学生成绩管理系统添加班级模块错误，下面是数据库的操作代码和控制台的代码，还有错误提示，求帮忙

//添加班级
public void addClass(int pid,String className) {
String sql="insert into class (pid,classname) values(?,?)";
Connection connection=null;
PreparedStatement p=null;
try {
connection=DbUtil.getConnection();
//手动提交事务
connection.setAutoCommit(false);
p=(PreparedStatement) connection.prepareStatement(sql);
p.setInt(1, pid);
p.setString(2, className);
p.executeUpdate();
//获取当前班级的父班级
Classes parentClass=findClassById(pid);
//如果父班级为叶子
if (parentClass.getLeaf()==1) {
modLeaf(connection, parentClass.getClassId(), 0);
}
//提交事务
connection.commit();
} catch (Exception e) {
e.printStackTrace();
if (connection!=null) {
try {
connection.rollback();
} catch (Exception e1) {

            e1.printStackTrace();
        }
    }
} finally {
    DbUtil.colse(p);
    //恢复成自动提交
    DbUtil.setAutoCommit(connection, true);
    DbUtil.colse(connection);
}

}
/**

• 修改叶子值如果为叶子
• @throws SQLException */

private void modLeaf(Connection connection,int classId,int leaf) throws SQLException{
String sql="update class set leaf=? where classid=?";
PreparedStatement p=null;

try {
p=(PreparedStatement) connection.prepareStatement(sql);
p.setInt(1, leaf);
p.setInt(2, classId);
p.executeUpdate();
} finally {
DbUtil.colse(p);
}
}

/**

• 根据ID查找班级
• 查询父班级是否为叶子
• 如果存在返回班级，不存在返回空

• @return
  */
  public Classes findClassById(int classId) {
  String sql="select *form class where classid=?" ;
  Connection connection=null;
  PreparedStatement p=null;
  ResultSet rs=null;
  Classes classes=null;
  try {
  connection=DbUtil.getConnection();
  p=(PreparedStatement) connection.prepareStatement(sql);
  rs=(ResultSet) p.executeQuery();
  if(rs.next()) {
  classes=new Classes();
  classes.setClassId(classId);
  classes.setClassName(rs.getString("classname"));
  classes.setPid(rs.getInt("pid"));
  classes.setLeaf(rs.getInt("leaf"));
  }
  } catch (Exception e) {
  e.printStackTrace();
  } finally {
  DbUtil.colse(rs);
  DbUtil.colse(p);
  DbUtil.colse(connection);
  }
  return classes;
  }
  }
  控制台代码，应该没错，s为输出的添加信息
  int pid=Integer.parseInt(s.substring(s.indexOf("=")+1, s.indexOf(",")));
  String className=s.substring(s.lastIndexOf("=")+1, s.length());
  ClassManage.getInstance().addClass(pid, className);

  错误信息：
  1-添加班级
  2-删除班级
  3-修改班级
  4-查询班级
  q-退出
  1
  请输入添加的班级名（classname=#）:
  pid=3,classname=一年一班_01
  java.sql.SQLException: Field 'leaf' doesn't have a default value
  at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:946)
  at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2985)
  at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1631)
  at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1723)
  at com.mysql.jdbc.Connection.execSQL(Connection.java:3256)
  at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1313)
  at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1585)
  at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1500)
  at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1485)
  at com.coursemanage.lsq.ClassManage.addClass(ClassManage.java:67)
  at com.coursecontroller.lsq.ClassController.main(ClassController.java:47)