一、Spring Boot 整合 MyBatis

MyBatis的自动配置

创建工程spring-boot-mybatis,创建项目时勾选MyBatis Framework会自动引入MyBatis的Starter

分析Mybatis的Staters启动器依赖

MyBatis的自动配置类和配置项类都在autoconfigure包下

MyBatis自动配置类依赖了SqlSessionFactory和SqlSessionFactoryBean以及DataSource类,并且启用了MyBatisProperties类中的属性作为配置项,并且在DataSourceAutoConfiguration自动配置类和MybatisLanguageDriverAutoConfiguration类生效后才会生效。

MyBatisProperties类源码中包含了mybatis的配置项

MyBatis的配置前缀都是以mybatis开头

配置Druid数据源

引入driud

<dependency>    <groupId>com.alibaba</groupId>    <artifactId>druid-spring-boot-starter</artifactId>    <version>1.2.8</version></dependency>

Druid数据源配置可以参考 Spring 全家桶之 Spring Boot 2.6.4(四)- Data Access(Part A JDBC)

初始化项目

在resources目录下放置employee.sql和department.sql文件

SET FOREIGN_KEY_CHECKS=0;-- ------------------------------ Table structure for employee-- ----------------------------drop TABLE IF EXISTS `employee`;CREATE TABLE `employee` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `lastName` varchar(255) DEFAULT NULL,  `email` varchar(255) DEFAULT NULL,  `gender` int(2) DEFAULT NULL,  `d_id` int(11) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

SET FOREIGN_KEY_CHECKS=0;-- ------------------------------ Table structure for department-- ----------------------------drop TABLE IF EXISTS `department`;CREATE TABLE `department` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `departmentName` varchar(255) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

entity目录中创建两个实体类Employee和Department对应employee表和Department表

@Datapublic class Employee {    private Integer id;    private String lastName;    private String email;    private Integer gender;    private Integer dId;}

@Datapublic class Department {    private Integer id;    private String departmentName;}

配置自定义数据源初始化类,初始化数据源

@Configurationpublic class LilithDataSourceInitializer {    @Value("classpath:employee.sql")    private Resource employee;    @Value("classpath:department.sql")    private Resource department;    @Bean    public DataSourceInitializer dataSourceInitializer(final DataSource dataSource){        final DataSourceInitializer initializer = new DataSourceInitializer();        initializer.setDataSource(dataSource);        initializer.setDatabasePopulator(databasePopulator());        return initializer;    }    private DatabasePopulator databasePopulator(){        final ResourceDatabasePopulator populator = new ResourceDatabasePopulator();        populator.addScripts(employee,department);        return populator;    }}

启动应用,Spring Boot会自动在数据库表创建,再次启动之前如果不想初始化数据可以将@Configuration注解注释掉

二、MyBatis注解方式的使用

创建DepartmentMapper接口,使用注解标注增删改查的SQL语句

@Mapperpublic interface DepartmentMapper {    @select("select * FROM department WHERE id = #{id}")    Department selectOneById(Integer id);    @delete("delete FROM department WHERE id = #{id}")    void deleteOneById(Integer id);    @insert("insert INTO department (department_name) VALUES (#{departmentName})")    void insert(Department department);    @update("update department SET department_name = #{departmentName} where id = #{departmentId}")    void update(Department department);}

创建DepartmentMapperTest测试类,测试DepartmentMapper中的增删改查方法

@SpringBootTestpublic class DepartmentMapperTest {    @Resource    private DepartmentMapper departmentMapper;    @Test    public void selectOneById() {        Department department = departmentMapper.selectOneById(1);        System.out.println(department);    }    @Test    public void insert() {        Department department = new Department();        department.setDepartmentName("Avengers");        departmentMapper.insert(department);    }}

测试insert方法

测试selectOneById方法

MyBatis 配置驼峰命名转换

修改Department表departmentName为下划线形式department_name;再次执行selectOneById方法

查询到DepartmentName属性为空,这时可以在yml配置文件中开启驼峰命名转换

mybatis:  configuration:    map-underscore-to-camel-case: true

再次查询既可以查询到指定的是数据

配置类开启驼峰命名转换

也可以使用配置类来开启驼峰命名转换,MyBatisAutoConfuguration中包含了configurationCustomizers属性,这是一个List列表,包含了所有的自定义配置

而ConfigurationCustomizer接口中有一个customize方法,该方法传入Configuration自定义配置

Configuration类中的属性就是可以自定义的配置

在config包下新建LilithMyBatisConfig配置类,新增一个configurationCustomizer方法,既往容器中注入ConfigurationCustomizer设置了属性的实现类

@Configurationpublic class LilithMyBatisConfig {        @Bean    public ConfigurationCustomizer configurationCustomizer(){        return configuration -> configuration.setMapUnderscoreToCamelCase(true);    }}

这里使用lambda表达式实现了ConfigurationCustomizer接口中的customize方法

将yml文件中的驼峰命名转换注释,重新执行selectOneById方法

可以成功查询出数据。

@Mapper注解

@Mapper注解是自动配置的关键,标记当前类为容器的一个组件,缺少@Mapper注解将无法启动。

当Mapper接口非常多是,给每一个Mapper接口增加@Mapper注解非常麻烦,可以在主启动类上使用@MapperScan注解,扫描所有的Mapper接口

三、MyBatis配置文件方式的使用

创建Mapper接口EmployeeMapper,需要说明的是无论是注解还是配置文件方式使用MyBatis,@Mapper注解或者@MapperScan注解都是必不可少的。

@Mapperpublic interface EmployeeMapper {    void insert(Employee employee);    Employee selectOneById(Integer id);}

在resources目录下创建mappers文件夹,新增EmployeeMapper.xml文件,增加Mapper接口中selectOneById方法和insert方法对应的SQL语句

<?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.lilith.mybatis.mapper.EmployeeMapper">    <select  resultType="com.lilith.mybatis.entity.Employee">        select * from employee where id = #{id}    </select>    <insert  useGeneratedKeys="true" keyProperty="id" keyColumn="id">        insert INTO employee (last_name, email, gender, d_id)        VALUES (#{lastName}, #{email}, #{gender},#{dId})    </insert>    </mapper>

yml中增加mybatis配置

mybatis:  # 全局配置文件的位置  config-location: classpath:mybatis-config.xml  mapper-locations: classpath:mappers/*.xml  configuration:    map-underscore-to-camel-case: true

书写测试类

@SpringBootTestpublic class EmployeeMapperTest {    @Resource    private EmployeeMapper employeeMapper;    @Test    public void insert() {        Employee employee = new Employee();        employee.setLastName("Thanos");        employee.setEmail("thanos@gmail.com");        employee.setGender(1);        employee.setDId(1);        employeeMapper.insert(employee);    }    @Test    public void selectOneById() {        Employee employee = employeeMapper.selectOneById(1);        System.out.println(employee);    }}

执行插入方法

错误提示config-location和configuration不能同时写在yml文件中; 在resources目录下新建MyBatis全局配置文件,把configuration配置到mybatis-config.xml全局配置文件中

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE configuration        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"        "http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration>    <settings>        <setting name="mapUnderscoreToCamelCase" value="true"/>    </settings></configuration>

再次执行测试

控制台显示有1行成功更新,数据被成功插入到输入句酷表中

执行selectOneById方法

成功查询出insert方法插入的数据