进行向上抽取，形成update方法
	private void update(String sql, Object... arr) {
		Connection con = null;
		PreparedStatement ps = null;
		try {
			//获取数据库连接对象
			con = JDBCUtils.getConnection();
			//准备获取SQL语句的发送对象
			ps = con.prepareStatement(sql);
			// 针对可变参数做非空校验
			if (arr != null) {
				for (int i = 0; i < arr.length; i++) {
					//因为索引是从0开始,?列从1开始
					ps.setObject(i+1, arr[i]);
				}
			}
			//发送SQL语句
			ps.executeUpdate();
		} catch (SQLException e) {
			throw new RuntimeException();
		} finally {
			//关闭资源
			JDBCUtils.close(ps, con);
		}
	} 

	@Override
	public void addStudent(Student s ) {
		String sql = "insert into student values (null,?,?)";
		update(sql,s.getName(),s.getAge());
	}

	@Override
	public void deleteStudent(int sid) {
		String sql = "delete from student where id = ?";
		update(sql,sid);
	}

	@Override
	public void updateStudent(Student s) {
		String sql = "update student set name = ? ,age = ? where id = ?";
		update(sql,s.getName(),s.getAge(),s.getId());
	}

	@Override
	public List<Student> getAllStudent() {
		
		Connection con = null;
		ArrayList<Student> list = null;
		PreparedStatement ps =null;
		ResultSet rs = null;
		try {
			//获取数据库连接对象
			con = JDBCUtils.getConnection();
			// 准备SQL语句
			String sql = "select * from student";
			// 准备发送SQL语句的对象
			ps = con.prepareStatement(sql);
			// 发送SQL语句
			rs = ps.executeQuery();
			// 创建集合对象
			list = new ArrayList<Student>();
			// 针对结果集解析
			while (rs.next()) {
				int id = rs.getInt(1);
				String name = rs.getString(2);
				int age = rs.getInt(3);
				Student s = new Student(id,name,age);
				list.add(s);
			}
			return list;
		} catch (SQLException e) {
			throw new RuntimeException();
		} finally {
			JDBCUtils.close(rs, ps, con);
		}
	}

	@Override
	public Student getStudent(int sid) {

		Connection con = null;
		PreparedStatement ps =null;
		ResultSet rs = null;
		Student s =null;
		try {
			//获取数据库连接对象
			con = JDBCUtils.getConnection();
			// 准备SQL语句
			String sql = "select * from student where id = ?";
			// 准备发送SQL语句的对象
			ps = con.prepareStatement(sql);
			//确定?处的数据
			ps.setInt(1, sid);
			// 发送SQL语句
			rs = ps.executeQuery();
			// 针对结果集解析
			while (rs.next()) {
				int id = rs.getInt(1);
				String name = rs.getString(2);
				int age = rs.getInt(3);
				s = new Student(id,name,age);
				return s;
			}
		} catch (SQLException e) {
			throw new RuntimeException();
		} finally {
			JDBCUtils.close(rs, ps, con);
		}
		return s;
	}
}