SpringBoot整合Mybatis完整详细版

转载自：https://blog.csdn.net/iku5200/article/details/82856621

IDE：idea、DB：mysql

新建一个Spring Initializr项目

创建项目的文件结构以及jdk的版本

选择项目所需要的依赖
修改项目名，finish完成
来看下建好后的pom.xml

<?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>
 
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
 
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
 
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
 
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
 
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>
 
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <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>

修改配置文件
本文不使用application.properties文件而使用更加简洁的application.yml文件。将resource文件夹下原有的application.properties文件删除，创建application.yml配置文件（备注：其实SpringBoot底层会把application.yml文件解析为application.properties），本文创建了两个yml文件（application.yml和application-dev.yml），分别来看一下内容

application.yml

spring:
  profiles:
    active: dev

application-dev.yml

server:
  port: 8080
 
spring:
  datasource:
    username: root
    password: ok123
    url: jdbc:mysql://localhost:3306/springboot?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=UTC
    driver-class-name: com.mysql.jdbc.Driver
 
mybatis:
  mapper-locations: classpath:mapper/*Mapper.xml
  type-aliases-package: com.example.entity
 
#showSql
logging:
  level:
    com:
      example:
        mapper : debug

两个文件的意思是：

在项目中配置多套环境的配置方法。
因为现在一个项目有好多环境，开发环境，测试环境，准生产环境，生产环境，每个环境的参数不同，所以我们就可以把每个环境的参数配置到yml文件中，这样在想用哪个环境的时候只需要在主配置文件中将用的配置文件写上就行如application.yml

笔记：在Spring Boot中多环境配置文件名需要满足application-{profile}.yml的格式，其中{profile}对应你的环境标识，比如：
application-dev.yml：开发环境
application-test.yml：测试环境
application-prod.yml：生产环境
至于哪个具体的配置文件会被加载，需要在application.yml文件中通过spring.profiles.active属性来设置，其值对应{profile}值。

还有配置文件中最好不要有中文注释，会报错。

接下来把启动文件移到com.example下，而且springboot的启动类不能放在java目录下！！！必须要个包将它包进去

否则会报错误：

Your ApplicationContext is unlikely to start due to a @ComponentScan of the default package.

这个原因值得注意就是因为有时候很难在IDEA中的项目目录认出来这个错误并且还容易扫描不到一些类

正确写法，启动类没有直接放在java目录下

错误写法，启动类直接放在java目录下

然后开始创建实体类实现业务流程
创建包controller、entity、mapper、service。resources下创建mapper文件夹，用于写sql语句，也可以用注解的方式直接写在mapper文件里。下面直接贴代码

数据库表结构

CREATE TABLE `t_user` (
  'id' int(32) NOT NULL AUTO_INCREMENT,
  'userName' varchar(32) NOT NULL,
  'passWord' varchar(50) NOT NULL,
  'realName' varchar(32) DEFAULT NULL,
  PRIMARY KEY ('id')
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

用户表

entity.java

package com.example.entity;
 
public class User {
    private Integer id;
    private String userName;
    private String passWord;
    private String realName;
 
    public Integer getId() {
        return id;
    }
 
    public void setId(Integer id) {
        this.id = id;
    }
 
    public String getUserName() {
        return userName;
    }
 
    public void setUserName(String userName) {
        this.userName = userName;
    }
 
    public String getPassWord() {
        return passWord;
    }
 
    public void setPassWord(String passWord) {
        this.passWord = passWord;
    }
 
    public String getRealName() {
        return realName;
    }
 
    public void setRealName(String realName) {
        this.realName = realName;
    }
 
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", passWord='" + passWord + '\'' +
                ", realName='" + realName + '\'' +
                '}';
    }
}

UserMapper.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.example.mapper.UserMapper">
    <select id="selectUserById" parameterType="int" resultType="User">
        SELECT * FROM t_user WHERE id = #{id}
    </select>
</mapper>

UserMapper.java

package com.example.mapper;

import com.example.entity.User;
import org.springframework.stereotype.Repository;

@Repository
public interface UserMapper {

    public User selectUserById(int id);
}

UserService.java

package com.example.service;

import com.example.entity.User;

public interface UserService {

    public User selectUserById(int id);
}

UserServiceImpl.java

package com.example.service.Impl;

import com.example.entity.User;
import com.example.mapper.UserMapper;
import com.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;


@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

    @Override
    public User selectUserById(int id) {
        return userMapper.selectUserById(id);
    }
}

UserController.java

package com.example.controller;

import com.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @Autowired
    private UserService userService;

    @RequestMapping("/getUser/{id}")
    public String getUser(@PathVariable("id") int id){
        return userService.selectUserById(id).toString();
    }
}

完成以上，下面在启动类里加上注解用于给出需要扫描的mapper文件路径@MapperScan("com.example.mapper")

package com.example;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@MapperScan("com.example.mapper")  //扫描 mapper接口
@SpringBootApplication
public class SpringbootMybatisApplication {

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

}

最后启动，浏览器输入地址看看吧：http://localhost:8080/getUser/3

测试成功，就这样基本框架就搭建成功了