Springboot使用Mybatis实现完整的增删改查（CRUD）和分页

Mybatis CRUD和分页

这里使用 Mybatis 来做一个完整的CRUD和分页。其中分页使用 Mybatis 里的 PageHelper 插件。
相关：mybatis PageHelper 教程

步骤 1 : 可运行项目

首先下载一个简单的可运行项目作为演示：网盘链接：https://www.90pan.com/b1869095

下载后解压，比如解压到 E:projectspringboot 目录下

步骤 2 : pom.xml

增加对 PageHelper 的支持

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

完整 pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

  <groupId>com.ryan</groupId>
  <artifactId>springboot</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>springboot</name>
  <description>springboot</description>
  <packaging>war</packaging>
  
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            
        </dependency>
	    <dependency>
		      <groupId>junit</groupId>
		      <artifactId>junit</artifactId>
		      <version>3.8.1</version>
		      <scope>test</scope>
	    </dependency>
  		<!-- servlet依赖. -->
        <dependency>
              <groupId>javax.servlet</groupId>
              <artifactId>javax.servlet-api</artifactId>
              
        </dependency>
              <dependency>
                     <groupId>javax.servlet</groupId>
                     <artifactId>jstl</artifactId>
              </dependency>
        <!-- tomcat的支持.-->
        <dependency>
               <groupId>org.apache.tomcat.embed</groupId>
               <artifactId>tomcat-embed-jasper</artifactId>               
        </dependency>	    
		<dependency>
		    <groupId>org.springframework.boot</groupId>
		    <artifactId>spring-boot-devtools</artifactId>
		    <optional>true</optional> <!-- 这个需要为 true 热部署才有效 -->
		</dependency>
        
		<!-- mybatis -->
                <dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>1.1.1</version>
		</dependency>

		<!-- mysql -->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.21</version>
		</dependency>
		
		<!-- 分页插件 -->
		<dependency>
			<groupId>com.github.pagehelper</groupId>
			<artifactId>pagehelper</artifactId>
			<version>4.1.6</version>
		</dependency>
		
    </dependencies>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

步骤 3 : PageHelperConfig

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。

新增加一个包 com.ryan.springboot.config，然后添加一个类 PageHelperConfig ，其中进行 PageHelper 相关配置。

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

注：RowBounds是什么鬼？我也没搞太清楚。。。反正这么复制粘贴就对了：|

package com.ryan.springboot.config;
 
import java.util.Properties;
 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
import com.github.pagehelper.PageHelper;
 
@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;
    }
}

步骤 4 : CategoryMapper

修改 CategoryMapper，增加 CRUD 方法的支持。其实就是调用不同的SQL语句。

package com.ryan.springboot.mapper;

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.ryan.springboot.pojo.Category;

@Mapper
public interface CategoryMapper {

    @Select("select * from category_ ")
    List<Category> findAll();

    @Insert(" insert into category_ ( name ) values (#{name}) ")
    public int save(Category category); 
     
    @Delete(" delete from category_ where id= #{id} ")
    public void delete(int id);
         
    @Select("select * from category_ where id= #{id} ")
    public Category get(int id);
       
    @Update("update category_ set name=#{name} where id=#{id} ")
    public int update(Category category);  

}

步骤 5 : CategoryController

为 CategoryController 添加：增加、删除、获取、修改映射

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

修改查询映射

@RequestMapping("/listCategory")
public String listCategory(Model m,@RequestParam(value = "start", defaultValue = "0") int start,@RequestParam(value = "size", defaultValue = "6") int size) throws Exception {
    PageHelper.startPage(start,size,"id desc");
    List<Category> cs=categoryMapper.findAll();
    PageInfo<Category> page = new PageInfo<>(cs);
    m.addAttribute("page", page);        
    return "listCategory";
}

