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。

 1 package com.example.springbootmybatisdemo.mapper;
 2 
 3 import com.example.springbootmybatisdemo.pojo.Category;
 4 import org.apache.ibatis.annotations.Mapper;
 5 import org.apache.ibatis.annotations.Select;
 6 
 7 import java.util.List;
 8 
 9 
10 @Mapper
11 public interface CategoryMapper {
12     @Select("select * from category")
13     List<Category> findAll();
14 }

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。

 1 package com.example.springbootmybatisdemo.controller;
 2 
 3 import com.example.springbootmybatisdemo.mapper.CategoryMapper;
 4 import com.example.springbootmybatisdemo.pojo.Category;
 5 import org.springframework.beans.factory.annotation.Autowired;
 6 import org.springframework.stereotype.Controller;
 7 import org.springframework.ui.Model;
 8 import org.springframework.web.bind.annotation.RequestMapping;
 9 
10 import java.util.List;
11 
12 @Controller
13 public class CategoryController {
14     @Autowired
15     private CategoryMapper categoryMapper;
16 
17     @RequestMapping("/listCategory")
18     public String listCategory(Model model) throws Exception{
19         List<Category> categories=categoryMapper.findAll();
20         model.addAttribute("category",categories);
21         System.out.println();
22         return "listCategory";
23     }
24 }

3.listCategory.html

 1 <!DOCTYPE html>
 2 <html lang="en" xmlns:th="http://www.thymeleaf.org">
 3 <head>
 4     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
 5     <title>Title</title>
 6 </head>
 7 <body>
 8 <div class="showing">
 9     <h2>SpringBoot+mybatis</h2>
10 
11     <table>
12         <thead>
13         <tr>
14             <th>id</th>
15             <th>name</th>
16         </tr>
17         </thead>
18         <tbody>
19         <tr th:each="c: ${category}">
20             <td align="center" th:text="${c.id}"></td>
21             <td align="center" th:text="${c.name}"></td>
22         </tr>
23         </tbody>
24     </table>
25 </div>
26 </body>
27 </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：

1         <dependency>
2             <groupId>com.github.pagehelper</groupId>
3             <artifactId>pagehelper</artifactId>
4             <version>4.1.6</version>
5         </dependency>

2.配置PageHelper

　　PageHelperConfig.java

 1 package com.example.springbootmybatisdemo.config;
 2 
 3 import com.github.pagehelper.PageHelper;
 4 import org.springframework.context.annotation.Bean;
 5 import org.springframework.context.annotation.Configuration;
 6 
 7 import java.util.Properties;
 8 
 9 @Configuration
10 public class PageHelperConfig {
11     @Bean
12     public PageHelper pageHelper(){
13         PageHelper pageHelper = new PageHelper();
14         Properties p = new Properties();
15         p.setProperty("offsetAsPageNum", "true");
16         p.setProperty("rowBoundsWithCount", "true");
17         p.setProperty("reasonable", "true");
18         pageHelper.setProperties(p);
19         return pageHelper;
20     }
21 }

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

 1 package com.example.springbootmybatisdemo.mapper;
 2 
 3 import com.example.springbootmybatisdemo.pojo.Category;
 4 import org.apache.ibatis.annotations.*;
 5 
 6 import java.util.List;
 7 
 8 
 9 @Mapper
10 public interface CategoryMapper {
11     @Select("select * from category")
12     List<Category> findAll();
13 
14     @Insert("insert into category(name) values (#{name})")
15     int save(Category category);
16 
17     @Delete(" delete from category where id= #{id} ")
18      void delete(int id);
19 
20     @Select("select * from category where id= #{id} ")
21     Category get(int id);
22 
23     @Update("update category set name=#{name} where id=#{id} ")
24     int update(Category category);
25 }

