标签：练习题 ps PreparedStatement String System sql println P28 out

练习1 插入数据

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.println("输入用户名：");
    String name = scanner.next();
    System.out.println("输入邮箱：");
    String email = scanner.next();
    System.out.println("输入生日：");
    String birthday = scanner.next();

    String sql="insert into customers(name,email,birth)values(?,?,?)";
    int insertCount = update(sql, name, email, birthday);
    if (insertCount>0){
        System.out.println("添加成功");
    }else {
        System.out.println("添加失败");
    }
}

//通用的增删改操作的方法
public static int update(String sql, Object... args)  {//占位符的个数与可变形参的长度一致
    Connection conn = null;
    PreparedStatement ps = null;
    try {
        //1.获取数据库的连接
        conn = JDBCUtil.getConnection();
        //2.预编译sql语句，返回preparedstatement实例
        ps = conn.prepareStatement(sql);
        //3.填充占位符
        for (int i=0;i<args.length;i++){
            ps.setObject(i+1, args[i]);//注意索引
        }
        //4.执行
       return ps.executeUpdate();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        //5.关闭资源
        JDBCUtil.closeResource(conn, ps);
    }
    return 0;
}

练习2 查询考生四六级成绩

//课后练习2
public class Exer2Test {
    /*
    问题1：向examstudent表中添加一条数据
    Type:
    IDCard:
    ExamCard:
    StudentName:
    Location:
    Grade:
     */
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("四级/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 studentName = scanner.next();
        System.out.println("所在城市:");
        String location = scanner.next();
        System.out.println("成绩:");
        int grade = scanner.nextInt();

        String sql="insert into examStudent(type,IDCard,examCard,studentName,location,grade) values(?,?,?,?,?,?)";
        int insertCount = update(sql, type, IDCard, examCard, studentName, location, grade);
        if (insertCount>0){
            System.out.println("添加成功");
        }else {
            System.out.println("添加失败");
        }
    }


    //通用的增删改操作的方法
    public static int update(String sql, Object... args)  {//占位符的个数与可变形参的长度一致
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            //1.获取数据库的连接
            conn = JDBCUtil.getConnection();
            //2.预编译sql语句，返回preparedstatement实例
            ps = conn.prepareStatement(sql);
            //3.填充占位符
            for (int i=0;i<args.length;i++){
                ps.setObject(i+1, args[i]);//注意索引
            }
            //4.执行
            return ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //5.关闭资源
            JDBCUtil.closeResource(conn, ps);
        }
        return 0;
    }
}

public class Exer3Test {
    public static void main(String[] args) {
        System.out.println("请输入类型:");
        System.out.println("a.准考证号");
        System.out.println("b.身份证号");
        Scanner scanner = new Scanner(System.in);
        String selection = scanner.next();
        if ("a".equalsIgnoreCase(selection)){
            System.out.println("请输入准考证号:");
            String examCard = scanner.next();
            String sql="select FlowID flowID,Type type,IDCard,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where examCard=?";

            Student student = getInstance(Student.class, sql,examCard);
            if (student!=null){
                System.out.println(student);
            }else {
                System.out.println("输入的准考证号有误");
            }

        }else if ("b".equalsIgnoreCase(selection)){
            System.out.println("请输入身份证号:");
            String IDCard = scanner.next();
            String sql1="select FlowID flowID,Type type,IDCard,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where IDCard=?";

            Student student = getInstance(Student.class, sql1,IDCard);
            if (student!=null){
                System.out.println(student);
            }else {
                System.out.println("输入的身份证号有误");
            }
        }else{
            System.out.println("输入有误，请重新进入程序");
        }
    }
    //问题2：根据身份证号或准考证号查询学生成绩信息


    public static  <T> T getInstance(Class<T> clazz,String sql,Object ...args){
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = JDBCUtil.getConnection();
            ps = conn.prepareStatement(sql);

            for (int i=0;i< args.length;i++){
                ps.setObject(i+1, args[i]);
            }
            //执行，获取结果集
            rs = ps.executeQuery();
            //获取结果集的元数据
            ResultSetMetaData rsmd = rs.getMetaData();
            //获取列数
            int columnCount = rsmd.getColumnCount();
            if (rs.next()){
                T t = clazz.newInstance();
                for (int i=0;i<columnCount;i++){
                    //获取每个列的值:通过ResultSet
                    Object columnValue = rs.getObject(i + 1);
                    //获取每个列的列名：通过ResultSetMetaData

                    //获取的是列名
                    //String columnName = rsmd.getColumnName(i + 1);

                    //获取列的别名
                    String columnLabel = rsmd.getColumnLabel(i + 1);

                    //通过反射将对象指定名columnName的属性赋值给指定的值columnValue
                    Field field =clazz.getDeclaredField(columnLabel);
                    field.setAccessible(true);
                    field.set(t, columnValue);
                }
                return t;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtil.closeResource(conn, ps,rs);
        }

        return null;
    }
}

练习3 删除指定的学生信息

//问题3：删除指定的学生信息
public class Exer4Test {
    public static void main(String[] args) {
        System.out.println("请输入学生的考号:");
        Scanner scanner = new Scanner(System.in);
        String examCard = scanner.next();
        //查询指定准考证号的学生
        String sql="select FlowID flowID,Type type,IDCard,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where examCard=?";
        Student student = getInstance(Student.class, sql, examCard);
        if (student==null){
            System.out.println("查无此人，请重新输入");
        }else {
            String sql1="delete from examstudent where examCard=?";
            int deleteCount = update(sql1, examCard);
            if (deleteCount>0){
                System.out.println("删除成功");
            }
        }
    }
    public static  <T> T getInstance(Class<T> clazz,String sql,Object ...args){
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = JDBCUtil.getConnection();
            ps = conn.prepareStatement(sql);

            for (int i=0;i< args.length;i++){
                ps.setObject(i+1, args[i]);
            }
            //执行，获取结果集
            rs = ps.executeQuery();
            //获取结果集的元数据
            ResultSetMetaData rsmd = rs.getMetaData();
            //获取列数
            int columnCount = rsmd.getColumnCount();
            if (rs.next()){
                T t = clazz.newInstance();
                for (int i=0;i<columnCount;i++){
                    //获取每个列的值:通过ResultSet
                    Object columnValue = rs.getObject(i + 1);
                    //获取每个列的列名：通过ResultSetMetaData

                    //获取的是列名
                    //String columnName = rsmd.getColumnName(i + 1);

                    //获取列的别名
                    String columnLabel = rsmd.getColumnLabel(i + 1);

                    //通过反射将对象指定名columnName的属性赋值给指定的值columnValue
                    Field field =clazz.getDeclaredField(columnLabel);
                    field.setAccessible(true);
                    field.set(t, columnValue);
                }
                return t;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtil.closeResource(conn, ps,rs);
        }

        return null;
    }
    //通用的增删改操作的方法
    public static int update(String sql, Object... args)  {//占位符的个数与可变形参的长度一致
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            //1.获取数据库的连接
            conn = JDBCUtil.getConnection();
            //2.预编译sql语句，返回preparedstatement实例
            ps = conn.prepareStatement(sql);
            //3.填充占位符
            for (int i=0;i<args.length;i++){
                ps.setObject(i+1, args[i]);//注意索引
            }
            //4.执行
            return ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //5.关闭资源
            JDBCUtil.closeResource(conn, ps);
        }
        return 0;
    }
}

标签：练习题,ps,PreparedStatement,String,System,sql,println,P28,out
来源： https://blog.csdn.net/weixin_54671087/article/details/121961287

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