老师帮忙看一下是哪里出问题了

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老师帮忙看一下是哪里出问题了

来源：6-2 项目作业

J_DP

2020-07-03 07:04:27

import java.util.ArrayList;

import java.util.List;

import com.imooc.domain.Category;

import com.imooc.web.service.CategoryService;

public class CategoryServiceImpl implements CategoryService {

private static final List<Category> categoryDb = new ArrayList<Category>();

@Override

public void addCategory(String categoryId,String categoryName) {

Category cate = new Category(categoryId,categoryName);

categoryDb.add(cate);

System.out.println(categoryDb);

}

@Override

public void deleteCatgory(String categoryId) {

for(Category category:categoryDb) {

if(category.getCategoryId().equals(categoryId)) {

categoryDb.remove(category);

break;

}

}

}

@Override

public List<Category> getCategoryDb() {

System.out.println(categoryDb);

return categoryDb;

}

}

package com.imooc.servlet;

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;

import com.imooc.domain.Category;

import com.imooc.web.service.CategoryService;

import com.imooc.web.service.impl.CategoryServiceImpl;

@WebServlet("/AddCategoryServlet")

public class AddCatgoryServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

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

// 接收数据

request.setCharacterEncoding("UTF-8");

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

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

System.out.println("id:"+ categoryId );

// 封装数据

Category cate = new Category(categoryId,categoryName);

// 处理数据

CategoryService src = new CategoryServiceImpl();

src.addCategory(categoryId, categoryName);

request.getSession().setAttribute("cateList",src.getCategoryDb());

// 显示结果

response.sendRedirect(request.getContextPath() + "/categoryList.jsp");

}

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

// TODO Auto-generated method stub

doGet(request, response);

}

}

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

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

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>新建图书分类</title>

<link rel="stylesheet" href="css/bootstrap.min.css">

<link rel="stylesheet" href="css/add.css">

</head>

<body>

<nav class="navbar navbar-default">

<div class="container">

<div class="navbar-header">

<a class="navbar-brand" href="">

图书分类管理

</a>

</div>

</div>

</nav>

<div class="container">

<div class="jumbotron">

<h1>Hello, XXX!</h1>

<p>请小心地新增图书分类，要是建了一个错误的就不好了。。。</p>

</div>

<div class="page-header">

<h3><small>新建</small></h3>

</div>

<form class="form-horizontal" action="${pageContext.request.contextPath }/AddCategoryServlet" method="post">

<div class="form-group">

<label for="name" class="col-sm-2 control-label">分类ID ：</label>

<div class="col-sm-8">

<input name="categoryId" class="form-control" id="categoryId">

</div>

</div>

<div class="form-group">

<label for="name" class="col-sm-2 control-label">分类名称：</label>

<div class="col-sm-8">

<input name="categoryName" class="form-control" id="categoryName">

</div>

</div>

<div class="form-group">

<div class="col-sm-offset-2 col-sm-10">

<button type="submit" class="btn btn-primary">保存</button>   

</div>

</div>

</form>

</div>

<footer class="text-center" >

copy@imooc

</footer>

</body>

</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

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

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>图书后台管理</title>

<link rel="stylesheet" href="css/index.css">

<link rel="stylesheet" href="css/bootstrap.min.css">

</head>

<body>

<header>

<div class="container">

<nav>

<a href="bookList.html" >图书信息管理</a>

</nav>

<nav>

<a href="${pageContext.request.contextPath }/categoryList.jsp" >分类管理</a>

</nav>

</div>

</header>

<section class="banner">

<div class="container">

<div>

<h1>图书管理系统</h1>

<p>图书分类管理</p>

</div>

</div>

</section>

<section class="main">

<div class="container">

<table class="table table-striped">

<thead>

<tr>

<th>序号</th>

<th>分类编号</th>

<th>分类名称</th>

<th>操作</th>

</tr>

</thead>

<tbody>

<c:forEach items="${sessionScope.cateList }" var ="ca" varStatus="idx">

<tr>

<td>${idx.index+1}</td>

<td>${ca.categoryId}</td>

<td>${ca.categoryName}</td>

<td><a href="/deleteCategory?categoryId=ca0001">删除</a></td>

</tr>

</c:forEach>

</tbody>

</table>

</div>

</section>

<section class="page">

<div class="container">

<div id="fatie">

<a href="addCategory.jsp"><button>新建</button></a>

</div>

</div>

</section>

<footer>

copy@慕课网

</footer>

</body>

</html>

传值一只是null。。

[Category [categoryId=null, categoryName=null], Category [categoryId=null, categoryName=null], Category [categoryId=null, categoryName=null]]

老师这是哪里出问题了，试好多种方法，找不到问题所在，就是一直无法传值进去

新增分类就只有序号，其他都是null

写回答

1回答

好帮手慕小班

好帮手慕小班

2020-07-03

已采纳

同学你好，检查同学贴出代码，在servlet中获取参数，调用addCategory方法的书写并没有问题，同学输出内容为空，是不是在Category 的构造方法的赋值有问题，同学可以将Category的内容贴出，老师来查看一下。

Ps: 在servlet中获取参数，比如 categoryName能正常获取到吗？

如果我的回答解决了你的疑惑，请采纳，祝学习愉快~

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