Spring Boot 教程(2) - Mybatis

2020-05-19 16:15:45来源：博客园阅读 ()

Spring Boot 教程(2) - Mybatis

Spring Boot 教程 - Mybatis

1. 什么是Mybatis?

MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

2. Spring Boot 整合 Mybatis

2.1 引入maven坐标

<!--springboot父工程-->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <dependencies>
        <!--springboot框架web组件-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.2.2.RELEASE</version>
        </dependency>
        <!--mybatis整合springboot组件-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.0</version>
        </dependency>
        <!--mysql数据库连接驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.18</version>
        </dependency>
        <!--lombok组件-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.10</version>
        </dependency>
    </dependencies>

    <build>
        <!--springboot的maven插件-->
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <compilerArgs>
                        <arg>-parameters</arg>
                    </compilerArgs>
                </configuration>
            </plugin>
        </plugins>
    </build>

2.2 编写代码

2.2.1 创建如图所示的目录结构

记得两个mapper文件的路径要一致，在编译之后mybatis的映射文件和接口文件才会在同一个目录下。

2.2.2 代码编写

2.2.2.1 创建配置文件和启动类

application.yml：

butterflytri:
  databaseurl-port: 127.0.0.1:3306 # 数据库端口
  database-name: student_db # 数据库名
server:
  port: 8080 # 应用端口
  servlet:
    context-path: /butterflytri # 应用映射
spring:
  application:
    name: mybatis # 应用名称
  datasource:
    url: jdbc:mysql://${butterflytri.databaseurl-port}/${butterflytri.database-name}?useUnicode=true&characterEncoding=UTF-8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: root
mybatis:
  type-aliases-package: org.wjf.entity # entity别名
  mapper-locations: classpath:org/wjf/mapper/*Mapper.xml # mapper映射包扫描

启动类MybatisApplication.java：

package org.butterflytri;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * @author: WJF
 * @date: 2020/5/16
 * @description: MybatisApplication
 */
@SpringBootApplication
public class MybatisApplication {

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

}

2.2.2.2 创建实体类Student

在entity包下创建Student.java实体类。

package org.butterflytri.entity;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

import java.io.Serializable;

/**
 * @author: WJF
 * @date: 2020/5/16
 * @description: Student
 */

@ToString
@Getter
@Setter
public class Student implements Serializable {

    private Long id;

    private String studentName;

    private String studentNo;

    private String sex;

    private Integer age;

}

2.2.2.3 编写mybatis接口文件

在mapper包下创建StudentMapper.java接口。

package org.butterflytri.mapper;

import org.apache.ibatis.annotations.Mapper;
import org.butterflytri.entity.Student;

import java.util.List;

/**
 * @author: WJF
 * @date: 2020/5/16
 * @description:
 */
@Mapper
public interface StudentMapper {

    /**
     * 查询所有学生信息
     * @return List<Student>
     */
    List<Student> findAll();

    /**
     * 通过id查询学生信息
     * @param id
     * @return Student
     */
    Student findOne(Long id);

    /**
     * 通过学号查询学生信息
     * @param studentNo
     * @return Student
     */
    Student findByStudentNo(String studentNo);

}

2.2.2.4 创建mybatis映射文件

在mapper包下创建StudentMapper.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="org.butterflytri.mapper.StudentMapper">
    <sql id="propertyMapper">
        `ID` AS id,
        `STUDENT_NAME` AS studentName,
        `STUDENT_NO` AS studentNo,
        `SEX` AS sex,
        `AGE` AS age
    </sql>
    <select id="findAll" resultType="org.butterflytri.entity.Student">
        SELECT
            <include refid="propertyMapper"></include>
        FROM
            `t_student`
    </select>
    <select id="findOne" parameterType="java.lang.Long" resultType="org.butterflytri.entity.Student">
        SELECT
            <include refid="propertyMapper"></include>
        FROM
            `t_student`
        WHERE
            `ID` = #{id}
    </select>
    <select id="findByStudentNo" parameterType="java.lang.String" resultType="org.butterflytri.entity.Student">
        SELECT
            <include refid="propertyMapper"></include>
        FROM
            `t_student`
        WHERE
            `STUDENT_NO` = #{studentNo}
    </select>
</mapper>

2.2.2.5 Service层

在service包下创建StudentService.java接口，在impl包下创建StudentServiceImpl.Java类并继承StudentService.Java接口。

StudentService.java：

package org.butterflytri.service;

import org.butterflytri.entity.Student;

import java.util.List;

/**
 * @author: WJF
 * @date: 2020/5/16
 * @description: StudentService
 */

public interface StudentService {

    public List<Student> findAll();

    public Student findOne(Long id);

    public Student findByStudentNo(String studentNo);
}

StudentServiceImpl.java：

package org.butterflytri.service.impl;

import org.butterflytri.entity.Student;
import org.butterflytri.mapper.StudentMapper;
import org.butterflytri.service.StudentService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

/**
 * @author: WJF
 * @date: 2020/5/16
 * @description: StudentServiceImpl
 */
@Service
public class StudentServiceImpl implements StudentService {

    @Resource
    private StudentMapper studentMapper;

    @Override
    public List<Student> findAll() {
        return studentMapper.findAll();
    }

    @Override
    public Student findOne(Long id) {
        return studentMapper.findOne(id);
    }

    @Override
    public Student findByStudentNo(String studentNo) {
        return studentMapper.findByStudentNo(studentNo);
    }
}

2.2.2.6 Controller层

在controller包下创建StudentController.java控制器类。

package org.butterflytri.controller;

import org.butterflytri.entity.Student;
import org.butterflytri.service.StudentService;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import java.util.List;

/**
 * @author: WJF
 * @date: 2020/5/16
 * @description: StudentController
 */
@RestController
@RequestMapping("/student")
public class StudentController {

    @Resource
    private StudentService studentService;

    @RequestMapping("/findAll")
    public List<Student> findAll() {
        return studentService.findAll();
    }

    @RequestMapping("/findOne")
    public Student findOne(Long id) {
        return studentService.findOne(id);
    }

    @RequestMapping("/findByStudentNo")
    public Student findByStudentNo(String studentNo) {
        return studentService.findByStudentNo(studentNo);
    }

}