SpringBoot整合Mybatis

SpringBoot整合mybatis的实现过程

一、SpringBoot整合mybatis的pom.xml文件，如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>cn.smilexl</groupId>
    <artifactId>springboot_mybatis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot_mybatis</name>
    <description>springboot整合mybatis</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- jdbc -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
         <!--mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.0</version>
        </dependency>
        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!--引入druid数据源-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.12</version>
        </dependency>
        <!--log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <!--test-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

二、相关步骤：

1、配置数据源相关属性（application.yml），数据源属性注入，见springboot整合druid章节；

server:
  port: 8081
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mybatis
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: 123456
    type: com.alibaba.druid.pool.DruidDataSource

#durid数据源属性
#   数据源其他配置
    initialSize: 5 #初始化连接个数
    minIdle: 5 #最小连接池数量
    maxActive: 20 #最大连接数量
    maxWait: 60000 #获取连接时最大等待时间，单位毫秒
    timeBetweenEvictionRunsMillis: 60000 #(1)Destroy线程会检测连接的间隔时间，(2)testWhileIdle的判断依据
    minEvictableIdleTimeMillis: 300000 #连接保持空闲而不被驱逐的最小时间
    validationQuery: SELECT 1 FROM DUAL #检测连接是否有效的sql，要求是一个查询语句
    testWhileIdle: true #申请连接的时候检测
    testOnBorrow: false #申请连接时执行validationQuery检测连接是否有效，做了这个配置会降低性能
    testOnReturn: false #归还连接时执行validationQuery检测连接是否有效，做了这个配置会降低性能
    poolPreparedStatements: true #是否缓存preparedStatement
#   配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
    filters: stat,wall,log4j
    maxPoolPreparedStatementPerConnectionSize: 20
    useGlobalDataSourceStat: true
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500

2、给数据库建表；

3、创建JavaBean（Employee.java、Department .java）；

//雇员信息实体类
public class Employee {
    private Integer id;
    private String lastName;
    private Integer gender;
    private String email;
    private Integer dId;

     getter、setter 方法省略......
}

//部门信息实体类
public class Department {
    private Integer id;
    private String departmentName;

  getter、setter 方法省略......
}

三、注解版（接口 DepartmentMapper.java ）

package cn.smilexl.springboot_mybatis.mapper;

import cn.smilexl.springboot_mybatis.entity.Department;
import org.apache.ibatis.annotations.*;

@Mapper //指定这是一个操作数据库的mapper
public interface DepartmentMapper {

    //根据id查询部门
    @Select("select * from department where id=#{id}")
    //mybatis中数据库不能自动识别大写字母，如userName，它只认识user_name，因此需要转换
//    @Results({
//            @Result(column = "department_name",property = "departmentName")
//    })
    public Department getDeptById(Integer id);

    //根据id删除部门
    @Delete("delete from department where id=#{id}")
    public int deleteDeptById(Integer id);

    //添加
    @Options(useGeneratedKeys = true, keyProperty = "id")//设置返回自增主键
    @Insert("insert into department(department_name) values (#{departmentName})")
    public int insetDept(Department department);

    //更新
    @Update("update department set department_name=#{departmentName} where id=#{id}")
    public int updateDept(Department department);
}

1、mybatis中驼峰命名问题：

（1）方法一：在dao方法上添加注解

   //根据id查询部门
    @Select("select * from department where id=#{id}")
    //mybatis中数据库不能自动识别大写字母，如userName，它只认识user_name，因此需要转换
    @Results({
            @Result(column = "department_name",property = "departmentName")
    })
    public Department getDeptById(Integer id);

（2）方法二：在yml配置文件中添加配置

# mybatis的相关配置
mybatis:
  configuration:
  #开启驼峰命名
    map-underscore-to-camel-case: true

2、使用MapperScan批量扫描所有的Mapper接口（启动类：SpringbootMybatisApplication .java）

//使用MapperScan批量扫描所有的Mapper接口；
@MapperScan(value = "cn.smilexl.springboot_mybatis.mapper")
@SpringBootApplication
public class SpringbootMybatisApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootMybatisApplication.class, args);
    }

}

四、配置版

使用@Mapper或者在启动类上使用@MapperScan(value="maper文件的位置")将接口扫描装配到容器中

1、在yml配置文件中添加mybatis的相关配置

#mybatis的相关配置
mybatis:
  #mapper配置文件
  mapper-locations: classpath:mapper/*.xml
  #开启驼峰命名
  configuration:
    map-underscore-to-camel-case: true

2、DAO层文件（EmployeeMapper.java）

package cn.smilexl.springboot_mybatis.mapper;
import cn.smilexl.springboot_mybatis.entity.Employee;

//@Mapper
public interface EmployeeMapper {
    //根据id查询
    public Employee getEmpById(Integer id);
    //添加
    public int insetEmp(Employee employee);
}

3、mapper映射文件（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="cn.smilexl.springboot_mybatis.mapper.EmployeeMapper">

    <!--根据id查询-->
    <select id="getEmpById" resultType="cn.smilexl.springboot_mybatis.entity.Employee">
      select * from employee where id = #{id}
    </select>

    <!--添加-->
    <insert id="insetEmp">
        insert into employee(last_name,email,gender,d_id) 
        values (#{lastName},#{email},#{gender},#{dId})
    </insert>

</mapper>

   文件所在位置：

-------------------- src
----------------------- |- main
-----------------------------|- resources
-------------------------------------|- mapper
-----------------------------------------|- EmployeeMapper.xml