1、前言java
Orm框架的本質是簡化編程中操做數據庫的編碼,發展到如今,基本上就剩宣稱不用謝一句sql的hibernate,一個是能夠靈活調試動態sql的mybatis,二者各有特色,在企業級系統來發中能夠根據需求靈活使用。發現一個有趣的現象:傳統企業大都喜歡hibernate,互聯網行業一般使用mybatis。web
hibernate特色就是全部的sql都用java代碼來生成,不用跳出程序去寫sql,有這編程的完整性,發展到最頂端就是spring data jpa這種模式,基本上根據方法名就能夠生成對應的sql。spring
mybatis初期使用比較麻煩,須要各類配置文件、實體類、Dao層映射關係、還有一大堆其餘配置文件。sql
固然mybatis也有發現了這種弊端,初期開發了generator能夠根據表結構自動生成實體類、配置文件和dao層代碼,能夠減輕一部分開發量;後期也進行了大量的優化可使用註解,自動管理dao層和配置文件等,發展到最頂級就是今天講的這種springboot+mybatis能夠徹底註解不用配置文件,也能夠簡單配置輕鬆上手。數據庫
springboot就是牛逼呀,啥玩意關聯springboot都能化繁爲簡。apache
2、mybatis-spring-boot-starter編程
mybatis-spring-boot-starter主要由兩種解決方案,一種是使用註解解決一切問題,一種的簡化後的老傳統。瀏覽器
固然任何模式都須要先引入mybatis-spring-boot-starter的pom文件,如今最新版本是springboot
<dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>2.1.1</version> </dependency>
3、無配置註解版mybatis
一、添加maven文件
<dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jdbc</artifactId> </dependency> <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>2.1.1</version> </dependency> <dependency> <groupId>com.oracle.ojdbc</groupId> <artifactId>ojdbc8</artifactId> <scope>runtime</scope> </dependency> <!-- https://mvnrepository.com/artifact/com.alibaba/druid --> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.1.21</version> </dependency> <!-- https://mvnrepository.com/artifact/log4j/log4j --> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> </dependency> </dependencies>
二、application.yml添加相關配置
spring: datasource: username: mine password: mine url: jdbc:oracle:thin:@127.0.0.1:1521:orcl driver-class-name: oracle.jdbc.driver.OracleDriver type: com.alibaba.druid.pool.DruidDataSource initialSize: 5 minIdle: 5 maxActive: 20 maxWait: 60000 timeBetweenEvictionRunsMillis: 60000 minEvictableIdleTimeMillis: 300000 validationQuery: SELECT 1 FROM DUAL testWhileIdle: true testOnBorrow: false testOnReturn: false poolPreparedStatements: true filters: stat,wall,log4j maxPoolPreparedStatementPerConnectionSize: 20 useGlobalDataSourceStat: true connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500
Spring Boot 會自動加載spring.datasource.*相關配置,數據源就會自動注入到 sqlSessionFactory 中,sqlSessionFactory 會自動注入到 Mapper 中,對了,你一切都不用管了,直接拿起來使用就好了。
在啓動類中添加對 mapper 包掃描@MapperScan
@MapperScan(value="com.demo.mapper") @SpringBootApplication public class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } }
或者直接在 Mapper 類上面添加註解@Mapper,建議使用上面那種,否則每一個 mapper 加個註解也挺麻煩的
三、controller
@RestController public class DeptController { @Autowired DepartmentMapper departmentMapper; @GetMapping("/dept/{id}") public Department getDepartment(@PathVariable("id") Integer id){ return departmentMapper.getDeptById(id); } @GetMapping("/dept") public int insertDeptById(@PathVariable("id") Integer id,@PathVariable("departmentName") String departmentName){ int ret = departmentMapper.insertDept(id,departmentName); return ret; } }
四、開發mapper
package com.demo.mapper; import com.demo.bean.Department; import org.apache.ibatis.annotations.*; public interface DepartmentMapper { @Select("select * from SSH_DEPARTMENT where id=#{id}") public Department getDeptById(Integer id); @Delete("delete from SSH_DEPARTMENT where id=#{id}") public int deleteDeptById(Integer id); @Options(useGeneratedKeys = true,keyProperty = "id") @Insert("insert into SSH_DEPARTMENT(department_name) values(#{departmentName})") public int insertDept(Department department); @Update("update SSH_DEPARTMENT set departmentName=#{DEPARTMENT_NAME} where id=#{id}") public int updateDept(Department department); }
四、運行
上面三步就基本完成了相關 Mapper 層開發,使用的時候看成普通的類注入進入就能夠了
(1)查詢
(2)插入
4、極簡XML版本
極簡 xml 版本保持映射文件的老傳統,接口層只須要定義空方法,系統會自動根據方法名在映射文件中找對應的 Sql
一、配置
pom 文件和上個版本同樣,只是application.yml新增如下配置
mybatis.config-location=classpath:mybatis/mybatis-config.xml mybatis.mapper-locations=classpath:mybatis/mapper/*.xml
mybatis-config.xml 配置
<?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>
二、employeeMapper.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.atguigu.springboot.mapper.EmployeeMapper"> <!-- public Employee getEmpById(Integer id); public void insertEmp(Employee employee);--> <select id="getEmpById" resultType="com.atguigu.springboot.bean.Employee"> SELECT * FROM employee WHERE id=#{id} </select> <insert id="insertEmp"> INSERT INTO employee(lastName,email,gender,d_id) VALUES (#{lastName},#{email},#{gender},#{dId}) </insert> </mapper>
三、開發mapper
package com.demo.mapper; import com.demo.bean.Employee; import org.mybatis.spring.annotation.MapperScan; @MapperScan public interface EmployeeMapper { public Employee getEmpById(Integer id); public void insertEmp(Employee employee); }
對比上一步,這裏只須要定義接口方法。
四、運行結果與註解方式無異。
5、兩種模式如何選擇
兩種模式各有特色,註解版適合簡單快速的模式,其實像如今流行的這種微服務模式,一個微服務就會對應一個本身的數據庫,多表鏈接查詢的需求會大大的下降,會愈來愈適合這種模式。
老傳統模式比較適合大型項目,能夠靈活的動態生成sql,方便調整sql,有的人就是愛寫sql,再配上點存儲過程,越複雜越好,感受本身越牛,那你就用這個。