【SpringBoot】15 数据访问P3 整合Mybatis

重新建立一个SpringBoot工程

选择依赖组件

然后删除不需要的Maven&Git文件

还是先查看我们的POM文件

整合Mybatis的组件多了这一个，默认的版本是3.5.4

然后再看看整个Mybatis整合的体系

创建数据库信息：

部门表：

CREATE TABLE `t_department` (
  `id` int unsigned NOT NULL AUTO_INCREMENT,
  `department_name` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8

职员表

CREATE TABLE `t_employee` (
  `id` int unsigned NOT NULL AUTO_INCREMENT,
  `last_name` varchar(10) DEFAULT NULL,
  `email` varchar(50) DEFAULT NULL,
  `gender` int DEFAULT NULL,
  `department_id` int unsigned NOT NULL,
  PRIMARY KEY (`id`),
  KEY `fk_emp_dp_dpid` (`department_id`),
  CONSTRAINT `fk_emp_dp_dpid` FOREIGN KEY (`department_id`) REFERENCES `t_department` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8

添加外键关联：【每次都会不可绑定，因为一些约束没有一致，要仔细找找】

ALTER TABLE table_name 
ADD CONSTRAINT fk_table1_table2
FOREIGN KEY (column_name) 
REFERENCES table2(column_name);

然后编写我们的数据源配置信息【用的默认Hikari】

spring:
  datasource:
    type: com.zaxxer.hikari.HikariDataSource
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql:///mybatis?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8
    username: root
    password: 123456

编写ORM实体类

部门类

package cn.dai.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.apache.ibatis.type.Alias;

/**
 * @author ArkD42
 * @file SpringBoot with Mybatis
 * @create 2020 - 05 - 31 - 22:43
 */

@Alias("department")
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Department {

    private Integer id;
    private String department_name;
}

然后是职员类

package cn.dai.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.apache.ibatis.type.Alias;

/**
 * @author ArkD42
 * @file SpringBoot with Mybatis
 * @create 2020 - 05 - 31 - 22:40
 */

@Alias("employee")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Employee {

    private Integer id;
    private String last_name;
    private String email;
    private Integer gender;
    private Integer department_id;

}

1、【使用全注解完成映射配置】

编写映射接口

package cn.dai.mapper;

import cn.dai.pojo.Department;
import org.apache.ibatis.annotations.*;

import java.util.List;

/**
 * @author ArkD42
 * @file SpringBoot with Mybatis
 * @create 2020 - 05 - 31 - 22:46
 */

@Mapper //指定这是映射接口
public interface DepartmentMapper {

    @Select("SELECT * FROM t_department")
    List<Department> getAllDepartments();

    @Select("SELECT * FROM t_department WHERE id = #{dp_id}")
    Department getDepartmentById(@Param("dp_id") Integer id);

    @Delete("DELETE FROM t_department WHERE id = #{dp_id}")
    int deleteDepartmentById(@Param("dp_id")Integer id);

    @Insert("INSERT INTO t_department(department_name) VALUES(#{name})")
    int addDepartment(@Param("name") String department_name);

    @Update("UPDATE t_department SET department_name = #{department_name} WHERE id = #{id}")
    int updateDepartmentById(Department department);

}

测试使用的部门控制器，通过地址参数进行SQL测试

package cn.dai.controller;

import cn.dai.mapper.DepartmentMapper;
import cn.dai.pojo.Department;
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;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.List;

/**
 * @author ArkD42
 * @file SpringBoot with Mybatis
 * @create 2020 - 05 - 31 - 23:02
 */

@RestController
public class DepartmentController {

    @Autowired
    DepartmentMapper departmentMapper;

    @GetMapping("/department/get_by_id/{id}")
    public Department getDepartmentById(@PathVariable("id") Integer id){
        return departmentMapper.getDepartmentById(id);
    }

    @GetMapping("/department/listAll")
    public List<Department> getAllDepartments(){
        return departmentMapper.getAllDepartments();
    }

    @GetMapping("/department/del_by_id/{id}")
    public String deleteDepartmentById(@PathVariable("id")Integer id){
        return "删除结果：" + departmentMapper.deleteDepartmentById(id);
    }

    @GetMapping("/department/update_by_id/{dept}")
    public String updateDepartmentById(@PathVariable("dept")Department department){
        return "更新结果：" + departmentMapper.updateDepartmentById(department);
    }

    @GetMapping("/department/add/{dept_name}")
    public String addDepartment(@PathVariable("dept_name")String name) throws UnsupportedEncodingException {
        String decode = URLDecoder.decode(name, "utf-8");
        return "添加结果：" + departmentMapper.addDepartment(decode);
    }

}

不过这里要注意的一点是这个自动装配会爆红警告，说无法装配，因为没有注册这个部门映射接口Bean类型

直接无视测试运行

测试结果

查询所有部门

按ID查询部门

然后是这个通过名字查询出现了BUG

因为地址栏解析会变成URL字符，这里要变换成UTF8注入才行

然后更改为URL解码即可

    @GetMapping("/department/add/{dept_name}")
    public String addDepartment(@PathVariable("dept_name")String name) throws UnsupportedEncodingException {
        String decode = URLDecoder.decode(name, "utf-8");
        return "添加结果：" + departmentMapper.addDepartment(decode);
    }