在参数里接受当前是第几页 start ，以及每页显示多少条数据 size。默认值分别是0和6。
@RequestParam(value = "start", defaultValue = "0") int start,@RequestParam(value = "size", defaultValue = "6"
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> cs = categoryMapper.findAll();
根据返回的集合，创建 PageInfo 对象
PageInfo<Category> page = new PageInfo<>(cs);
把 PageInfo 对象扔进 model，以供后续显示
m.addAttribute("page", page);
跳转到 listCategory.jsp
return "listCategory";

完整 CategoryController 类：

package com.ryan.springboot.web;
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.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.ryan.springboot.mapper.CategoryMapper;
import com.ryan.springboot.pojo.Category;
   
@Controller
public class CategoryController {
    @Autowired CategoryMapper categoryMapper;
      
    @RequestMapping("/addCategory")
    public String listCategory(Category c) throws Exception {
        categoryMapper.save(c);
        return "redirect:listCategory";
    }
    @RequestMapping("/deleteCategory")
    public String deleteCategory(Category c) throws Exception {
        categoryMapper.delete(c.getId());
        return "redirect:listCategory";
    }
    @RequestMapping("/updateCategory")
    public String updateCategory(Category c) throws Exception {
        categoryMapper.update(c);
        return "redirect:listCategory";
    }
    @RequestMapping("/editCategory")
    public String listCategory(int id,Model m) throws Exception {
        Category c= categoryMapper.get(id);
        m.addAttribute("c", c);
        return "editCategory";
    }
     
    @RequestMapping("/listCategory")
    public String listCategory(Model m,@RequestParam(value = "start", defaultValue = "0") int start,@RequestParam(value = "size", defaultValue = "6") int size) throws Exception {
        PageHelper.startPage(start,size,"id desc");
        List<Category> cs=categoryMapper.findAll();
        PageInfo<Category> page = new PageInfo<>(cs);
        m.addAttribute("page", page);        
        return "listCategory";
    }
     
}

步骤 6 : listCategory.jsp

通过 page.getList 遍历当前页面的 Category 对象。
在分页的时候通过 page.pageNum 获取当前页面，page.pages 获取总页面数。

注：page.getList会返回一个泛型是 Category 的集合。

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
  
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
    
<div align="center">
  
</div>
  
<div style="500px;margin:20px auto;text-align: center">
    <table align='center' border='1' cellspacing='0'>
        <tr>
            <td>id</td>
            <td>name</td>
            <td>编辑</td>
            <td>删除</td>
        </tr>
        <c:forEach items="${page.list}" var="c" varStatus="st">
            <tr>
                <td>${c.id}</td>
                <td>${c.name}</td>
                <td><a href="editCategory?id=${c.id}">编辑</a></td>
                <td><a href="deleteCategory?id=${c.id}">删除</a></td>
            </tr>
        </c:forEach>
          
    </table>
    <br>
    <div>
                <a href="?start=1">[首  页]</a>
            <a href="?start=${page.pageNum-1}">[上一页]</a>
            <a href="?start=${page.pageNum+1}">[下一页]</a>
            <a href="?start=${page.pages}">[末  页]</a>
    </div>
    <br>
    <form action="addCategory" method="post">
      
    name: <input name="name"> <br>
    <button type="submit">提交</button>
      
    </form>
</div>

步骤 7 : editCategory.jsp

修改分类的页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8" isELIgnored="false"%>
  
<div style="margin:0px auto; 500px">
  
<form action="updateCategory" method="post">
  
name: <input name="name" value="${c.name}"> <br>
  
<input name="id" type="hidden" value="${c.id}">
<button type="submit">提交</button>
  
</form>
</div>

步骤 8 : 重启测试访问

因为在pom中增加了新jar的依赖，所以要手动重启，重启后访问测试地址：

http://127.0.0.1:8080/listCategory?start=1

注：启动方式是 Springboot 特有的，直接运行类：com.ryan.springboot.Application 的主方法。

更多关于 Springboot mybatis 详细内容，点击学习： http://t.cn/A62lrLjb