SpringBoot整合mybatis
一. 创建一个SpringBoot项目
二. 项目结构
注意springboot的启动类的位置
三. 配置文件
(1) 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 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>demo2</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo2</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<!-- web核心依赖 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- lombok 插件 简化代码 -->
<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>
<!--mybatis-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.1.0</version>
</dependency>
<!--mysql数据库驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</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>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
<configuration>
<skipTests>true</skipTests>
</configuration>
</plugin>
</plugins>
<!-- 如果不添加此节点mybatis的mapper.xml文件都会被漏掉。 -->
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.yml</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>
</project>
pom.xml 配置吃过的亏：
a. mybatis-plus 依赖
报错：
java.lang.annotation.AnnotationFormatError: Invalid default: public abstract java.lang.Class org.mybatis.spring.annotation.MapperScan.factoryBean()
at java.lang.reflect.Method.getDefaultValue(Method.java:612) ~[na:1.8.0_92]
SpringMVC的引入方式：
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus</artifactId>
<version>3.1.0</version>
</dependency>
SpringBoot的引入方式：
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.1.0</version>
</dependency>
还有一点要注意的是：
引入 MyBatis-Plus 之后请不要再次引入 MyBatis 以及 MyBatis-Spring，以避免因版本差异导致的问题。
b. 配置resource
如果不添加此节点mybatis的mapper.xml文件都会被漏掉。
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.yml</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
注：<resources> 要放在 <build> 里面
(2) application.yml
server:
port: 8080
spring:
datasource:
username: root
password: 123
url: jdbc:mysql:///myschool
driver-class-name: com.mysql.cj.jdbc.Driver
#mybatis-plus配置
mybatis-plus:
mapper-locations: classpath:mapping/*.xml
#showSql
logging:
level:
com:
example:
mapper : debug
mybatis-plus的扫描路径也可以在pom.xml里面写：
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>com.lv.mybatis.dao.xml/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
这一段没有起到作用，我把 UserMapper.xml 放在 resources/mapping下面的话，就是不知道为什么和 UserMapper 映射不了
这样不行 ‘最后还是改成这样才可以
四. 使用 mybatis-plus
-
pom.xml 添加依赖
-
application.yml 设置数据库连接 和 配置mybatis
-
写 po 实体类
import lombok.Data; @Data public class Users { private long id; private String username; private String password; } -
写 mapper 接口类
//@Mapper @Repository public interface UserMapper extends BaseMapper<Users> { /** * BaseMapper 里封装了一些常用的 CRUD * 直接继承 BaseMapper 可以省去xml的编写 */ /** * 当然也可以通过 xml 自定义 sql 查询语句 */ // 该方法使用User实体类 public List<Users> getAllUser(); }a. 继承 BaseMapper
b. 写自己的操作数据的方法
c. 可选注解
@Mapper
@Repository：需要在启动类加上
@MapperScan("com.example.demo2.mapper")//指向你的mapper接口类 -
写 mapper.xml
<?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.example.demo2.mapper.UserMapper">
<select id="getAllUser" resultType="com.example.demo2.po.Users">
SELECT * FROM users
</select>
</mapper>
注意 namespace id resultType
-
mapper接口和mapper.xml文件的映射（很重要）
https://blog.csdn.net/weixin_44695793/article/details/107752054