当我加载index.jsp时，我想将所有客户加载到页面上。出于某种原因，我无法让客户从数据库中显示出来。我假设我的servlet中的某个地方出错了。
下面是索引页面和servlet。
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ page import="java.util.ArrayList" %>
<%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql" %>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Add a Customer/Pet</title>
</head>
<body>
<h1>List of Customers</h1>
<form action="fetchDataServlet" method="get">
<c:forEach items="${sessionScope.customers}" var="customer" >
<ul>
<li>${customer.getFirstName()}</li>
</ul>
</c:forEach>
</form>
</body>
</html>
package edu.witc.Assignment05.controller;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//import javax.servlet.annotation.WebServlet;
//import javax.servlet.http.HttpServlet;
//import javax.servlet.http.HttpServletRequest;
//import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import edu.witc.Assignment05.model.Customer;
import edu.witc.Assignment05.model.CustomerDAO;
@WebServlet(description = "servlet to get act as controller between form and models", urlPatterns = { "/fetchDataServlet","/addCustomer","/addPet", "/customerManagement" })
public class FetchDataServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public FetchDataServlet() {
super();
}
private List<edu.witc.Assignment05.model.Customer> customers = new ArrayList<Customer>();
private void addCustomer(HttpServletResponse response, HttpServletRequest request)//redirect to form
throws IOException, ServletException {
String url = "/customerManagement.jsp";
//processRequest(request, response);
Customer customer = new Customer();
HttpSession session = request.getSession();
session.setAttribute("customer", customer);
request.getRequestDispatcher(url).forward(request,response);
}
private void addPet(HttpServletResponse response, HttpServletRequest request)//redirect to pet page
throws IOException, ServletException {
String url = "/pets.jsp";
request.getRequestDispatcher(url).forward(request,response);
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
request.setAttribute("customers", customers);
String url = "/index.jsp";
request.getRequestDispatcher(url).forward(request,response);
}
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
int customerId = 0;
Customer customer = new Customer();
if (customer != null) {
customerId = customers.size()+1;
customer.setCustomerId(customerId);
customer.setFirstName(request.getParameter("firstName"));
customer.setLastName(request.getParameter("lastName"));
customer.setEmailAddress(request.getParameter("email"));
customer.setPhoneNumber(request.getParameter("phone"));
customers.add(customer);
}
}
}
package edu.witc.Assignment05.model;
public class Customer {
int customerId = 0;
String firstName = "";
String lastName = "";
boolean customerIsActive = true;
int emailId = 0;
String emailAddress = "";
int emailUnitId = 0;
int phoneId = 0;
int phoneUnitId = 0;
String phoneNumber = "";
public Customer(){
}
public Customer(int customerId, String firstName, String lastName,
boolean customerIsActive, int emailId, String emailAddress,
int emailUnitId, int phoneId, int phoneUnitId, String phoneNumber){
this.customerId = customerId;
this.firstName = firstName;
this.lastName = lastName;
this.customerIsActive = customerIsActive;
this.emailId = emailId;
this.emailAddress = emailAddress;
this.emailUnitId = emailUnitId;
this.phoneId = phoneId;
this.phoneUnitId = phoneUnitId;
this.phoneNumber = phoneNumber;
}
public int getCustomerId() {
return customerId;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
public boolean getCustomerIsActive(){
return customerIsActive;
}
public int getEmailId(){
return emailId;
}
public String getEmailAddress(){
return emailAddress;
}
public int getEmailUnitId(){
return emailUnitId;
}
public int getPhoneId(){
return phoneId;
}
public int getPhoneUnitId(){
return phoneUnitId;
}
public String getPhoneNumber(){
return phoneNumber;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public void setCustomerIsActive(boolean customerIsActive) {
this.customerIsActive = customerIsActive;
}
public void setEmailId(int emailId) {
this.emailId = emailId;
}
public void setEmailAddress(String emailAddress) {
this.emailAddress = emailAddress;
}
public void setEmailUnitId(int emailUnitId) {
this.emailUnitId = emailUnitId;
}
public void setPhoneId(int phoneId) {
this.phoneId = phoneId;
}
public void setPhoneUnitId(int phoneUnitId) {
this.phoneUnitId = phoneUnitId;
}
public void setPhoneNumber(String phoneNumber) {
this.phoneNumber = phoneNumber;
}
public void setCustomerId(int customerId) {
this.customerId = customerId;
}
}
package edu.witc.Assignment05.model;
import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collection;
public class CustomerDAO<T> {
static final String DATABASE_URL =
"jdbc:jtds:sqlserver://localhost/A1Kennel;instance=sqlexpress";
private GenericClass<Customer>myCustomers = new GenericClass<>();
public CustomerDAO() throws ClassNotFoundException
{}
public Collection<T> getData() throws ClassNotFoundException
{ //Public method that can be called from the controller to get data
Collection<T> customerList = null;
customerList = fetchData();
return customerList;
}
@SuppressWarnings("unchecked")
private Collection<T> fetchData() throws ClassNotFoundException
{ //With a little tweaking, this method could be used to return any
//collection from the database
//ResultSet rs = null;
String myProc = "{Call FetchCustomer_All()}";
Customer customer = null;
Collection<T>allCustomers = new ArrayList<>();
CallableStatement procCall = null;
Connection conn = null;
try
{
Class.forName("net.sourceforge.jtds.jdbc.Driver");
conn = DriverManager.getConnection(DATABASE_URL,"","");
procCall = conn.prepareCall(myProc);
ResultSet rs = procCall.executeQuery();
if(rs != null)
{
while(rs.next())
{
//build an object
customer = new Customer(rs.getInt("customerId"), rs.getString("firstName"), rs.getString("lastName"),
rs.getBoolean("customerIsActive"), rs.getInt("emailId"), rs.getString("emailAddress"),
rs.getInt("emailUnitId"), rs.getInt("phoneId"), rs.getInt("phoneUnitId"), rs.getString("phoneNumber"));
myCustomers.addItem(customer);
}
allCustomers = (Collection<T>) myCustomers.getCollection();
}
}
catch(SQLException badSQL)
{
System.out.print(badSQL.getMessage());
}
finally{
try
{
procCall.close();
conn.close();
}
catch(Exception ex)
{
ex.getMessage();
}
}
return allCustomers;
}
}
答案 0 :(得分：0)
你需要：
doGet方法中：
这是如何实施doGet方法的框架：
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
CustomerService customerService = new CustomerService();
//assuming this method connects to database using a database connection pool
//and retrieves the results through JDBC using ResultSet
List<Customer> customers = customerService.findAllCustomers();
//store the data in request attribute
request.setAttribute("customers", customers);
//forward to the desired view:
String url = "/customerManagement.jsp";
request.getRequestDispatcher(url).forward(request,response);
}
除此之外，您应该知道 Servlet上没有任何状态。这将导致并发问题，如下所述：How do servlets work? Instantiation, sessions, shared variables and multithreading。这意味着，从Servlet（以及任何非List<edu.witc.Assignment05.model.Customer> customers字段或任何非托管资源）中删除final static字段。