java - 将从数据库检索的数据从servlet显示到jsp文件

Question

当用户单击个人资料链接时，我尝试显示用户个人资料详细信息。我正在使用 eclipse 。同样采用mvc架构。没有发生错误，但数据没有显示在 jsp 文件中。

CustomerProfileController servlet

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    String name = request.getParameter("name");
    CustomerViewQuery cvq = new CustomerViewQuery(name);

    try {
        List<Customer> customers = cvq.list();
        request.setAttribute("customers", customers); // Will be available as ${products} in JSP
        request.getRequestDispatcher("CustomerProfile.jsp").forward(request, response);
    } catch (SQLException e) {
        throw new ServletException("Cannot obtain vehicles from DB", e);
    }
}

CustomerView查询文件

package dbhelpers;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import models.Customer;


public class CustomerViewQuery {
    DBConnection databaseCon = new DBConnection();
    String uName;
    public CustomerViewQuery(String name) {
        this.uName = name;
    }

    public List<Customer> list() throws SQLException {
        List<Customer> customers = new ArrayList<Customer>();
        try (
            Connection con = databaseCon.dbconnect();
            PreparedStatement pst = con.prepareStatement("SELECT * FROM customers WHERE username='\"+uName+\"'");
            ResultSet resultSet = pst.executeQuery();
        ) {
            while (resultSet.next()) {
                Customer customer = new Customer();
                customer.setId(resultSet.getInt("id"));
                customer.setName(resultSet.getString("name"));
                customer.setEmail(resultSet.getString("email"));
                customer.setAddress(resultSet.getString("address"));
                customer.setSex(resultSet.getString("sex"));
                customer.setBday(resultSet.getString("bday"));
                customer.setTelephone(resultSet.getString("telephone"));
                customer.setUsername(resultSet.getString("username"));
                customer.setPassword(resultSet.getString("password"));
                customers.add(customer);
            }
        }catch(SQLException e) {
            e.printStackTrace();
        }

        return customers;
    }

}

Getter 和 Setter 位于 Customer.java 文件中

我没有收到任何错误，但 CustomerProfile.jsp 文件中也没有显示任何内容。这是代码

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<c:forEach items="${customers}" var="customer">

</c:forEach>

<div class="container mt-5"><br>
    <form role="form" action="CustomerController" data-toggle="validator" method="post" id="registerForm">
        <div class="form-group row">
            <label for="name" class="col-sm-2 col-form-label">Name</label>
            <div class="col-sm-10">
              <input type="text" name="name" value="${customer.name}" placeholder="Name">
            </div>
          </div>
          <div class="form-group row">
            <label for="email" class="col-sm-2 col-form-label">Email</label>
            <div class="col-sm-10">
              <input type="email" name="email" value="${customer.email}" placeholder="Email">
            </div>
          </div>
          <div class="form-group row">
            <label for="email" class="col-sm-2 col-form-label">Address</label>
            <div class="col-sm-10">
              <input type="text" name="address" value="${customer.address}" placeholder="Address">
            </div>
          </div>
          <div class="form-group row">
            <label for="sex" class="col-sm-2 col-form-label">Sex</label>
            <div class="col-sm-10">
              <div class="custom-control custom-radio custom-control-inline">
                  <input name="sex" type="radio" value="${customer.sex}" id="customRadioInline1" class="custom-control-input">
                  <label class="custom-control-label" for="customRadioInline1">Male</label>
                </div>
                <div class="custom-control custom-radio custom-control-inline">
                  <input name="sex" type="radio" value="${customer.sex}" id="customRadioInline2" class="custom-control-input">
                  <label class="custom-control-label" for="customRadioInline2">Female</label>
              </div>
            </div>
          </div>
           <div class="form-group row">
            <label for="birthdate" class="col-sm-2 col-form-label">Birthdate</label>
            <div class="col-sm-10">
              <input type="date" name="bday" value="${customer.bday}" placeholder="Birthdate" required>
            </div>
          </div>
          <div class="form-group row">
            <label for="telephone" class="col-sm-2 col-form-label">Telephone</label>
            <div class="col-sm-10">
              <input type="text" name="tele" value="${customer.telephone}" placeholder="Telephone">
            </div>
          </div>
          <div class="form-group row">
            <label for="username" class="col-sm-2 col-form-label">Username</label>
            <div class="col-sm-10">
              <input type="text" name="username" value="${customer.username}" placeholder="Username">
            </div>
          </div>
          <div class="form-group row">
            <label for="passowrd" class="col-sm-2 col-form-label">Password</label>
            <div class="col-sm-10">
              <input type="password" name="password" value="${customer.password}" id="inputPassword" placeholder="Password" data-minlength="6">
              <div class="invalid-feedback">
                Please provide a valid city.
              </div>
            </div>
          </div>
        <button type="submit" class="btn btn-primary btn-block btn-large">Sign me up.</button>
    </form><br>
</div>

