JDBC 实现增删改查

public class NoteDAOImpl implements NoteDAO {
    // 增加操作
    public void insert(Note note) throws Exception {
        String sql = "INSERT INTO note(id,title,author,content) VALUES(note_sequ.nextVal,?,?,?)" ;
        PreparedStatement pstmt = null ;
        DataBaseConnection dbc = null ;
        dbc = new DataBaseConnection() ;
        try {
            pstmt = dbc.getConnection().prepareStatement(sql) ;
            pstmt.setString(1,note.getTitle()) ;
            pstmt.setString(2,note.getAuthor()) ;
            pstmt.setString(3,note.getContent()) ;
            pstmt.executeUpdate() ;
            pstmt.close() ;
        } catch (Exception e) {
            // System.out.println(e) ;
            throw new Exception("操作中出现错误！！！") ;
        } finally {
            dbc.close() ;
        }
    }
    // 修改操作
    public void update(Note note) throws Exception {
        String sql = "UPDATE note SET title=?,author=?,content=? WHERE id=?" ;
        PreparedStatement pstmt = null ;
        DataBaseConnection dbc = null ;
        dbc = new DataBaseConnection() ;
        try {
            pstmt = dbc.getConnection().prepareStatement(sql) ;
            pstmt.setString(1,note.getTitle()) ;
            pstmt.setString(2,note.getAuthor()) ;
            pstmt.setString(3,note.getContent()) ;
            pstmt.setInt(4,note.getId()) ;
            pstmt.executeUpdate() ;
            pstmt.close() ;
        } catch (Exception e) {
            throw new Exception("操作中出现错误！！！") ;
        } finally {
            dbc.close() ;
        }
    }
    // 删除操作
    public void delete(int id) throws Exception {
        String sql = "DELETE FROM note WHERE id=?" ;
        PreparedStatement pstmt = null ;
        DataBaseConnection dbc = null ;
        dbc = new DataBaseConnection() ;
        try {
            pstmt = dbc.getConnection().prepareStatement(sql) ;
            pstmt.setInt(1,id) ;
            pstmt.executeUpdate() ;
            pstmt.close() ;
        } catch (Exception e) {
            throw new Exception("操作中出现错误！！！") ;
        } finally {
            dbc.close() ;
        }
    }
    // 按ID查询，主要为更新使用
    public Note queryById(int id) throws Exception {
        Note note = null ;
        String sql = "SELECT id,title,author,content FROM note WHERE id=?" ;
        PreparedStatement pstmt = null ;
        DataBaseConnection dbc = null ;
        dbc = new DataBaseConnection() ;
        try {
            pstmt = dbc.getConnection().prepareStatement(sql) ;
            pstmt.setInt(1,id) ;
            ResultSet rs = pstmt.executeQuery() ;
            if(rs.next()) {
                note = new Note() ;
                note.setId(rs.getInt(1)) ;
                note.setTitle(rs.getString(2)) ;
                note.setAuthor(rs.getString(3)) ;
                note.setContent(rs.getString(4)) ;
            }
            rs.close() ;
            pstmt.close() ;
        } catch (Exception e) {
            throw new Exception("操作中出现错误！！！") ;
        } finally {
            dbc.close() ;
        }
        return note ;
    }
    // 查询全部
    public List queryAll() throws Exception {
        List all = new ArrayList() ;
        String sql = "SELECT id,title,author,content FROM note" ;
        PreparedStatement pstmt = null ;
        DataBaseConnection dbc = null ;
        dbc = new DataBaseConnection() ;
        try {
            pstmt = dbc.getConnection().prepareStatement(sql) ;
            ResultSet rs = pstmt.executeQuery() ;
            while(rs.next()) {
                Note note = new Note() ;
                note.setId(rs.getInt(1)) ;
                note.setTitle(rs.getString(2)) ;
                note.setAuthor(rs.getString(3)) ;
                note.setContent(rs.getString(4)) ;
                all.add(note) ;
            }
            rs.close() ;
            pstmt.close() ;
        } catch (Exception e) {
            System.out.println(e) ;
            throw new Exception("操作中出现错误！！！") ;
        } finally {
            dbc.close() ;
        }
        return all ;
    }
    // 模糊查询
    public List queryByLike(String cond) throws Exception {
        List all = new ArrayList() ;
        String sql = "SELECT id,title,author,content FROM note WHERE title LIKE ? or AUTHOR LIKE ? or CONTENT LIKE ?" ;
        PreparedStatement pstmt = null ;
        DataBaseConnection dbc = null ;
        dbc = new DataBaseConnection() ;
        try {
            pstmt = dbc.getConnection().prepareStatement(sql) ;
            pstmt.setString(1,"%"+cond+"%") ;
            pstmt.setString(2,"%"+cond+"%") ;
            pstmt.setString(3,"%"+cond+"%") ;
            ResultSet rs = pstmt.executeQuery() ;
            while(rs.next()) {
                Note note = new Note() ;
                note.setId(rs.getInt(1)) ;
                note.setTitle(rs.getString(2)) ;
                note.setAuthor(rs.getString(3)) ;
                note.setContent(rs.getString(4)) ;
                all.add(note) ;
            }
            rs.close() ;
            pstmt.close() ;
        } catch (Exception e) {
            System.out.println(e) ;
            throw new Exception("操作中出现错误！！！") ;
        } finally {
            dbc.close() ;
        }
        return all ;
    }
};