MyBatis的增删改查SpringBoot方式

使用IDEA建立一个SpringBoot项目。

1、POM文件：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.6</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>MyBatisBoot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>MyBatisBoot</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

2、建立实体类SysUser：

package com.yas.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

import java.util.Date;

@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class SysUser {
    private Integer id;
    private String account;
    private String username;
    private String pwd;
    private Date gmt_create;
    private Date gmt_modified;
}

3、增删改查的UserDAO，(使用注解方式)：

package com.yas.dao;

import com.yas.entity.SysUser;
import org.apache.ibatis.annotations.*;

import java.util.List;
import java.util.Map;

@Mapper
public interface UserDAO {
    @Select("SELECT * FROM sys_user WHERE id = #{id}")
    SysUser queryUserById(Integer id);

    //使用@Param注解，标注参数
    @Select("SELECT * FROM sys_user WHERE id = #{id} and username = #{username}")
    SysUser queryUserByIdAndUsername(@Param("id") Integer id,@Param("username") String username);

    //使用Map封装参数
    @Select("SELECT * FROM sys_user WHERE id = #{id} and username = #{username}")
    SysUser queryUserByMap(Map map);

    @Select("SELECT * FROM sys_user WHERE id = #{id} and username = #{username}")
    SysUser queryUserByEntity(SysUser user);

    @Select("SELECT * FROM sys_user WHERE username like concat('%',#{username},'%')")
    List<SysUser> queryUserByUsername(@Param("username") String username);

    @Delete("DELETE FROM sys_user WHERE id = #{id}")
    Integer deleteUser(@Param("id") Integer id);

    @Update("UPDATE sys_user SET username = #{username} WHERE id = #{id}")
    Integer updateUser(SysUser user);

    @Insert("INSERT INTO sys_user VALUES(#{id},#{account},#{username},#{pwd},#{gmt_create},#{gmt_modified})")
    @Options(useGeneratedKeys = true,keyProperty = "id")
    Integer insertUser(SysUser user);
}

4、在resources目录下的，application.properties文件中添加配置信息：

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/lending_management?characterEncoding=utf-8
spring.datasource.username=root
spring.datasource.password=root

#开启mybatis的数据库日志
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl 

5、测试类：

package com.yas;

import com.yas.dao.UserDAO;
import com.yas.entity.SysUser;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.*;

@SpringBootTest
class MyBatisBootApplicationTests {
    @Autowired
    UserDAO userDAO;

    @Test
    void queryUserById() {
//        SysUser user1 = userDAO.queryUserById(1);
//        System.out.println(user1);

//        SysUser user2 = userDAO.queryUserByIdAndUsername(2,"刘翔");
//        System.out.println(user2);

//        Map<String,String> map = new HashMap<>();
//        map.put("id","1");
//        map.put("username","管理员");
//        SysUser user3 = userDAO.queryUserByMap(map);
//        System.out.println(user3);

//        SysUser user = new SysUser();
//        user.setId(1);
//        user.setUsername("管理员");
//        SysUser user4 = userDAO.queryUserByEntity(user);
//        System.out.println(user4);

//        List<SysUser> users = userDAO.queryUserByUsername("C");
//        for (SysUser user : users) {
//            System.out.println(user);
//        }

//        userDAO.deleteUser(83);

        SysUser user = new SysUser(5,"manager","李白","000000",new Date(),new Date());
        userDAO.insertUser(user);
    }
}

补充，如果使用注解与xml配置文件混合开发的方式，可以在配置文件中添加如下地址：

mybatis:
  config-location: classpath:mybatis/mybatis-config.xml
  mapper-locations: classpath:mybatis/mapper/*.xml

在resources目录下建立一个mybatis文件夹，然后放置核心配置文件mybatis-config.xml，就可以读取xml文件中的配置了。

在resources/mapper目录下建立以.xml为结尾的映射文件，可以使用xml配置的方式，编写增删改查的语句。

但注意，对于同一个接口方法，使用注解或使用xml只能同时使用其中一种，否则就会报错。