笔记66 Spring Boot快速入门（六）

SpringBoot中使用Mybatis

一、注解方式

1.创建映射文件CategoryMapper.java

使用注解@Mapper 表示这是一个Mybatis Mapper接口。
使用@Select注解表示调用findAll方法会去执行对应的sql语句。

 package com.example.springbootmybatisdemo.mapper;

 import com.example.springbootmybatisdemo.pojo.Category;
 import org.apache.ibatis.annotations.Mapper;
 import org.apache.ibatis.annotations.Select;

 import java.util.List;

 @Mapper
 public interface CategoryMapper {
     @Select("select * from category")
     List<Category> findAll();
 }

2.创建CategoryController.java

有问题：无法自动加载mapper，显示有错误，但是运行结果正确。

 package com.example.springbootmybatisdemo.controller;

 import com.example.springbootmybatisdemo.mapper.CategoryMapper;
 import com.example.springbootmybatisdemo.pojo.Category;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
 import org.springframework.web.bind.annotation.RequestMapping;

 import java.util.List;

 @Controller
 public class CategoryController {
     @Autowired
     private CategoryMapper categoryMapper;

     @RequestMapping("/listCategory")
     public String listCategory(Model model) throws Exception{
         List<Category> categories=categoryMapper.findAll();
         model.addAttribute("category",categories);
         System.out.println();
         return "listCategory";
     }
 }

3.listCategory.html

 <!DOCTYPE html>
 <html lang="en" xmlns:th="http://www.thymeleaf.org">
 <head>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
     <title>Title</title>
 </head>
 <body>
 <div class="showing">
     <h2>SpringBoot+mybatis</h2>

     <table>
         <thead>
         <tr>
             <th>id</th>
             <th>name</th>
         </tr>
         </thead>
         <tbody>
         <tr th:each="c: ${category}">
             <td align="center" th:text="${c.id}"></td>
             <td align="center" th:text="${c.name}"></td>
         </tr>
         </tbody>
     </table>
 </div>
 </body>
 </html>

二、xml方式(有问题)

三、SpringBoot+Mybatis抽插数据库

1.使用第三方插件PageHelper进行分页查询

增加依赖：

         <dependency>
             <groupId>com.github.pagehelper</groupId>
             <artifactId>pagehelper</artifactId>
             <version>4.1.6</version>
         </dependency>

2.配置PageHelper

　　PageHelperConfig.java

 package com.example.springbootmybatisdemo.config;

 import com.github.pagehelper.PageHelper;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;

 import java.util.Properties;

 @Configuration
 public class PageHelperConfig {
     @Bean
     public PageHelper pageHelper(){
         PageHelper pageHelper = new PageHelper();
         Properties p = new Properties();
         p.setProperty("offsetAsPageNum", "true");
         p.setProperty("rowBoundsWithCount", "true");
         p.setProperty("reasonable", "true");
         pageHelper.setProperties(p);
         return pageHelper;
     }
 }

注解@Configuration 表示PageHelperConfig 这个类是用来做配置的。
注解@Bean 表示启动PageHelper这个拦截器。

offsetAsPageNum:设置为true时，会将RowBounds第一个参数offset当成pageNum页码使用.

p.setProperty("offsetAsPageNum", "true");

rowBoundsWithCount:设置为true时，使用RowBounds分页会进行count查询.

p.setProperty("rowBoundsWithCount", "true");

reasonable：启用合理化时，如果pageNum<1会查询第一页，如果pageNum>pages会查询最后一页。比jpa中Pageable进行分页查询时更合理，不需要再去处理。

p.setProperty("reasonable", "true");

3.修改映射mapper

CategoryMapper.java

 package com.example.springbootmybatisdemo.mapper;

 import com.example.springbootmybatisdemo.pojo.Category;
 import org.apache.ibatis.annotations.*;

 import java.util.List;

 @Mapper
 public interface CategoryMapper {
     @Select("select * from category")
     List<Category> findAll();

     @Insert("insert into category(name) values (#{name})")
     int save(Category category);

     @Delete(" delete from category where id= #{id} ")
      void delete(int id);

     @Select("select * from category where id= #{id} ")
     Category get(int id);

     @Update("update category set name=#{name} where id=#{id} ")
     int update(Category category);
 }

4.控制层

CategoryController.java

 package com.example.springbootmybatisdemo.controller;

 import com.example.springbootmybatisdemo.mapper.CategoryMapper;
 import com.example.springbootmybatisdemo.pojo.Category;
 import com.github.pagehelper.PageHelper;
 import com.github.pagehelper.PageInfo;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestParam;

 import java.util.List;

