在文本框中显示数据库列值 [英] Display database column value in a text box

问题描述

嘿朋友，



我正在尝试使用jsp，servlet，java和mysql进行在线图书馆系统。在我的系统中，通过文本框输入书籍ID并搜索书籍，然后在下一个文本框中显示该框的名称。我的问题是如何在文本框中显示db列值。值传递给jsp-> servlet-> service-> dao，反之亦然。但没有在第二个文本框中显示名称。

这里是我的系统代码。

Hey friends,

I'm trying to do a online library system using jsp, servlet, java and mysql. In my system im tring to enter a book id through a text box and search the book then display the name of the box in next text box.my problem is how to display a db column value in a text box. values are passing to jsp->servlet->service->dao and vice versa. but did not display the name in the 2nd text box.
here my code of my system.

<div id="page">
            <form name="input" action="book" method="post">
                Book Id   :       <input type="text" name="txtBid" class="resizedTextbox"><br><br>
                                   
                <input type="submit" value="Search Book" onclick= <a href="main/Servelet"</a>      
                <input type="hidden" name="operation" value="searchBookbtn"><br><br>	
                Book Name : <input type="text" name="txtName" class="resizedTextbox"><br><br>
                                   
                <input type="submit" value="Delete Book" onclick= <a href="main/Servelet"</a>
                <input type="hidden" name="operation" value="deleteBookbtn">	
                <input type="submit" value="Cancel/Clear" onclick= <a href="main/Servelet"</a>
                <p><%=request.getAttribute("deleteBookMsg") %></p>
            </form>
                <br><br><br><br><br><br><br><br><br><br><br>
        </div>

< br $>
servlet

servlet

private void searchBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        System.out.println("Inside searchBook");
        book b =new book();
        bookService bs = new bookServiceImpl();
        
        String b_id=request.getParameter("txtBid");
        String b_name=request.getParameter("txtName");
        
        b.setB_id(b_id);
        b.setB_title(b_name);
        
        System.out.println(b_id);
        if(bs.searchbook(b)){
            String message = "Click Delete button to delete the book detail";
            request.setAttribute("deleteBookMsg", message);
            request.setAttribute("txtName",b); 
        }else{
           String message = "Book does not Exist";
 	   request.setAttribute("deleteBookMsg", message);
        }
        RequestDispatcher rd = getServletContext().getRequestDispatcher("/deleteBook.jsp");
        rd.forward(request, response);
    }

服务层

service layer

public boolean searchbook(book b) {
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        System.out.println("Inside bs.searchbook");
        boolean book_result=true;
        bookDAO bd = new bookDAOImpl();
        System.out.println("===Inside bs.searchbook");
        book bk =bd.search(b);
        if(bk==null){
             System.out.println("....");
             System.out.println(book_result);
             book_result=false;     
        }return book_result; 
     }

dao

dao

public book search(book b) {
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        System.out.println("Inside book search");
        book b_result = null;
        Connection conn= null;
        PreparedStatement ptmt= null;
        ResultSet rset = null;
        try{ 
            conn= getConnection();             
            String queryString = "SELECT * FROM book WHERE b_id=?";
            ptmt = conn.prepareStatement(queryString);
            ptmt.setString(1, b.getB_id());
            System.out.println(b.getB_id());
            rset = ptmt.executeQuery();
            
            System.out.println(rset.first()); 
            if (rset.first()){
                System.out.println(rset.first());
                b_result = new book();
                b_result.setB_title(rset.getString(String.valueOf("b_title")));
                b_result.setB_suplier(rset.getString(String.valueOf("b_supplier")));
                b_result.setB_publisher(rset.getString(String.valueOf("b_publisher")));
                return b_result;
            }    
        } catch (SQLException ex) {
              ex.printStackTrace();
        }  
        finally {
                try {
                    ptmt.close();
                    conn.close();
                } catch (SQLException ex) {
                    ex.printStackTrace();
                }
        }System.out.println("======");
        System.out.println(b_result);
        return b_result;	
    }

推荐答案

当你的servlet返回到jsp时，你需要在jsp中引用txtName请求属性，例如：

you need to reference the txtName request attribute in the jsp when your servlet returns to that jsp e.g.

<input type="text" name="txtName" value="<%=request.getAttribute('txtName')%>" class="resizedTextbox">

只要确保你处理案件wh当首次加载jsp时，即在调用servlet之前，该属性中的值为null。比使用这些java scriptlet更好的解决方案是使用taglib库。 GoogleJSLT核心代码用于示例和教程。

Just make sure you handle the case where the value in that attribute is null when the jsp is first loaded i.e. before the servlet is invoked. A better solution than using these java scriptlets is to use a taglib library. Google "JSLT core tags" for examples and tutorials.

我创建了一个简化的项目版本，并将eclipse项目压缩到此URL：http://www.filedropper.com/librarysearch [ ^ ]。以此为基础并添加您的搜索等。您的代码中存在许多问题，例如onclick处理程序不能有标签。我建议你使用struts或spring mvc，因为使用jsps和servlet不是最好的解决方案

I've created a simplied version of your project and zipped the eclipse project to this URL: http://www.filedropper.com/librarysearch[^]. Use this as a base and add your search etc. There are many problems in your code e.g. the onclick handler cannot have tags. I would suggest you use struts or spring mvc as using jsps and servlets is not the best solution

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