Spring Boot-甜蜜的整合MyBatis&注解方式&配置方式

前言

整合Mybtis對于Spring Boot來說,是非常簡單的, 通過這一篇文章, 你可以無壓力快速入門,不過開始之前我要說一下我的版本信息:

• maven 3.2.5

• jdk 1.8

• Spring Boot 2.1.6

創建項目

依然是使用idea的自動化配置, 不過這里,我們需要勾選以下依賴:

如果你勾選了 MyBatis , 你會發現你的pom文件里有 :

		<dependency>
?<groupId>org.mybatis.spring.boot</groupId>
?<artifactId>mybatis-spring-boot-starter</artifactId>
?<version>2.1.0</version>
?</dependency>

這條依賴

只要是帶 *-spring-boot-starter的,都是Spring Boot官方推薦的, 這里的mybatis就是, 讓我們來看一下mybatis包下的所有包:

我們發現它引入了, mybatis-spring 的包等等,以及還有mybatis-spring-boot-autoconfigure, 這個是自動配置的意思, 對于Spring Boot來說,自動配置是一大特點

配置Druid數據源

Spring Boot2.x的數據源 hikari 的, 而1.x則是 Tomcat的, 所以我們要配置以下自己的數據源

?<dependency>
?<groupId>com.alibaba</groupId>
?<artifactId>druid</artifactId>
?<version>1.1.16</version>
?</dependency>

引入這個依賴就好了

然后在 application.yml 配置文件下:

spring:
?datasource:
?password:?root
?username:?root
?url:?jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC
?driver-class-name:?com.mysql.cj.jdbc.Driver
?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
?#?配置監控統計攔截的filters，去掉后監控界面sql無法統計，'wall'用于防火墻
?filters:?stat,wall,log4j
?maxPoolPreparedStatementPerConnectionSize:?20
?useGlobalDataSourceStat:?true
?connectionProperties:?druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500

下面這一堆的屬性是不生效的, 如果想要生效, 需要特殊配置一下, Druid監控也配置了:

package?com.carson.config;
import?com.alibaba.druid.pool.DruidDataSource;
import?com.alibaba.druid.support.http.StatViewServlet;
import?com.alibaba.druid.support.http.WebStatFilter;
import?org.springframework.boot.context.properties.ConfigurationProperties;
import?org.springframework.boot.web.servlet.FilterRegistrationBean;
import?org.springframework.boot.web.servlet.ServletRegistrationBean;
import?org.springframework.context.annotation.Bean;
import?org.springframework.context.annotation.Configuration;
import?javax.sql.DataSource;
import?java.util.Arrays;
import?java.util.HashMap;
import?java.util.Map;
@Configuration
public?class?DruidConfig?{
?@ConfigurationProperties(prefix?=?"spring.datasource")
?@Bean
?public?DataSource?druid()?{
?return?new?DruidDataSource();
?}
?//?配置?Druid?監控
?//1)?配置一個管理后臺的Servlet
?@Bean
?public?ServletRegistrationBean?statViewServlet()?{
?ServletRegistrationBean?bean?=?new?ServletRegistrationBean(new?StatViewServlet(),?"/druid/*");
?Map<String,?String>?initParams?=?new?HashMap<>();
?//?這里是?druid?monitor(監視器)的?賬號密碼,?可以任意設置
?initParams.put("loginUsername",?"admin");
?initParams.put("loginPassword",?"123456");
?initParams.put("allow",?"");
?initParams.put("deny",?"192.123.11.11");
?//?設置初始化參數
?bean.setInitParameters(initParams);
?return?bean;
?}
?//?2)配置一個監控的?filter
?@Bean
?public?FilterRegistrationBean?webStatFilter()?{
?FilterRegistrationBean?bean?=?new?FilterRegistrationBean();
?bean.setFilter(new?WebStatFilter());
?Map<String,?String>?initParams?=?new?HashMap<>();
?initParams.put("exclusions","*.js,*.css,/druid/*");
?bean.setInitParameters(initParams);
?bean.setUrlPatterns(Arrays.asList("/*"));
?return?bean;
?}
}

啟動主類, 查看是否可以進入到?德魯伊監視器, 如果你報錯了請添加 log4j 依賴:

?<dependency>
?<groupId>log4j</groupId>
?<artifactId>log4j</artifactId>
?<version>1.2.17</version>
?</dependency>
<!--我也不清楚為什么,?不加log4j的話就會報錯-->

查看效果:

利用SpringBoot建表

然后在 resources/sql 下引入兩個建表的sql文件:

• department.sql:

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;

• employee.sql:

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;

并且在 application.yml 文件下寫入:

?schema:
?-?classpath:sql/department.sql
?-?classpath:sql/employee.sql
?initialization-mode:?always

schema`是與 password/username 等等同級的,哦對了, 如果你是 springboot 2.x版本以上的, 你可能需要加上initialization-mode這個屬性。

運行主類, 查看是否建表成功,

如果你的程序在設置sql文件后 啟動報錯了:

• 重啟 idea (重啟大法好啊!)