 @Controller
 public class CategoryController {
     @Autowired
     private CategoryMapper categoryMapper;

     @RequestMapping("/listCategory")
     public String listCategory(Model model) throws Exception{
         List<Category> categories=categoryMapper.findAll();
         model.addAttribute("category",categories);
         System.out.println();
         return "listCategory";
     }

     @RequestMapping("/listCategories")
     public String listCategories(Model model,
                                  @RequestParam(value = "start",defaultValue = "0")int start,
                                  @RequestParam(value = "size",defaultValue = "5") int size) throws Exception{
         PageHelper.startPage(start,size,"id desc");
         List<Category> categories=categoryMapper.findAll();
         PageInfo<Category> pageInfo=new PageInfo<>(categories);
         System.out.println(pageInfo.getPageNum());
         model.addAttribute("pageInfo",pageInfo);
         return "listCategories";
     }

     @RequestMapping("/addCategory")
     public String addCategory(Category category) throws Exception{
         categoryMapper.save(category);
         return "redirect:listCategories";
     }
     @RequestMapping("/deleteCategory")
     public String deleteCategory(Category category)throws Exception{
         categoryMapper.delete(category.getId());
         return "redirect:listCategories";
     }
     @RequestMapping("/updateCategory")
     public String updateCategory(Category category)throws Exception{
         categoryMapper.update(category);
         return "redirect:listCategories";
     }
     @RequestMapping("/editCategory")
     public String editCategory(int id,Model model)throws Exception{
         Category category=categoryMapper.get(id);
         model.addAttribute("category",category);
         return "editCategory";
     }

 } 

根据start,size进行分页，并且设置id 倒排序

　　PageHelper.startPage(start,size,"id desc");

因为PageHelper的作用，这里就会返回当前分页的集合了

　　List<Category> categories=categoryMapper.findAll();

根据返回的集合，创建PageInfo对象

　　PageInfo<Category> page = new PageInfo<>(categories);

5.视图层

listCategories.html

 <!DOCTYPE html>
 <html lang="en" xmlns:th="http://www.thymeleaf.org">
 <head>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
     <title>Title</title>
 </head>
 <body>
 <div class="showing">
     <h2>SpringBoot+Mybatis</h2>
     <div style="width:500px;margin:20px auto;text-align: center">
         <table align="center" border="1" cellspacing="0">
             <thead>
             <tr>
                 <th>id</th>
                 <th>name</th>
                 <td>编辑</td>
                 <td>删除</td>
             </tr>
             </thead>
             <tbody>
             <tr th:each="c: ${pageInfo.list}">
                 <td align="center" th:text="${c.id}"></td>
                 <td align="center" th:text="${c.name}"></td>
                 <td align="center" ><a th:href="@{/editCategory(id=${c.id})}">编辑</a></td>
                 <td align="center" ><a th:href="@{/deleteCategory(id=${c.id})}">删除</a></td>
             </tr>
             </tbody>
         </table>
         <br />
         <div>
             <a th:href="@{/listCategories(start=1)}">[首  页]</a>
             <a th:href="@{/listCategories(start=${pageInfo.pageNum -1})}">[上一页]</a>
             <a th:href="@{/listCategories(start=${pageInfo.pageNum +1})}">[下一页]</a>
             <a th:href="@{/listCategories(start=${pageInfo.pages})}">[末  页]</a>
         </div>
         <form action="/addCategory" method="post">
             name:<input name="name"/><br/>
             <button type="submit">提交</button>
         </form>
     </div>
 </div>
 </body>
 </html>

editCategory.html

 <!DOCTYPE html>
 <html lang="en" xmlns:th="http://www.thymeleaf.org">
 <head>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
     <title>Title</title>
 </head>
 <body>
 <div class="showing">
     <h2>springboot+jpa</h2>

     <div style="margin:0px auto; width:500px">

         <form action="/updateCategory" method="post">

             name: <input name="name" th:value="${category.name}" /> <br/>

             <input name="id" type="hidden" th:value="${category.id}" />
             <button type="submit">提交</button>

         </form>
     </div>
 </div>
 </body>
 </html>

5.测试

6.问题：当编辑完以后就返回首页了。

修改：在编辑时传入当前分页数，然后跳转到listCategories的时候传入start。

四、代码

https://github.com/lyj8330328/springboot-mybatis-demo