Answer 1

在这里我用你的代码改变了一些东西。现在应该可以了。让我知道。

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

String name = request.getParameter("name");

CustomerViewQuery cvq = new CustomerViewQuery();

 try {

    List<Customer> customers = cvq.list(name);
    request.setAttribute("customers", customers); 
    request.getRequestDispatcher("CustomerProfile.jsp").forward(request, response);

     } catch (SQLException e) {
    throw new ServletException("Cannot obtain vehicles from DB", e);
     }
}

这里也有一些变化:

public class CustomerViewQuery {

   public List<Customer> list(String name) throws SQLException {

    List<Customer> customers = new ArrayList<Customer>();
     //get connection like this
    try(Connection con = DBConnection.dbconnect()) {

        PreparedStatement pst = con.prepareStatement("SELECT * FROM customers WHERE username=?;");
        pst.setString(1, name); //set name like this (The '1' means first occurance of a question mark '?')
        ResultSet resultSet = pst.executeQuery();

        while (resultSet.next()) {
            Customer customer = new Customer();
            customer.setId(resultSet.getInt("id"));
            customer.setName(resultSet.getString("name"));
            customer.setEmail(resultSet.getString("email"));
            customer.setAddress(resultSet.getString("address"));
            customer.setSex(resultSet.getString("sex"));
            customer.setBday(resultSet.getString("bday"));
            customer.setTelephone(resultSet.getString("telephone"));
            customer.setUsername(resultSet.getString("username"));
            customer.setPassword(resultSet.getString("password"));
            customers.add(customer);
        }
    }catch(SQLException e) {
        e.printStackTrace();
    }

    return customers;
   }

}

您的 forEach JSTL 标记没有迭代任何内容...

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>


<c:forEach items="${customers}" var="customer">

<div class="container mt-5"><br>
    <form role="form" action="CustomerController" data-toggle="validator" method="post" id="registerForm">
        <div class="form-group row">
            <label for="name" class="col-sm-2 col-form-label">Name</label>
            <div class="col-sm-10">
              <input type="text" name="name" value="${customer.name}" placeholder="Name">
            </div>
          </div>
          <div class="form-group row">
            <label for="email" class="col-sm-2 col-form-label">Email</label>
            <div class="col-sm-10">
              <input type="email" name="email" value="${customer.email}" placeholder="Email">
            </div>
          </div>
          <div class="form-group row">
            <label for="email" class="col-sm-2 col-form-label">Address</label>
            <div class="col-sm-10">
              <input type="text" name="address" value="${customer.address}" placeholder="Address">
            </div>
          </div>
          <div class="form-group row">
            <label for="sex" class="col-sm-2 col-form-label">Sex</label>
            <div class="col-sm-10">
              <div class="custom-control custom-radio custom-control-inline">
                  <input name="sex" type="radio" value="${customer.sex}" id="customRadioInline1" class="custom-control-input">
                  <label class="custom-control-label" for="customRadioInline1">Male</label>
                </div>
                <div class="custom-control custom-radio custom-control-inline">
                  <input name="sex" type="radio" value="${customer.sex}" id="customRadioInline2" class="custom-control-input">
                  <label class="custom-control-label" for="customRadioInline2">Female</label>
              </div>
            </div>
          </div>
           <div class="form-group row">
            <label for="birthdate" class="col-sm-2 col-form-label">Birthdate</label>
            <div class="col-sm-10">
              <input type="date" name="bday" value="${customer.bday}" placeholder="Birthdate" required>
            </div>
          </div>
          <div class="form-group row">
            <label for="telephone" class="col-sm-2 col-form-label">Telephone</label>
            <div class="col-sm-10">
              <input type="text" name="tele" value="${customer.telephone}" placeholder="Telephone">
            </div>
          </div>
          <div class="form-group row">
            <label for="username" class="col-sm-2 col-form-label">Username</label>
            <div class="col-sm-10">
              <input type="text" name="username" value="${customer.username}" placeholder="Username">
            </div>
          </div>
          <div class="form-group row">
            <label for="passowrd" class="col-sm-2 col-form-label">Password</label>
            <div class="col-sm-10">
              <input type="password" name="password" value="${customer.password}" id="inputPassword" placeholder="Password" data-minlength="6">
              <div class="invalid-feedback">
                Please provide a valid city.
              </div>
            </div>
          </div>
        <button type="submit" class="btn btn-primary btn-block btn-large">Sign me up.</button>
    </form><br>
</div>