• 查看 schema是否配置對了 sql文件的名字

• schema:

• -(空格)classpath:sql/xxx.sql

• 注意格式

對應數據庫實體類

• Employee.java

package?com.carson.domain;
public?class?Employee?{
?private?Integer?id;
?private?String?lastName;
?private?Integer?gender;
?private?String?email;
?private?Integer?dId;
?public?Integer?getId()?{
?return?id;
?}
?public?void?setId(Integer?id)?{
?this.id?=?id;
?}
?public?String?getLastName()?{
?return?lastName;
?}
?public?void?setLastName(String?lastName)?{
?this.lastName?=?lastName;
?}
?public?Integer?getGender()?{
?return?gender;
?}
?public?void?setGender(Integer?gender)?{
?this.gender?=?gender;
?}
?public?String?getEmail()?{
?return?email;
?}
?public?void?setEmail(String?email)?{
?this.email?=?email;
?}
?public?Integer?getdId()?{
?return?dId;
?}
?public?void?setdId(Integer?dId)?{
?this.dId?=?dId;
?}
}

• Department.java

package?com.carson.domain;
public?class?Department?{
?private?Integer?id;
?private?String?departmentName;
?public?Integer?getId()?{
?return?id;
?}
?public?void?setId(Integer?id)?{
?this.id?=?id;
?}
?public?String?getDepartmentName()?{
?return?departmentName;
?}
?public?void?setDepartmentName(String?departmentName)?{
?this.departmentName?=?departmentName;
?}
}

記得把剛才我配置文件的 schema屬性全部注釋掉, 我們不希望下次運行的時候會再次創建表

數據庫交互

- 注解版

• 建立一個 Mapper, 把sql語句直接寫在上面

package?com.carson.mapper;
import?com.carson.domain.Department;
import?org.apache.ibatis.annotations.*;
//?指定這是一個?mapper
@Mapper
public?interface?DepartmentMapper?{
?@Select("select?*?from?department?where?id=#{id}")
?public?Department?getDepById(Integer?id);
?@Delete("delete?from?department?where?id=#{id}")
?public?int?deleteDepById(Integer?id);
?@Insert("insert?into?department(departmentName)?values(#{departmentName})")
?public?int?insertDept(Department?department);
?@Update("update?department?set?departmentName=#{departmentName}?where?id=#{id}")
?public?int?updateDept(Department?department);
}

然后寫一個Controller :

package?com.carson.controller;
import?com.carson.domain.Department;
import?com.carson.mapper.DepartmentMapper;
import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.web.bind.annotation.GetMapping;
import?org.springframework.web.bind.annotation.PathVariable;
import?org.springframework.web.bind.annotation.RestController;
@RestController?//?代表返回?json?數據的?controller
public?class?DeptController?{
?@Autowired
?DepartmentMapper?departmentMapper;
?@GetMapping("/dept/{id}")
?public?Department?getDept(@PathVariable("id")?Integer?id)?{
?return?departmentMapper.getDepById(id);
?}
?@GetMapping
?public?Department?inserDept(Department?department)?{
?departmentMapper.insertDept(department);
?return?department;
?}
}

• 通過?@PathVariable?可以將?URL?中占位符參數綁定到控制器處理方法的入參中：URL 中的 {xxx} 占位符可以通過@PathVariable(“xxx“) 綁定到操作方法的入參中。

啟動主類, 輸入這個: localhost:8080/dept?departmentName=AA , 這是往數據庫增加一條數據:

然后查詢: localhost:8080/dept/3 , 我數據庫id是3, 所以我要查詢3:

不過發現一個問題, 在插入數據的時候獲取不到 id:

所以我們要使用一個@Options注解:

?@Options(useGeneratedKeys?=?true,keyProperty?=?"id")
?@Insert("insert?into?department(departmentName)?values(#{departmentName})")
?public?int?insertDept(Department?department);

添加到剛才 mapper中insert 的 @value注解上面

• useGeneratedKeys : 使用生成的主鍵

• keyProperty: 意思是 Department 里面的哪個屬性是主鍵, 就是我們的 id

試著插入一條數據:

但是實際忘記注釋掉 schema , 導致每次運行都會重新創建數據庫, 各位要注意

還有一個問題

我們把數據庫的字段名改成 department_name 而實體類是departmentName;

并且把sql語句也改正

?@Options(useGeneratedKeys?=?true,keyProperty?=?"id")
?@Insert("insert?into?department(department_name)?values(#{departmentName})")
?public?int?insertDept(Department?department);
?@Update("update?department?set?department_name=#{departmentName}?where?id=#{id}")
?public?int?updateDept(Department?department);

然后在進行查詢操作的話:

我們發現獲取不到 departmentName 了, 以前Spring 我們是使用配置文件來應對這種情況的, 但是我們現在沒有了xml文件,我們該怎么辦呢?

世上無難事

創建自定義配置類:

package?com.carson.config;
import?org.mybatis.spring.boot.autoconfigure.ConfigurationCustomizer;
import?org.springframework.context.annotation.Bean;
import?org.springframework.context.annotation.Configuration;
@Configuration
public?class?MyBatisConfig?{
?@Bean
?public?ConfigurationCustomizer?configurationCustomizer()?{
?return?new?ConfigurationCustomizer()?{
?@Override
?public?void?customize(org.apache.ibatis.session.Configuration?configuration)?			?{
?configuration.setMapUnderscoreToCamelCase(true);
?}
?};
?}
}

注意這里面的 setMapUnderscoreToCamelCase,意思是:

翻譯大法好啊, 我的英文太差了, 再次訪問 http://localhost:8080/dept/1 查詢操作, 我發現已經不是 null了:

{"id":1,"departmentName":"jackMa"}

馬總正確的展現出來了!

MapperScan注解

掃描器, 用來掃描mapper接口的

我把它標記到 啟動類 上(你可以標記在任何地方):

指定一個包,它會掃描這個包下所有的 mapper 接口, 防止你的mapper文件太多, 并且忘記加 @mapper 注解, 這樣可以提高正確性

- 配置文件版

注解版貌似很方便, 但是如果遇到復雜的sql , 比如動態sql等等, 還是需要用 xml 配置文件的;

創建一個 Employee 的Mapper接口:

package?com.carson.mapper;
import?com.carson.domain.Employee;
public?interface?EmployeeMapper?{
?public?Employee?getEmpById(Integer?id);
?public?void?insertEmp(Employee?employee);
}

在 resources/mybatis 下創建一個 mybatis-config.xml 全局配置文件:

<?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>
</configuration>

在 resources/mybatis/mapper 包下創建 EmployeeMapper.xml 映射文件:

<?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">
<!--?綁定接口?并且寫兩條?SQL?語句-->
<mapper?namespace="com.carson.mapper.EmployeeMapper">
?<select?id="getEmpById"?resultType="com.carson.domain.Employee">
?select?*?from?employee?where?id?=?#{id}
?</select>
?<insert?id="insertEmp">
?insert?into?employee(lastName,email,gender,d_id)?values?(#{lastName},	?		#{email},#{gender},#{d_id})
?</insert>
</mapper>

然后再 application.yml 配置文件下添加一條配置:

#?mybatis屬性是跟?spring?屬性平級的,?千萬不要把格式搞錯
mybatis:
#?指定全局配置文件
?config-location:?classpath:mybatis/mybatis-config.xml
#?指定?mapper?映射文件,?*?代表所有?
?mapper-locations:?classpath:mybatis/mapper/*.xml

讓我們在剛才的DeptController類里添加一段 Controller :

?@Autowired
?EmployeeMapper?employeeMapper
?
?@GetMapping("emp/{id}")
?public?Employee?getEmp(@PathVariable("id")?Integer?id)?{
?return?employeeMapper.getEmpById(id);
?}

啟動主類訪問一下 localhost:8080/emp/1 , 查看結果:

我們發現 dId沒有查詢出來, 這是因為 數據庫字段是 d_id , 而java里是 dId , 所以我們要像剛才注解版一樣, 配置一樣東西, 讓我們打開 mapper全局配置文件添加:

<?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>

mapUnderscoreToCamelCase : 是否開啟自動駝峰命名規則（camel case）映射，即從經典數據庫列名 A_COLUMN 到經典 Java 屬性名 aColumn 的類似映射。

再次試驗:

可以看出已經成功了

無論是哪種版本. 要根據自己的實際情況來定, 注解雖然方便, 但是復雜業務的就不行了