Spring 全家桶之 Spring Boot 2.6.4- Data Access

一、Spring Boot 整合 MyBatis

MyBatis的自動配置

創建工程spring-boot-mybatis,創建項目時勾選MyBatis Framework會自動引入MyBatis的Starter

分析Mybatis的Staters啟動器依賴

MyBatis的自動配置類和配置項類都在autoconfigure包下

MyBatis自動配置類依賴了SqlSessionFactory和SqlSessionFactoryBean以及DataSource類,并且啟用了MyBatisProperties類中的屬性作為配置項,并且在DataSourceAutoConfiguration自動配置類和MybatisLanguageDriverAutoConfiguration類生效后才會生效。

MyBatisProperties類源碼中包含了mybatis的配置項

MyBatis的配置前綴都是以mybatis開頭

配置Druid數據源

引入driud

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

Druid數據源配置可以參考 Spring 全家桶之 Spring Boot 2.6.4(四)- Data Access(Part A JDBC)

初始化項目

在resources目錄下放置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目錄中創建兩個實體類Employee和Department對應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;}

配置自定義數據源初始化類,初始化數據源

@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;    }}

啟動應用,Spring Boot會自動在數據庫表創建,再次啟動之前如果不想初始化數據可以將@Configuration注解注釋掉

二、MyBatis注解方式的使用

創建DepartmentMapper接口,使用注解標注增刪改查的SQL語句

@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);}

創建DepartmentMapperTest測試類,測試DepartmentMapper中的增刪改查方法

@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);    }}

測試insert方法

測試selectOneById方法

MyBatis 配置駝峰命名轉換

修改Department表departmentName為下劃線形式department_name;再次執行selectOneById方法

查詢到DepartmentName屬性為空,這時可以在yml配置文件中開啟駝峰命名轉換

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

再次查詢既可以查詢到指定的是數據

配置類開啟駝峰命名轉換

也可以使用配置類來開啟駝峰命名轉換,MyBatisAutoConfuguration中包含了configurationCustomizers屬性,這是一個List列表,包含了所有的自定義配置

而ConfigurationCustomizer接口中有一個customize方法,該方法傳入Configuration自定義配置

Configuration類中的屬性就是可以自定義的配置

在config包下新建LilithMyBatisConfig配置類,新增一個configurationCustomizer方法,既往容器中注入ConfigurationCustomizer設置了屬性的實現類

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

這里使用lambda表達式實現了ConfigurationCustomizer接口中的customize方法

將yml文件中的駝峰命名轉換注釋,重新執行selectOneById方法

可以成功查詢出數據。

@Mapper注解

@Mapper注解是自動配置的關鍵,標記當前類為容器的一個組件,缺少@Mapper注解將無法啟動。

當Mapper接口非常多是,給每一個Mapper接口增加@Mapper注解非常麻煩,可以在主啟動類上使用@MapperScan注解,掃描所有的Mapper接口

三、MyBatis配置文件方式的使用

創建Mapper接口EmployeeMapper,需要說明的是無論是注解還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目錄下創建mappers文件夾,新增EmployeeMapper.xml文件,增加Mapper接口中selectOneById方法和insert方法對應的SQL語句

<?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

書寫測試類

@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);    }}

執行插入方法

錯誤提示config-location和configuration不能同時寫在yml文件中; 在resources目錄下新建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>

再次執行測試

控制臺顯示有1行成功更新,數據被成功插入到輸入句酷表中

執行selectOneById方法

成功查詢出insert方法插入的數據