Java 从模型到Servlet再到JSP选项列表获取信息

我有一个模型，里面有一个arraylist。我还有一个servlet需要从模型中提取。最后，JSP需要获取从servlet（控制器）检索到的信息，并为选择列表生成选项。我不明白为什么这根本不起作用。我刚刚进入jsp的，所以任何帮助将不胜感激

我有下面的3页和stacktrace

所建议的任何有助于未来发展的变化也会有所帮助。我非常开放，希望用正确的方式来做这件事

模型（具有arraylist）

包edu.witc.Assignment03.model；
导入java.util.ArrayList；
导入java.util.List；
公共阶级国家{
私有列表状态=新的ArrayList（）{
添加（“阿拉巴马州”）；
添加（“阿拉斯加”）；
添加（“亚利桑那州”）；
添加（“阿肯色州”）；
添加（“加利福尼亚”）；
添加（“科罗拉多”）；
添加（“康涅狄格州”）；
添加（“特拉华州”）；
添加（“佛罗里达”）；
添加（“格鲁吉亚”）；
添加（“夏威夷”）；
添加（“爱达荷州”）；
添加（“伊利诺伊州”）；
添加（“印第安纳州”）；
添加（“爱荷华州”）；
添加（“堪萨斯”）；
添加（“肯塔基州”）；
添加（“路易斯安那州”）；
添加（“缅因州”）；
添加（“马里兰州”）；
添加（“马萨诸塞州”）；
添加（“密歇根”）；
添加（“明尼苏达州”）；
添加（“密西西比”）；
添加（“密苏里州”）；
添加（“蒙大拿”）；
添加（“内布拉斯加州”）；
添加（“内华达州”）；
添加（“新罕布什尔州”）；
添加（“新泽西”）；
添加（“新墨西哥州”）；
添加（“纽约”）；
添加（“北卡罗来纳州”）；
添加（“北达科他州”）；
添加（“俄亥俄州”）；
添加（“俄克拉荷马州”）；
添加（“俄勒冈州”）；
添加（“宾夕法尼亚州”）；
添加（“罗德岛”）；
添加（“南卡罗来纳州”）；
添加（“南达科他州”）；
添加（“田纳西州”）；
添加（“德克萨斯州”）；
添加（“犹他州”）；
添加（“佛蒙特州”）；
添加（“弗吉尼亚”）；
添加（“华盛顿”）；
添加（“西弗吉尼亚”）；
添加（“威斯康星州”）；
添加（“怀俄明州”）；
}
公共列表getStates（）{
把这封信寄回美国；
}
}

控制器（Servlet）

包edu.witc.Assignment03.controller；
导入java.io.IOException；
导入java.util.ArrayList；
导入java.util.List；
导入javax.servlet.*；
导入javax.servlet.annotation.WebServlet；
导入javax.servlet.http.HttpServlet；
导入javax.servlet.http.HttpServletRequest；
导入javax.servlet.http.HttpServletResponse；
//导入javax.servlet.annotation.WebServlet；
//导入javax.servlet.http.HttpServlet；
//导入javax.servlet.http.HttpServletRequest；
//导入javax.servlet.http.HttpServletResponse；
导入edu.witc.Assignment03.model.Customer；
导入edu.witc.Assignment03.model.Phone；
导入edu.witc.Assignment03.model.States；
/*
*不是线程安全的。仅供说明之用
*/
@WebServlet（name=“CustomerServlet”，urlPatterns={
“/customerManagement”}）
公共类CustomerServlet扩展了HttpServlet{
私有静态最终长serialVersionUID=-20L；
private edu.witc.Assignment03.model.States=新州（）；
private List customers=new ArrayList（）；
私有void addCustomer（HttpServletResponse，HttpServletRequest）//重定向到索引
抛出IOException、ServletException{
字符串url=“/customerManagement.jsp”；
request.setAttribute（“客户”，客户）；
getRequestDispatcher（url）.forward（请求，响应）；
}
私有void editCustomer（HttpServletResponse，HttpServletRequest）//重定向到索引
抛出IOException、ServletException{
字符串url=“/customerManagement.jsp”；
request.setAttribute（“客户”，客户）；
getRequestDispatcher（url）.forward（请求，响应）；
}
私有void sendCustomerList（HttpServletResponse，HttpServletRequest）//重定向到索引
抛出IOException、ServletException{
字符串url=“/index.jsp”；
request.setAttribute（“客户”，客户）；
getRequestDispatcher（url）.forward（请求，响应）；
}
私人客户getCustomer（int customerId）{
用于（客户：客户）{
if（customer.getCustomerId（）==customerId）{
退货客户；
}
}
返回null；
}
私有void sendEditCustomerForm（HttpServletRequest请求，
HttpServletResponse响应）引发IOException，ServletException{
字符串url=“/customerManagement.jsp”；
request.setAttribute（“客户”，客户）；
getRequestDispatcher（url）.forward（请求，响应）；
}
公共无效数据集（HttpServletRequest请求，
HttpServletResponse（响应）
抛出ServletException、IOException{
字符串uri=request.getRequestURI（）；
if（uri.endsWith（“/customer”））{
sendCustomerList（响应、请求）；
}else if（uri.endsWith（“/editCustomer”））{
SendEditCustomPerform（请求、响应）；
}
setAttribute（“states”，states）；
}
public void doPost（HttpServletRequest请求，
HttpServletResponse（响应）
抛出ServletException、IOException{
//更新客户
int customerId=0；
试一试{
客户ID=
Integer.parseInt（request.getParameter（“id”）；
}捕获（数字格式）{
}
Customer=getCustomer（customerId）；
如果（客户！=null）{
customer.setFirstName（request.getParameter（“firstName”）；
customer.setLastName（request.getParameter（“lastName”）；
customer.setEmail（request.getPar
package edu.witc.Assignment03.model;