</c:forEach>

编辑:以下是无需循环即可实现的方法:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

String name = request.getParameter("name");
CustomerViewQuery cvq = new CustomerViewQuery();

 try {
   //not list required this time, created a new method called 'getCustomer'
    Customer customer = cvq.getCustomer(name);
    request.setAttribute("customer", customer); 
    request.getRequestDispatcher("CustomerProfile.jsp").forward(request, response);

     } catch (SQLException e) {
    throw new ServletException("Cannot obtain vehicles from DB", e);
     }
}

CustomerViewQuery 类中名为“getCustomer”的新方法

public class CustomerViewQuery {


   public Customer getCustomer(String name) throws SQLException {

   Customer customer = new Customer();

    try(Connection con = DBConnection.dbconnect()) {

        PreparedStatement pst = con.prepareStatement("SELECT * FROM customers WHERE username=?;");
        pst.setString(1, name); //set name like this (The '1' means first occurance of a question mark '?')
        ResultSet resultSet = pst.executeQuery();

        while (resultSet.next()) {

            customer.setId(resultSet.getInt("id"));
            customer.setName(resultSet.getString("name"));
            customer.setEmail(resultSet.getString("email"));
            customer.setAddress(resultSet.getString("address"));
            customer.setSex(resultSet.getString("sex"));
            customer.setBday(resultSet.getString("bday"));
            customer.setTelephone(resultSet.getString("telephone"));
            customer.setUsername(resultSet.getString("username"));
            customer.setPassword(resultSet.getString("password"));

        }
    }catch(SQLException e) {
        e.printStackTrace();
    }

    return customer;
   }

}

除了删除了 JSTL forEach 标记(因为不再需要它)之外，此处没有任何更改。

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>


<div class="container mt-5"><br>
    <form role="form" action="CustomerController" data-toggle="validator" method="post" id="registerForm">
        <div class="form-group row">
            <label for="name" class="col-sm-2 col-form-label">Name</label>
            <div class="col-sm-10">
              <input type="text" name="name" value="${customer.name}" placeholder="Name">
            </div>
          </div>
          <div class="form-group row">
            <label for="email" class="col-sm-2 col-form-label">Email</label>
            <div class="col-sm-10">
              <input type="email" name="email" value="${customer.email}" placeholder="Email">
            </div>
          </div>
          <div class="form-group row">
            <label for="email" class="col-sm-2 col-form-label">Address</label>
            <div class="col-sm-10">
              <input type="text" name="address" value="${customer.address}" placeholder="Address">
            </div>
          </div>
          <div class="form-group row">
            <label for="sex" class="col-sm-2 col-form-label">Sex</label>
            <div class="col-sm-10">
              <div class="custom-control custom-radio custom-control-inline">
                  <input name="sex" type="radio" value="${customer.sex}" id="customRadioInline1" class="custom-control-input">
                  <label class="custom-control-label" for="customRadioInline1">Male</label>
                </div>
                <div class="custom-control custom-radio custom-control-inline">
                  <input name="sex" type="radio" value="${customer.sex}" id="customRadioInline2" class="custom-control-input">
                  <label class="custom-control-label" for="customRadioInline2">Female</label>
              </div>
            </div>
          </div>
           <div class="form-group row">
            <label for="birthdate" class="col-sm-2 col-form-label">Birthdate</label>
            <div class="col-sm-10">
              <input type="date" name="bday" value="${customer.bday}" placeholder="Birthdate" required>
            </div>
          </div>
          <div class="form-group row">
            <label for="telephone" class="col-sm-2 col-form-label">Telephone</label>
            <div class="col-sm-10">
              <input type="text" name="tele" value="${customer.telephone}" placeholder="Telephone">
            </div>
          </div>
          <div class="form-group row">
            <label for="username" class="col-sm-2 col-form-label">Username</label>
            <div class="col-sm-10">
              <input type="text" name="username" value="${customer.username}" placeholder="Username">
            </div>
          </div>
          <div class="form-group row">
            <label for="passowrd" class="col-sm-2 col-form-label">Password</label>
            <div class="col-sm-10">
              <input type="password" name="password" value="${customer.password}" id="inputPassword" placeholder="Password" data-minlength="6">
              <div class="invalid-feedback">
                Please provide a valid city.
              </div>
            </div>
          </div>
        <button type="submit" class="btn btn-primary btn-block btn-large">Sign me up.</button>
    </form><br>
</div>