使用MyBatis

1、创建数据库、表

CREATE DATABASE mybatis;
USE mybatis;
CREATE TABLE `book` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(45) DEFAULT NULL,
  `author` varchar(45) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

2、新建SpringBoot项目

• 使用Spring Initializer：

• 填写项目相关信息：

• 添加部分依赖：

• 项目保存路径等信息：

• 项目结构：

• 自动导入依赖：

• 手动添加druid数据源（pom.xml）：

  <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.1.21</version>
  </dependency>

  3、MyBatis基础配置

• 数据库连接信息（application.yaml）：

  spring:
    datasource:
      type: com.alibaba.druid.pool.DruidDataSource
      url: jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
      username: root
      password: root

• MyBatis基本配置：

  • 开启实体类与数据库名字按驼峰式相互匹配。
  • 配置Mapper.xml文件所在的目录。

    mybatis:
    configuration:
      map-underscore-to-camel-case: true
    mapper-locations: classpath:/mapper/*.xml

• 在启动类中，配置MapperScan，扫描该包下的所有接口作为DAO：

  package com.xianhuii;
  
  import org.mybatis.spring.annotation.MapperScan;
  import org.springframework.boot.SpringApplication;
  import org.springframework.boot.autoconfigure.SpringBootApplication;
  
  @MapperScan("com.xianhuii.mapper")
  @SpringBootApplication
  public class SpringbootMybatisApplication {
  
      public static void main(String[] args) {
          SpringApplication.run(SpringbootMybatisApplication.class, args);
      }
  }

  4、实体类

    package com.xianhuii.entity;
  
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
  
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class Book {
        private Integer id;
        private String name;
        private String author;
    }

  5、DAO

• Mapper接口：

  package com.xianhuii.mapper;
  
  import com.xianhuii.entity.Book;
  
  import java.util.List;
  
  public interface BookMapper {
      Integer addBook(Book book);
  
      Integer deleteBookById(Integer id);
  
      Integer updateBookById(Book book);
  
      Book getBookById(Integer id);
  
      List<Book> getAllBooks();
  }

• Mapper配置文件：

  <?xml version="1.0" encoding="UTF-8" ?>
  
  <!DOCTYPE mapper
          PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
          "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
  <mapper namespace="com.xianhuii.mapper.BookMapper">
  
      <!--Integer addBook(Book book)-->
      <insert id="addBook" parameterType="com.xianhuii.entity.Book">
          insert into book (name, author) values (#{name}, #{author})
      </insert>
  
      <!--Integer deleteBookById(Integer id)-->
      <delete id="deleteBookById" parameterType="int">
          delete from book where id = #{id}
      </delete>
  
      <!--Integer updateBookById(Book book)-->
      <update id="updateBookById" parameterType="com.xianhuii.entity.Book">
          update book set name = #{name}, author = #{author} where id = #{id}
      </update>
  
      <!--Book getBookById(Integer id)-->
      <select id="getBookById" parameterType="int" resultType="com.xianhuii.entity.Book">
          select * from book where id = #{id}
      </select>
  
      <!--List<Book> getAllBooks()-->
      <select id="getAllBooks" resultType="com.xianhuii.entity.Book">
          select * from book
      </select>
  </mapper>

  6、测试

    package com.xianhuii.mapper;
  
    import com.xianhuii.SpringbootMybatisApplication;
    import com.xianhuii.entity.Book;
    import org.junit.jupiter.api.Test;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
  
    import javax.annotation.security.RunAs;
  
    import java.util.Iterator;
    import java.util.List;
  
    import static org.junit.jupiter.api.Assertions.*;
    // 不加这个注解会报：java.lang.NullPointerException
    @SpringBootTest(classes = SpringbootMybatisApplication.class)
    class BookMapperTest {
        @Autowired
        private BookMapper bookMapper;
  
        @Test
        void addBook() {
            Book book1 = new Book(null, "三国演义", "罗贯中");
            Book book2 = new Book(null, "水浒传", "施耐庵");
            Book book3 = new Book(null, "西游记", "吴承恩");
            Book book4 = new Book(null, "红楼梦", "曹雪芹");
            bookMapper.addBook(book1);
            bookMapper.addBook(book2);
            bookMapper.addBook(book3);
            bookMapper.addBook(book4);
        }
  
        @Test
        void deleteBookById() {
            System.out.println(bookMapper.deleteBookById(1));
        }
  
        @Test
        void updateBookById() {
            Book book = new Book(2, "水浒传2", "施耐庵2");
            System.out.println(bookMapper.updateBookById(book));
        }
  
        @Test
        void getBookById() {
            Book book = bookMapper.getBookById(1);
            System.out.println(book.getId() + "-" + book.getName() + "-" + book.getAuthor());
        }
  
        @Test
        void getAllBooks() {
            List<Book> books = bookMapper.getAllBooks();
            Iterator<Book> iterator = books.iterator();
            while (iterator.hasNext()) {
                Book book = iterator.next();
                System.out.println(book.getId() + "-" + book.getName() + "-" + book.getAuthor());
            }
        }
    }

  7、项目结构