Java数据库操作的一些注意

//课后练习

public class task3 {

	//添加一条数据

	@Test

	public void testInsert()

	{

		int id=1;

		Scanner scanner =new Scanner(System.in);

		System.out.println("四季/六级");

		int type=scanner.nextInt();

		System.out.println("身份证号");

		String idCard = scanner.next();

		System.out.println("准考证号");

		String examCard=scanner.next();

		System.out.println("学生姓名：");

		String name=scanner.next();

		System.out.println("学生成绩：");

		int grade=scanner.nextInt();

		String sql="insert into examstudent(flowId,type,idCard,examCard,name,Grade)values(?,?,?,?,?,?)"; //

	　　　　　　int insertCount=update(sql,id++,type,idCard,examCard,name,grade); //根据返回值判断是否插入成功

		if(insertCount>0)

		{

			System.out.println("插入成功");

		}

		else{

			System.out.println("插入失败");

		}

	}

	//插入数据函数

	public int  update(String sql,Object ...args)

	{

		Connection conn=null;

		PreparedStatement ps=null;

		try {

			 conn=JDBCUtils.getConnction5();

			 ps=(PreparedStatement) conn.prepareStatement(sql);

			for(int i=0;i<args.length;i++){

				ps.setObject(i+1, args[i]);

			}

			return  ps.executeUpdate();  //返回影响了多少条数据

		} catch (SQLException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		} catch (Exception e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}finally{

			JDBCUtils.closeResource(conn, ps);

		}

		return 0;

	}

}

@Test

	public void queryWithId()

	{

		System.out.println("请选择您要输入的类型：");

		System.out.println("a.准考证号");

		System.out.println("b.身份证号");

		Scanner scanner=new Scanner(System.in);

		String slection =scanner.next();

		if("a".equalsIgnoreCase(slection))

		{

			System.out.println("请输入注考证号：");

			String examCard=scanner.next();

			String sql="select flowId flowId,idCard IDCard,examCard examCard,name name,Grade grade from examstudent where examCard=?"; //为每个字段取别名，别名需要和Student对象中的数据类型一致

			Student student=getInstance(Student.class, sql, examCard);

					System.out.println(student);

		}else if("b".equalsIgnoreCase(slection))

		{

			System.out.println("请输入身份证号：");

			String Idcard=scanner.next();

			String sql="select flowId flowId,idCard IDCard,examCard examCard,name name,Grade grade from examstudent where examCard=?";

			Student student=getInstance(Student.class, sql, Idcard);   //调用通用查询接口

					System.out.println(student);

		}

		else

		{

			System.out.println("您输入的数据有误，请重新输入！");

		}

	}

	//通用查询的函数

public <T> T getInstance(Class<T> clazz,String sql,Object ...args){

		Connection conn =null;

		PreparedStatement ps=null;

		ResultSet rs=null;

		try {

			conn=JDBCUtils.getConnction5();

			ps=(PreparedStatement) conn.prepareStatement(sql);

			for(int i=0;i<args.length;i++)

			{

				ps.setObject(i+1,args[i]);

			}

			rs=ps.executeQuery();

			ResultSetMetaData rsmd=(ResultSetMetaData) rs.getMetaData();

			int columnCount=rsmd.getColumnCount();

			if(rs.next()){

				T t=clazz.newInstance();  //反射

				for(int i=0;i<columnCount;i++){

					Object columValue=rs.getObject(i+1);

					String columnLable1=rsmd.getColumnLabel(i+1);

					java.lang.reflect.Field field=clazz.getDeclaredField(columnLable1);

					field.setAccessible(true);

					field.set(t,columValue);

				}

				return t;

			}

		} catch (SQLException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		} catch (Exception e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

		return null;

	}

}