在数据库中插入数据

Question

我有以下文件：

1. Student.sql
2. 的index.jsp
3. sampleReport.jsp
   
4. StudentServlet（com.ydp.controller）
   
5. StudentDao（com.ydp.dao）
   
6. StudentDaoImpl（com.ydp.dao.impl）
   
7. 学生（com.ydp.domains）。
   我的数据库连接是 jdbc：derby：// localhost：1527 / sample [APP上的app]。

StudentDaoImpl.java ：

public class StudentDaoImpl implements StudentDao {
private DataSource ds;
private Connection con;
private PreparedStatement preparedStatement;
private ResultSet rs;
public StudentDaoImpl() {
}
@Override
public void create(Student student) throws SQLException, NamingException {
    long id = getID();
    ds = getStudentDS();
    con = ds.getConnection();
    preparedStatement = con.prepareStatement("INSERT INTO STUDENT(ID,STUDENTNAME,EMAIL,AGE,COUNTRY) VALUES(?,?,?,?,?)");
    preparedStatement.setLong(1, id);
    preparedStatement.setString(2, student.getStudentName());
    preparedStatement.setString(3, student.getEmail());
    preparedStatement.setInt(4, student.getAge());
    preparedStatement.setString(5, student.getCountry());
    preparedStatement.executeUpdate();
    con.close();
}
@Override
public List<Student> findAll() throws NamingException, SQLException {

    List<Student> list = new ArrayList<>();
    ds = getStudentDS();
    con = ds.getConnection();
    preparedStatement = con.prepareStatement("SELECT * FROM STUDENT");
    rs = preparedStatement.executeQuery();
    while (rs.next()) {
        Student student = new Student();
        student.setId(rs.getLong("ID"));
        student.setStudentName(rs.getString("STUDENTNAME"));
        student.setEmail(rs.getString("EMAIL"));
        student.setAge(rs.getInt("AGE"));
        student.setCountry(rs.getString("COUNTRY"));
        list.add(student);
    }
    con.close();
    return list;
}
@Override
public Student find(long id) throws NamingException, SQLException {

    Student student = null;
    ds = getStudentDS();
    con = ds.getConnection();
    preparedStatement = con.prepareStatement("SELECT * FROM STUDENT WHERE ID=?");
    preparedStatement.setLong(1, id);
    rs = preparedStatement.executeQuery();
    if (rs.next()) {
        student = new Student();
        student.setId(rs.getLong("ID"));
        student.setStudentName(rs.getString("STUDENTNAME"));
        student.setEmail(rs.getString("EMAIL"));
        student.setAge(rs.getInt("AGE"));
        student.setCountry(rs.getString("COUNTRY"));
    }
    con.close();
    return student;
}
@Override
public void edit(Student student) throws NamingException, SQLException {
    ds = getStudentDS();
    con = ds.getConnection();
    preparedStatement = con.prepareStatement("UPDATE STUDENT SET STUDENTNAME=?, EMAIL=?, AGE=?, COUNTRY=? WHERE ID=?");
    preparedStatement.setString(1, student.getStudentName());
    preparedStatement.setString(2, student.getEmail());
    preparedStatement.setInt(3, student.getAge());
    preparedStatement.setString(4, student.getCountry());
    preparedStatement.setLong(5, student.getId());
    preparedStatement.executeUpdate();
    con.close();
}
@Override
public void delete(long id) throws NamingException, SQLException {
    ds = getStudentDS();
    con = ds.getConnection();
    preparedStatement = con.prepareStatement("DELETE FROM STUDENT WHERE ID=?");
    preparedStatement.setLong(1, id);
    preparedStatement.executeUpdate();
    con.close();
}
private DataSource getStudentDS() throws NamingException {
    Context c = new InitialContext();
    return (DataSource) c.lookup("java:comp/env/StudentDS");
}
private long getID() throws NamingException, SQLException {
    long id = 0;
    ds = getStudentDS();
    con = ds.getConnection();
    preparedStatement = con.prepareStatement("SELECT MAX (ID) FROM STUDENT");
    rs = preparedStatement.executeQuery();
    if (rs.next()) {
        id = rs.getLong(1);
    }
    id++;
    con.close();
    return id;
} }

StudentDao.java ：

public interface StudentDao {
 public void create(Student student) throws SQLException, NamingException;
 public List<Student> findAll() throws SQLException, NamingException;
 public Student find(long id) throws SQLException, NamingException;
 public void edit(Student student) throws SQLException, NamingException;
 public void delete(long id) throws SQLException, NamingException;
}

错误：我无法将数据保存到数据库中   我的朋友告诉（尝试使用try catch at public void create（学生）和getID。不要使用抛出异常）我使用try catch但它不起作用。