SpringBoot整合Mybatis入门一看就懂

引入pom依赖：

• Mybatis依赖、数据库驱动依赖、数据库连接池依赖

<dependencies>
	<dependency>
    	<groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.1.1</version>
    </dependency>
    <dependency>
    	<groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
    	<groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.1.19</version>
    </dependency>
</dependencies>

创建数据库、编写与数据库字段一一对应的实体类

• 创建数据库举例

CREATE TABLE t_user(
	id VARCHAR(40) PRIMARY KEY,
	username VARCHAR(40),
	realname VARCHAR(40),
	password VARCHAR(40),
	sex VARCHAR(8)
);


CREATE TABLE t_emp(
	id VARCHAR(40) PRIMARY KEY,
	name VARCHAR(60),
	salary DOUBLE(7,2),
	bir date
);

• 连接数据库的数据源配置

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/ems_thymeleaf?serverTimezone=GMT
spring.datasource.username=root
spring.datasource.password=123456

• 配置**Mapper.xml的位置信息

mybatis.mapper-locations=classpath:com/example/demo/mapper/*.xml

• 用户类和员工类举例

@Data 
@AllArgsConstructor  //全参构造
@NoArgsConstructor  //无参构造
public class User{
    private String id;
    private String username;
    private String realname;
    private String password;
    private String sex;
}

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Emp{
    private String id;
    private String name;
    private Double salary;
    private Date bir;
}

• 注解的作用

1. @Data 加了这个注解主要是为了让实体类的代码更加简洁，这样子就不用生成getter、setter还有toString方法
2. @AllArgsConstructor 提供了类的全参构造
3. @NoArgsConstructor 提供类的无参构造

• 以上3个注解都要引入lombok依赖,引入方法如下

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.4</version>
    <scope>provided</scope>
</dependency>

编写DAO层接口（或者Mapper）

• DAO 以保存一个用户为例

public interface UserDAO {
    void save(User user);
}

对应的UserDAOMapper.xml写法

<?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.demo.dao.UserDAO">
    <!--注册-->
    <insert id="save" parameterType="com.example.demo.entity.User">
        insert into t_user values(#{id},#{username},#{realname},#{password},#{sex})
    </insert>
</mapper>