三、整合MyBatis

1.引入mybatis-starter(mybatis-spring-boot-starter)依赖

<dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.1.1</version>
    </dependency>

依赖关系图

2.配置数据源的相关属性（见上篇博客整合Druid）

1.引入druid数据源找到对应版本的druid依赖导入

<!--引入druid数据源-->
<!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
<dependency>
     <groupId>com.alibaba</groupId>
     <artifactId>druid</artifactId>
     <version>1.1.21</version>
</dependency>

2.配置文件引用上一篇博客整合Druid的配置文件

spring:
  datasource:
    username: root
    password: 1234567890
    url: jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8
    driver-class-name: com.mysql.jdbc.Driver
    initialization-mode: always
    #数据源的其他配置
    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,slf4j
    maxPoolPreparedStatementPerConnectionSize: 20
    useGlobalDataSourceStat: true
    connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500
#    schema:
#      - classpath:sql/department.sql
#      - classpath:sql/employee.sql
mybatis:
    config-location: classpath:mybatis/mybatis-config.xml
    mapper-locations: classpath:mybatis/mapper/*.xml

3.编写配置类将数据源进行配置

package com.atorg.springboot.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")//生效的配置文件是从配置文件的spring.datasource开始
    @Bean
    public DataSource druid(){
        return new DruidDataSource();
    }
    //配置druid监控
    //1.配置管理后台的servlet
    @Bean
    public ServletRegistrationBean statViewServlet(){
        ServletRegistrationBean bean=new ServletRegistrationBean(new StatViewServlet(),"/druid/*");
        Map<String,String> initParams =new HashMap<>();
        initParams.put("loginUsername","admin");
        initParams.put("loginPassword","123456");
        initParams.put("allow", "");//默认允许所有
        initParams.put("deny", "192.168.43.177");
        bean.setInitParameters(initParams);
        return bean;
    }
    //2.配置一个监控的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;
    }
}

3.给数据库建表

department.sql文件

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;

1.在配置文件中说明建表sql文件的位置(启动程序自动创建数据表)

schema:
  - classpath:sql/department.sql
  - classpath:sql/employee.sql

注意，数据表在程序运行开始就会自动创建，所以运行一次以后就将此建表语句删除，防止运行一次新建一次数据表

4.创建java bean进行数据封装

Department .class

package com.atorg.springboot.bean;

public class Department {
    private Integer id;

    private String departmentName;
    public Integer getId() {
        return id;
    }

    public String getDepartmentName() {
        return departmentName;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public void setDepartmentName(String departmentName) {
        this.departmentName = departmentName;
    }
}

Employee.class

package com.atorg.springboot.bean;

public class Employee {
    private Integer id;
    private String lastName;
    private Integer gender;
    private String email;
    private Integer dId;

    public Integer getId() {
        return id;
    }

    public String getLastName() {
        return lastName;
    }

    public Integer getGender() {
        return gender;
    }

    public String getEmail() {
        return email;
    }

    public Integer getdId() {
        return dId;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public void setGender(Integer gender) {
        this.gender = gender;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public void setdId(Integer dId) {
        this.dId = dId;
    }
}

5.使用MyBatis对数据库进行增删改查（MyBatis注解版）

1.编写Mapper类对数据库进行增删改查

package com.atorg.springboot.mapper;


import com.atorg.springboot.bean.Department;
import org.apache.ibatis.annotations.*;

//指定这是一个操作数据库的mapper
@Mapper           //如果不标明Mapper，MyBatis就无法工作
public interface DepartmentMapper {
    //数据库查询字段
    @Select("select * from department where id=#{id}")
    public Department getDeptById(Integer id);
    //数据库删除字段
    @Delete("delete from department where id=#{id}")
    public int deleteDeptById(Integer id);
    //数据库信息插入
    @Options(useGeneratedKeys = true,keyProperty = "id")   //指定那个是自增主键，不写这句在插入数据时id会显示null
    @Insert("insert into department(department_name) values(#{departmentName})")
    public int insertDept(Department department);
    //数据库字段信息更新
    @Update("update department set department_name=#{departmentName} where id=#{id}")
    public int updateDept(Department department);
}