在原生Mybatis的时候一切设置交给Mybatis核心配置文件设置xml标签完成

如果整合的是Spring容器，则通过SQL会话工厂Bean注入配置完成

现在在SpringBoot中，我们通过自定义配置类来实现这个功能

package cn.dai.config;

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

/**
 * @author ArkD42
 * @file SpringBoot with Mybatis
 * @create 2020 - 06 - 01 - 11:23
 */
//自定义Mybatis配置规则
@org.springframework.context.annotation.Configuration
public class MybatisConfig {
    
    @Bean
    public ConfigurationCustomizer configurationCustomizer(){

        return new ConfigurationCustomizer(){
            
            @Override
            public void customize(Configuration configuration) {
                
                // 开启驼峰命名，如果这里的ORM和表字段一样，不要开启
                //configuration.setMapUnderscoreToCamelCase(true);
            }
        };
    }
}

另外，如果映射接口数量众多，不可能每一个接口都要这样打注解Mapper

所以我们需要这样一个注解@MapperScan打在启动Main类

在Main入口类中

注意和MapperScans区分开来，这个是没有S的

2、【使用配置文件完成映射配置】

Mybatis的配置文件包括核心配置文件和映射配置

我们先来编写映射接口

package cn.dai.mapper;

import cn.dai.pojo.Employee;

import java.util.List;

/**
 * @author ArkD42
 * @file SpringBoot with Mybatis
 * @create 2020 - 06 - 01 - 11:35
 */

public interface EmployeeMapper {

    List<Employee> getAllEmployees();

    Employee getEmployeeById();

    int addEmployee(Employee employee);

    int deleteEmployeeById(Integer id);

    int updateEmployeeById(Employee employee);
}

这里不用注解则采用原生Mybatis映射器配置【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.dai.mapper.EmployeeMapper">
<!--
    List<Employee> getAllEmployees();

    Employee getEmployeeById();

    int addEmployee(Employee employee);

    int deleteEmployeeById(Integer id);

    int updateEmployeeById(Employee employee);
-->

    <select id="getAllEmployees" resultType="cn.dai.pojo.Employee">
        SELECT * FROM t_employee
    </select>

    <select id="getEmployeeById" resultType="cn.dai.pojo.Employee">
        SELECT * FROM t_employee WHERE id = #{emp_id}
    </select>


    <insert id="addEmployee" parameterType="cn.dai.pojo.Employee">
        INSERT INTO t_employee(last_name,email,gender,department_id)
        VALUES(#{last_name},#{email},#{gender},#{department_id})
    </insert>

    <delete id="deleteEmployeeById" parameterType="int">
        DELETE FROM t_employee WHERE id = #{id}
    </delete>

    <update id="updateEmployeeById" parameterType="int">
        UPDATE
            t_employee
        SET
            last_name = #{last_name},
            email = #{email},
            gender = #{gender},
            department_id = #{department_id}
        WHERE
            id = #{id}
    </update>

</mapper>

要让SpringBoot加载原生Mybatis的XML配置，就必须在配置信息中加入这些东西

mybatis:
  config-location: classpath:mybatis/mybatis-config.xml
  mapper-locations: classpath:mybatis/mapper/*.xml

这里还忘了核心XML配置，补上

【注意这个核心配置文件，不需要写映射器注册，这个工作在SpringBoot配置信息里设置】

【否则重复注册会导致SpringBoot启动异常，说找不到这个Bean，然后结尾是导入注册异常】

<?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>

配置文件位置

在SpringBoot中配置Mybatis配置文件的信息

mybatis:
  config-location: classpath:mybatis/mybatis-config.xml
  mapper-locations: classpath:mybatis/mapper/*.xml

然后编写员工表测试控制器类

package cn.dai.controller;

import cn.dai.mapper.EmployeeMapper;
import cn.dai.pojo.Employee;
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.PostMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @author ArkD42
 * @file SpringBoot with Mybatis
 * @create 2020 - 06 - 01 - 13:28
 */

@RestController
public class EmployeeController {

    @Autowired
    EmployeeMapper employeeMapper;

    @GetMapping("/employee/listAll")
    public List<Employee> getAllEmployees(){
        return employeeMapper.getAllEmployees();
    }

    @GetMapping("/employee/get_by_id/{emp_id}")
    public Employee getEmployeeById(@PathVariable("emp_id") Integer id){
        return employeeMapper.getEmployeeById();
    }

    @PostMapping("/employee/add")
    public String addEmployee(Employee employee){
        return "添加结果：" + employeeMapper.addEmployee(employee);
    }

    @GetMapping("/employee/del_by_id/{emp_id}")
    public String deleteEmployeeById(@PathVariable("emp_id") Integer id){
        return "删除结果：" + employeeMapper.deleteEmployeeById(id);
    }

    @PostMapping("/employee/upd_by_id/")
    public String updateEmployeeById(Employee employee){
        return "修改结果：" + employeeMapper.updateEmployeeById(employee);
    }

}

测试结果

关于Mybatis的一些Dao设置也可以在核心配置中设置

总结：

一定要注意跟映射接口相关的映射器配置，不要重复性注册映射器

遇上找不到的异常错误，一般都出现在这个问题上面，仔细留意

【另外跟重复设置有关的还有日志输出，等等，都是因为重复配置导致的问题】