import java.util.ArrayList;
import java.util.List;

public class States {

    private List<String> states = new ArrayList<>();{

    states.add("Alabama");
    states.add("Alaska"); 
    states.add("Arizona"); 
    states.add("Arkansas"); 
    states.add("California"); 
    states.add("Colorado"); 
    states.add("Connecticut"); 
    states.add("Delaware"); 
    states.add("Florida"); 
    states.add("Georgia"); 
    states.add("Hawaii"); 
    states.add("Idaho"); 
    states.add("Illinois"); 
    states.add("Indiana"); 
    states.add("Iowa"); 
    states.add("Kansas"); 
    states.add("Kentucky"); 
    states.add("Louisiana"); 
    states.add("Maine"); 
    states.add("Maryland"); 
    states.add("Massachusetts"); 
    states.add("Michigan"); 
    states.add("Minnesota"); 
    states.add("Mississippi"); 
    states.add("Missouri"); 
    states.add("Montana"); 
    states.add("Nebraska"); 
    states.add("Nevada"); 
    states.add("New Hampshire"); 
    states.add("New Jersey"); 
    states.add("New Mexico"); 
    states.add("New York"); 
    states.add("North Carolina"); 
    states.add("North Dakota"); 
    states.add("Ohio"); 
    states.add("Oklahoma"); 
    states.add("Oregon"); 
    states.add("Pennsylvania"); 
    states.add("Rhode Island"); 
    states.add("South Carolina"); 
    states.add("South Dakota"); 
    states.add("Tennessee"); 
    states.add("Texas"); 
    states.add("Utah"); 
    states.add("Vermont"); 
    states.add("Virginia"); 
    states.add("Washington"); 
    states.add("West Virginia"); 
    states.add("Wisconsin"); 
    states.add("Wyoming");
    }

    public List<String> getStates(){
        return this.states;
    }
}

package edu.witc.Assignment03.controller;
import java.io.IOException;
import java.util.ArrayList;
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 edu.witc.Assignment03.model.Customer;
import edu.witc.Assignment03.model.Phone;
import edu.witc.Assignment03.model.States;

/*
 * Not thread-safe. For illustration purpose only
 */
@WebServlet(name = "CustomerServlet", urlPatterns = { 
        "/customerManagement"})
public class CustomerServlet extends HttpServlet {
    private static final long serialVersionUID = -20L;

    private edu.witc.Assignment03.model.States states = new States();
    private List<edu.witc.Assignment03.model.Customer> customers = new ArrayList<Customer>();



 private void addCustomer(HttpServletResponse response, HttpServletRequest request)//redirect to index
           throws IOException, ServletException {
    String url = "/customerManagement.jsp";
        request.setAttribute("customers", customers);
        request.getRequestDispatcher(url).forward(request,response);
    }

    private void editCustomer(HttpServletResponse response, HttpServletRequest request)//redirect to index
           throws IOException, ServletException {
        String url = "/customerManagement.jsp";
        request.setAttribute("customers", customers);
    request.getRequestDispatcher(url).forward(request,response);
    }

    private void sendCustomerList(HttpServletResponse response, HttpServletRequest request)//redirect to index
            throws IOException, ServletException {
        String url = "/index.jsp";
        request.setAttribute("customers", customers);
        request.getRequestDispatcher(url).forward(request,response);