4.控制层

CategoryController.java

 1 package com.example.springbootmybatisdemo.controller;
 2 
 3 import com.example.springbootmybatisdemo.mapper.CategoryMapper;
 4 import com.example.springbootmybatisdemo.pojo.Category;
 5 import com.github.pagehelper.PageHelper;
 6 import com.github.pagehelper.PageInfo;
 7 import org.springframework.beans.factory.annotation.Autowired;
 8 import org.springframework.stereotype.Controller;
 9 import org.springframework.ui.Model;
10 import org.springframework.web.bind.annotation.RequestMapping;
11 import org.springframework.web.bind.annotation.RequestParam;
12 
13 import java.util.List;
14 
15 @Controller
16 public class CategoryController {
17     @Autowired
18     private CategoryMapper categoryMapper;
19 
20     @RequestMapping("/listCategory")
21     public String listCategory(Model model) throws Exception{
22         List<Category> categories=categoryMapper.findAll();
23         model.addAttribute("category",categories);
24         System.out.println();
25         return "listCategory";
26     }
27 
28     @RequestMapping("/listCategories")
29     public String listCategories(Model model,
30                                  @RequestParam(value = "start",defaultValue = "0")int start,
31                                  @RequestParam(value = "size",defaultValue = "5") int size) throws Exception{
32         PageHelper.startPage(start,size,"id desc");
33         List<Category> categories=categoryMapper.findAll();
34         PageInfo<Category> pageInfo=new PageInfo<>(categories);
35         System.out.println(pageInfo.getPageNum());
36         model.addAttribute("pageInfo",pageInfo);
37         return "listCategories";
38     }
39 
40     @RequestMapping("/addCategory")
41     public String addCategory(Category category) throws Exception{
42         categoryMapper.save(category);
43         return "redirect:listCategories";
44     }
45     @RequestMapping("/deleteCategory")
46     public String deleteCategory(Category category)throws Exception{
47         categoryMapper.delete(category.getId());
48         return "redirect:listCategories";
49     }
50     @RequestMapping("/updateCategory")
51     public String updateCategory(Category category)throws Exception{
52         categoryMapper.update(category);
53         return "redirect:listCategories";
54     }
55     @RequestMapping("/editCategory")
56     public String editCategory(int id,Model model)throws Exception{
57         Category category=categoryMapper.get(id);
58         model.addAttribute("category",category);
59         return "editCategory";
60     }
61 
62 
63 }

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

 1 <!DOCTYPE html>
 2 <html lang="en" xmlns:th="http://www.thymeleaf.org">
 3 <head>
 4     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
 5     <title>Title</title>
 6 </head>
 7 <body>
 8 <div class="showing">
 9     <h2>SpringBoot+Mybatis</h2>
10     <div style="500px;margin:20px auto;text-align: center">
11         <table align="center" border="1" cellspacing="0">
12             <thead>
13             <tr>
14                 <th>id</th>
15                 <th>name</th>
16                 <td>编辑</td>
17                 <td>删除</td>
18             </tr>
19             </thead>
20             <tbody>
21             <tr th:each="c: ${pageInfo.list}">
22                 <td align="center" th:text="${c.id}"></td>
23                 <td align="center" th:text="${c.name}"></td>
24                 <td align="center" ><a th:href="@{/editCategory(id=${c.id})}">编辑</a></td>
25                 <td align="center" ><a th:href="@{/deleteCategory(id=${c.id})}">删除</a></td>
26             </tr>
27             </tbody>
28         </table>
29         <br />
30         <div>
31             <a th:href="@{/listCategories(start=1)}">[首  页]</a>
32             <a th:href="@{/listCategories(start=${pageInfo.pageNum -1})}">[上一页]</a>
33             <a th:href="@{/listCategories(start=${pageInfo.pageNum +1})}">[下一页]</a>
34             <a th:href="@{/listCategories(start=${pageInfo.pages})}">[末  页]</a>
35         </div>
36         <form action="/addCategory" method="post">
37             name:<input name="name"/><br/>
38             <button type="submit">提交</button>
39         </form>
40     </div>
41 </div>
42 </body>
43 </html>

editCategory.html

 1 <!DOCTYPE html>
 2 <html lang="en" xmlns:th="http://www.thymeleaf.org">
 3 <head>
 4     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
 5     <title>Title</title>
 6 </head>
 7 <body>
 8 <div class="showing">
 9     <h2>springboot+jpa</h2>
10 
11     <div style="margin:0px auto; 500px">
12 
13         <form action="/updateCategory" method="post">
14 
15             name: <input name="name" th:value="${category.name}" /> <br/>
16 
17             <input name="id" type="hidden" th:value="${category.id}" />
18             <button type="submit">提交</button>
19 
20         </form>
21     </div>
22 </div>
23 </body>
24 </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