Jsp中无法显示数据答案

【问题标题】：Cannot display data in JspJsp中无法显示数据
【发布时间】：2021-03-13 20:15:48
【问题描述】：

我有一个小问题，我只是想在我的表格中显示数据，它在 3 天前工作，但我不知道我做了什么。我将代码 sn-ps 放在这里。提前感谢您的帮助。

我的小服务程序

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         
listBook(request, response);
}private void listBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException  {
    List<Book> books = book.getAllBooks();
    request.setAttribute("books", books);
    this.getServletContext().getRequestDispatcher(VUE_LISTBOOK).forward(request, response);

}

BookImpl：

@Override
public List<Book> getAllbooks() {
    Connection c = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    List<Book> books = new ArrayList<Book>();
    try {
        c = MysqlDaoFactory.getInstance().getConnection();
        ps = c.prepareStatement(SQL_SELECT);
        rs = ps.executeQuery();
         
        while (rs.next()) {
            Book book = new Book();
            book.setIdBook(rs.getInt("id"));
            book.setTitle(rs.getString("title"));
            book.setIsbn(rs.getString("isbn"));
            book.setEdition(rs.getString("edition"));
            book.setPublicationDate(rs.getDate("publicationDate"));
            book.setResume(rs.getString("resume"));
            book.setNbPage(rs.getInt("nbPage"));
            book.setBarcode(rs.getString("barcode"));
            book.setImage(rs.getString("image"));      
            book.setCategory(category.findById(rs.getInt("id")));

            books.add(book);
            }
    }

CategoryImpl ：

private Category findById(String sql, int id) {
    Connection connection = null;
    Category category=null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    try {
        connection = MysqlDaoFactory.getInstance().getConnection();
        ps = connection.prepareStatement("SELECT * from category where id=?");
        ps.setInt(1, id);
        rs = ps.executeQuery();
        if (rs.next()) {
            category = new Category();
            int id2 = Integer.parseInt(rs.getString("id"));
            String category1 = rs.getString("category");
            category.setId(id2);
            category.setCategory(category1);
             
           }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        MysqlConnectionFactory.closeConnection(connection);
        MysqlConnectionFactory.closeResultSet(rs);
    }
    return category;
}

}

JSP：

<c:forEach items="${books}" var="books">
                   <tr>
                       <th><c:out value="${books.idBook}"/></th>
                       <th><c:out value="${books.title}"/></th>
                       <th><c:out value="${books.isbn}"/></th>
                       <th><c:out value="${books.edition}"/></th>
                       <th><c:out value="${books.publicationDate}"/></th>
                       <th><c:out value="${books.resume}"/></th>
                       <th><c:out value="${books.barcode}"/></th>
                       <th><c:out value="${books.image}"/></th>
                       <th><c:out value="${books.category.category}"/></th>
                       
                                               
                   </tr>
               </c:forEach>

输出：

<!DOCTYPE html>

<!-- meta -->

<meta charset="utf-8">

                    <tr>

                        <th>test</th>

                        <th>test</th>

                        <th>test</th>

                        <th>test</th>

       <th>1111-05-05</th>

           <th>test</th>

       <th>test</th>

                        <th>test</th>

                        <th></th> ---> Empty

我认为问题来自“FindById”方法如果不清楚，请见谅

【问题讨论】：

标签： jsp servlets

【解决方案1】：

问题已经解决，我输入了错误的ID，我们可以关闭这个主题吗？

【讨论】：