    }

    private Customer getCustomer(int customerId) {
        for (Customer customer : customers) {
            if (customer.getCustomerId() == customerId) {
                return customer;
            }
        }
        return null;
    }



    private void sendEditCustomerForm(HttpServletRequest request, 
            HttpServletResponse response) throws IOException, ServletException {

        String url = "/customerManagement.jsp";
        request.setAttribute("customers", customers);
        request.getRequestDispatcher(url).forward(request,response);
    }


    public void doGet(HttpServletRequest request, 
            HttpServletResponse response)
            throws ServletException, IOException {
        String uri = request.getRequestURI();
        if (uri.endsWith("/customer")) {
            sendCustomerList(response, request);
        } else if (uri.endsWith("/editCustomer")) {
            sendEditCustomerForm(request, response);
        }

        request.setAttribute("states", states);

    }



    public void doPost(HttpServletRequest request, 
            HttpServletResponse response)
            throws ServletException, IOException {
        // update customer
        int customerId = 0;
        try {
            customerId = 
                    Integer.parseInt(request.getParameter("id"));
        } catch (NumberFormatException e) {
        }
        Customer customer = getCustomer(customerId);
        if (customer != null) {
            customer.setFirstName(request.getParameter("firstName"));
            customer.setLastName(request.getParameter("lastName"));
            customer.setEmail(request.getParameter("email"));
            customer.setPhone(request.getParameter("phone"));
            customer.setAddress(request.getParameter("address"));
            customer.setCity(request.getParameter("city"));

            customer.setZip(request.getParameter("zip"));
        }
        addCustomer(response, request);
    }
}

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
    <%@ page import="java.util.ArrayList" %>
<!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>Customer Management</title>
</head>
<body>
    <form action="/CustomerServlet" method="post">
        First Name:<br>
        <input type="text" name="firstName"/><br>
        Last Name:<br>
        <input type="text" name="lastName"/><br>
        Email:<br>
        <input type="text" name="email"/><br>
        Phone:<br>
        <input type="text" name="phone"/><br>
        Phone Type:<br>

        Street Address:<br>
        <input type="text" name="streetAddress"/><br>
        Apartment Number:<br>
        <input type="text" name="apartmentNumber"/><br>
        City:<br>
        <input type="text" name="city"/><br>


        State:<br>
        <select>
            <%
            edu.witc.Assignment03.model.States states = request.getAttribute("states");
            if(states!=null){   
            for (String state : states.getStates()) { 
                   out.println("<option>"+state+"</option>");
               }
             }else{
                 System.out.print("states is null");
             }
             %>
        </select><br>

        <input type="submit" value="submit">
        </form>
</body>
</html>

Mar 30, 2014 8:17:13 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [jsp] in context with path [/Justin_EJ_Assignment03_15400579] threw exception [Unable to compile class for JSP: 

An error occurred at line: 33 in the jsp file: /customerManagement.jsp
Type mismatch: cannot convert from Object to States
30:         State:<br>
31:         <select>
32:             <%
33:             edu.witc.Assignment03.model.States states = request.getAttribute("states");
34:             if(states!=null){   
35:             for (String state : states.getStates()) { 
36:                    out.println("<option>"+state+"</option>");


Stacktrace:] with root cause
org.apache.jasper.JasperException: Unable to compile class for JSP: 

An error occurred at line: 33 in the jsp file: /customerManagement.jsp
Type mismatch: cannot convert from Object to States
30:         State:<br>
31:         <select>
32:             <%
33:             edu.witc.Assignment03.model.States states = request.getAttribute("states");
34:             if(states!=null){   
35:             for (String state : states.getStates()) { 
36:                    out.println("<option>"+state+"</option>");


Stacktrace:
    at org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:103)
    at org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:366)
    at org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:468)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:378)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)
    at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:657)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

<c:forEach var="state" items="states">
        <option>
            <c:out value="${person.name}" />
        </option>
</c:forEach>