Question

我试图使用MVC编写Web应用程序。我有bean，jsp和servlets。我想要实现的目标：用户将能够在表格中创建（购物）列表。该表将有一个显示创建日期的thead。然后它将创建包含3列的行（1-id，2-name of product，3- a＆＃39; buy＆＃39; link）。当用户点击“已购买”时，链接，它将从3列中删除链接，并将产品的名称变为绿色。表外的某个地方会有另一个链接，让用户创建一个新列表。如果存在现有列表，则表示尚未购买的产品＆＃39;然而，会自动转到新列表。一旦用户点击＆＃34;创建新列表＆＃34;链接，它只显示新列表（如果有的话，还有未购买的产品）。

我目前遇到的问题是：只有点击购买的链接才会显示日期，但点击后不会将文字变为绿色或删除＆＃34;已购买的＆＃34;链接。

这是我的代码，任何帮助将不胜感激。谢谢。

Item.java

import java.text.Format;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Item {
//property names
String name;
Integer id;
boolean available = true;
Format formatter = new SimpleDateFormat("MM/dd/yyyy");
String today = formatter.format(new Date());

public Item(Integer id, String name, boolean available){
    this.id = id;
    this.name = name;
    this.available = available; 
}

public String getToday() {
    return today;
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public boolean isAvailable() {
    return available;
}

public void setAvailable(boolean available) {
    this.available = available;
}
}

DisplayList.jsp

<?xml version="1.0" encoding="ISO-8859-1" ?>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
<title>Grocery List</title>
</head>
<body>

<h1>Grocery List</h1>

<table border='1'>
<tr><th colspan='3'>${entry.today}</th></tr>

<c:forEach items="${entries}" var="entry">
<tr>
<td>${entry.id}</td>
<c:choose>
    <c:when test="${entry.available != false }">
        <td>${entry.name}</td>
        <td><a href="Bought?id=${entry.id}">Bought</a></td>
    </c:when>
    <c:when test="${entry.available != true }">
        <td style="color:green;" >${entry.name}</td>
        <td></td>
    </c:when>
</c:choose>
</tr>
</c:forEach>
<tr>
<form action="Groceries" method="post">
<td colspan='2'><input type="text" name="product" /></td>
<td><input type="submit" name="add" value="Add" /></td>
<p><input type="button" name="new" value="New List" /></p>
</form>
</tr>
</table>
</body>
</html>

Groceries.java

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/Groceries")
public class Groceries extends HttpServlet {
private static final long serialVersionUID = 1L;

int y = 3;

public Groceries() {
    super();
}

public void init(ServletConfig config) throws ServletException {
    super.init( config );
    List<Item> entries = new ArrayList<Item>();
    entries.add( new Item(1, "Milk", true) );
    entries.add( new Item(2, "Soda", true) );

    getServletContext().setAttribute( "entries", entries );

}

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

    request.getRequestDispatcher("/WEB-INF/DisplayList.jsp").forward(request, response);
}

@SuppressWarnings("unchecked")
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    String name = request.getParameter("product");
    Item entry = new Item(y, name, true);
    y++;

    List<Item> entries = (List<Item>) getServletContext().getAttribute("entries");
    entries.add( entry );
    response.sendRedirect("Groceries");

}

}

Bought.java

import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/Bought")
public class Bought extends HttpServlet {
private static final long serialVersionUID = 1L;

public Bought() {
    super();
}

/**
 * Given an id, retrieve the List entry.
 */
@SuppressWarnings("unchecked")
private Item getEntry( Integer id )
{
    List<Item> entries = (List<Item>) getServletContext().getAttribute("entries" );

    for( Item entry : entries )
        if( entry.getId().equals( id ) ) 
            return entry;

    return null;
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // get the entry to be edited
    Integer id = Integer.valueOf( request.getParameter( "id" ) );
    Item entry = getEntry( id );

    // pass the entry to jsp using request scope
    request.setAttribute( "entry", entry );
    request.getRequestDispatcher( "/WEB-INF/DisplayList.jsp" ).forward(request, response );
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // get the entry to be edited
    Integer id = Integer.valueOf( request.getParameter( "id" ) );
    Item entry = getEntry( id );

    // change the entry based on user input
    entry.setAvailable(true);

    // send the user back to the guest book page
    request.getRequestDispatcher( "/WEB-INF/DisplayList.jsp" ).forward(request, response );
}

}

Answer 1

以下链接应该替换为在JSP中映射servlet。

<a href="<c:url value='/Bought'><c:param name='id' value='${entry.id}'/></c:url>">Bought</a>

在doGet方法中，您需要设置可用性条件

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // get the entry to be edited
    Integer id = Integer.valueOf( request.getParameter( "id" ) );
    Item entry = getEntry( id );
    entry.setAvailable(false);
    // pass the entry to jsp using request scope
    request.setAttribute( "entry", entry );
    request.getRequestDispatcher( "/WEB-INF/DisplayList.jsp" ).forward(request, response );
}

使用jsps更改视图（来自MVC）

1 个答案: