写在前面：2020年面试必备的Java后端进阶面试题总结了一份复习指南在Github上，内容详细，图文并茂，有需要学习的朋友可以Star一下！
GitHub地址：https://github.com/abel-max/Java-Study-Note/tree/master
将数据库商品数据进行-增.删.改.查
一、创建项目并添加依赖
*创建项目并设置基本信息
*指定项目核心依赖
Spring Boot小结——增.删.改.查了解一下
*项目结构
Spring Boot小结——增.删.改.查了解一下
*项目配置文件
Spring Boot小结——增.删.改.查了解一下
二、业务实现
*Pojo类定义
*Dao接口方法及映射定义
package com.cy.pj.goods.dao;
import java.util.List;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import com.cy.pj.goods.pojo.Goods;
@Mapperpublic interface GoodsDao { //查询
@Select("select * from tb_goods")
List<Goods> findGoods(); //删除
@Delete("delete from tb_goods where id=#{id}")
int deleteById(Integer id); //添加
@Insert("insert into tb_goods(name,remark,createdTime) value(#{name},#{remark},now())")
int insertObject(Goods entity); //修改
@Select("select * from tb_goods where id=#{id}")
Goods findById(Integer id); @Update("update tb_goods set name=#{name},remark=#{remark} where id=#{id} ")
int updateGoods(Goods goods);}
*Service接口方法定义及实现
package com.cy.pj.goods.service;
import java.util.List;
import com.cy.pj.goods.pojo.Goods;
public interface GoodsService {
//查询
List<Goods> findGoods();
//删除
int deleteById(Integer id);
//添加
int saveGoods(Goods entity);
//修改
Goods findById(Integer id);
int updateGoods(Goods goods);
}
*定义接口实现类GoodsServiceImpl及方法实现
package com.cy.pj.goods.service.impl;
import java.util.List;importorg.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import com.cy.pj.goods.dao.GoodsDao;import com.cy.pj.goods.pojo.Goods;import com.cy.pj.goods.service.GoodsService;@Servicepublic class GoodsServiceImpl implements GoodsService { @Autowired private GoodsDao goodsDao; @Override //查询 public List<Goods> findGoods() { return goodsDao.findGoods();
} @Override //删除 public int deleteById(Integer id) {
int rows = goodsDao.deleteById(id);
return rows;
} @Override //添加 public int saveGoods(Goods entity) {
int rows = goodsDao.insertObject(entity);
return rows;
} @Override //修改 public Goods findById(Integer id) { return goodsDao.findById(id);
} @Override public int updateGoods(Goods goods) {
return goodsDao.updateGoods(goods);
} }
*Controller对象方法定义及实现
package com.cy.pj.goods.controller;
import java.util.List;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import com.cy.pj.goods.pojo.Goods;import com.cy.pj.goods.service.GoodsService;@Controller@RequestMapping("/goods/")
public class GoodsController { @Autowired private GoodsService goodsService; @RequestMapping("doGoodsUI") //查詢
public String doGoodsUI(Model model) { List<Goods> list = goodsService.findGoods(); model.addAttribute("list", list);
return "goods";
} @RequestMapping("doDeleteById/{id}") //刪除
public String doDeleteById(@PathVariable Integer id) { goodsService.deleteById(id); return "redirect:/goods/doGoodsUI";
} @RequestMapping("doSaveGoods") //添加
public String doSaveGoods(Goods entity) { goodsService.saveGoods(entity); return "redirect:/goods/doGoodsUI";
} @RequestMapping("doGoodsAddUI")
public String doGoodsAddUI() { return "goods-add";
} @RequestMapping("doUpdateGoods") //修改
public String doUpdateGoods(Goods goods) { goodsService.updateGoods(goods); return "redirect:/goods/doGoodsUI";
} @RequestMapping("doFindById/{id}")
public String doFindById(@PathVariable Integer id, Model model) { Goods goods = goodsService.findById(id); model.addAttribute("goods", goods);
return "goods-update";
}}
*设计Goods列表页面及实现
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>The Goods Page</h1>
<table width="50%">
<a th:href="@{/goods/doGoodsAddUI}">添加商品</a>
<thead>
<th>id</th>
<th>name</th>
<th>remark</th>
<th>createdTime</th>
<th colspan="2">operation</th>
</thead>
<tbody>
<tr th:each="g:${list}">
<td th:text="${g.id}">1</td>
<td th:text="${g.name}">fbb</td>
<td th:text="${g.remark}">fbbbb</td>
<td th:text="${#dates.format(g.createdTime,'yyyy/MM/dd HH:mm')}">2020/09/01</td>
<td><a th:href="@{/goods/doDeleteById/{id}(id=${g.id})}">delete</a></td>
<td><a th:href="@{/goods/doFindById/{id}(id=${g.id})}">update</a></td>
</tr>
</tbody>
</table>
</body>
</html>
*增--创建goods-add.html页面
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style type="text/css">
ul li {list-style-type:none}
</style>
</head>
<body>
<h1>The Goods Add Page</h1>
<form th:action="@{/goods/doSaveGoods}" method="post">
<ul>
<li>name:
<li><input type="text" name="name">
<li>remark:
<li><textarea rows="5" cols="50" name="remark"></textarea>
<li><input type="submit" value="Save">
</ul>
</form>
</body>
</html>
*改--创建goods-update.html页面
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style type="text/css">
ul li {list-style-type:none}
</style>
</head>
<body>
<h1>The Goods Update Page</h1>
<form th:action="@{/goods/doUpdateGoods}" method="post">
<input type="hidden" name="id" th:value="${goods.id}">
<ul>
<li>name:
<li><input type="text" name="name" th:value="${goods.name}">
<li>remark:
<li><textarea rows="3" cols="30" name="remark" th:text="${goods.remark}"></textarea>
<li><input type="submit" value="Update Goods">
</ul>
</form>
</body>
</html>
三、易错分析
- 404--服务器依据请求资源路径找不到对应的资源。1)错误原因:
a,请求地址写错了
b,<servlet-name>不一致
2)解决方式:
a,依据 http://ip :port/appname/servlet-url检查请求地址。
b,检查/.xml文件。
- 500--运行时出错。
1)错误原因:
a,配置文件类名写错了。
b,程序代码写错。
2)解决方式:
a,检查/.xml文件。有没有把类名写错（必须是完整类名）
b,检查程序代码。
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