如果我们的Mapper类特别多的情况下，在每一个类上都添加Mapper注解就太麻烦了，此时我们可以在主配置类上添加一下注解
MapperScan：批量扫描所有的Mapper接口

    @MapperScan(value = "com.atorg.springboot.mapper")        //指定添加@Mapper注解的类的位置，主动给其类上添加@Mapper注解，不用我们一个一个去添加

2.编写controller进行测试

DeptController.class

package com.atorg.springboot.controller;

import com.atorg.springboot.bean.Department;
import com.atorg.springboot.bean.Employee;
import com.atorg.springboot.mapper.DepartmentMapper;
import com.atorg.springboot.mapper.EmployeeMapper;
import org.apache.ibatis.annotations.Insert;
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
public class DeptController {

    @Autowired             //注入DepartmentMapper 
    DepartmentMapper departmentMapper;

    @GetMapping("/dept/{id}")     //处理映射（发送请求）{id}以占位符的形式取出id，@PathVariable路径变量
    public Department getDepartment(@PathVariable("id") Integer id){
        return departmentMapper.getDeptById(id);
    }

    @GetMapping("/dept")
    public Department insertDept(Department department){
        departmentMapper.insertDept(department);
        return department;
    }
}

查询第一个人的信息：http://localhost:8080/dept/1

插入数据http://localhost:8080/dept?departmentName=FF

数据库信息增加

问题：如果将数据库表的列名改为department_name原来为departmentName此时departmentName不能被数据库封装，此时还要开启驼峰命名法（不写配置文件的写法）写一个配置类MyBatisConfig自定义MyBatis的配置规则
MyBatisConfig.class作用：开启驼峰命名法

package com.atorg.springboot.config;

import org.apache.ibatis.session.Configuration;
import org.mybatis.spring.boot.autoconfigure.ConfigurationCustomizer;
import org.springframework.context.annotation.Bean;

@org.springframework.context.annotation.Configuration
public class MyBatisConfig {

    @Bean
    public ConfigurationCustomizer configurationCustomizer(){
         return new ConfigurationCustomizer(){

            @Override
            public void customize(Configuration configuration) {
                configuration.setMapUnderscoreToCamelCase(true);
            }
        };
    }
}

6.使用MyBatis对数据库进行增删改查（MyBatis配置文件版）

1.编写EmployeeMapper接口

package com.atorg.springboot.mapper;

import com.atorg.springboot.bean.Employee;
//@Mapper或者@MapperScan将接口扫描到容器中
public interface EmployeeMapper {
    //查询员工
    public Employee getEmpById(Integer id);
    //插入员工
    public void insertEmp(Employee employee);
}

2.配置全局配置文件

全局配置文件参考
mybatis-config.xml

<?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>           //开启驼峰命名法
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
</configuration>

sql映射文件参考
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.atorg.springboot.mapper.EmployeeMapper">//跟EmployeeMapper接口进行绑定
<!-- public Employee getEmpByTd(Integer id);
    public void insertEmp(Employee employee);-->
    //配置文件形式查询数据
    <select id="getEmpById" resultType="com.atorg.springboot.bean.Employee">//resultType指明返回值类型
        SELECT * FROM employee WHERE id=#{id}
    </select>
    //配置文件形式插入数据
    <insert id="insertEmp">
        INSERT INTO employee(lastName,email,gender,d_id) VALUES (#{lastName},#{email},#{gender},#{dId})
    </insert>
</mapper>

要让MyBatis知道mybatis的全局配置文件以及sql映射文件存在并且起作用我们要在yml中指明MyBatis全局配置文件以及sql映射文件Mapper的位置
配置文件版的核心步骤

mybatis:
  config-location: classpath:mybatis/mybatis-config.xml    #mybatis全局配置文件的位置
  mapper-locations: classpath:mybatis/mapper/*.xml       #sql映射文件的位置

3.编写Controller进行测试

@Autowired//注入EmployeeMapper
EmployeeMapper employeeMapper;

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

启动应用运行截图