创建项目

使用Intellj IDEA创建SpringBoot项目，其中Server URL可以使用阿里云的URL，地址为https://start.aliyun.com/，填写完毕后点击Next

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选择3.0以下的SpringBoot版本，并引入SpringWeb依赖，点击Create创建项目

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配置

导入坐标

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<dependency><!-- mysql  驱动-->
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.26</version>
</dependency>

<dependency><!-- lombok  ,自动生成get,Set 方法-->
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

<dependency><!--mybatisplus起步依赖-->
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.4.0</version>
</dependency>

<dependency><!--boot整合mybatis所需要的包，为了使用xml映射文件-->
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.2.2</version>
</dependency>

数据源

在application.yml文件中写入以下内容：

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# 应用服务 WEB 访问端口
server:
  port: 8080
spring:
  datasource:
    url: jdbc:mysql://127.0.0.1:3307/itheima?useSSL=false
    username: manager
    password: mk123456
    driver-class-name: com.mysql.jdbc.Driver

# MyBatisPlus相关配置
mybatis-plus:
  global-config:
    db-config:
      # 表名前缀
      table-prefix: tb_
      # id生成策略 数据库自增
      id-type: auto
  configuration:
  	# 下划线转驼峰
    map-underscore-to-camel-case: true
    # 日志
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
    
# MyBatis相关配置
mybatis:
  # 告诉mybatis对应的实体类位置
  type-aliases-package: com.example.springbootmybatisplus.entity
  # 告诉mybatisSQL的映射文件在这里
  mapper-locations: classpath*:mapper/*.xml

建表

执行下面的sql脚本，创建测试用的表

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drop table if exists tb_user;

create table tb_user(
	id int primary key auto_increment,
	username varchar(20),
	password varchar(20),
	gender char(1),
	addr varchar(30)
);

INSERT INTO tb_user VALUES (1, 'zhangsan', '123', '男', '北京');
INSERT INTO tb_user VALUES (2, '李四', '234', '女', '天津');
INSERT INTO tb_user VALUES (3, '王五', '11', '男', '西安');

实体类

新建实体类com.example.springbootmybatisplus.entity.User

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package com.example.springbootmybatisplus.entity;

import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

@Data
@TableName("tb_user")
public class User {
    @TableId()
    private Integer id;
    private String username;
    private String password;
    private Character gender;
    private String addr;
}

映射

注解映射

新建Mapper接口com.example.springbootmybatisplus.mapper.UserMapper

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package com.example.springbootmybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.springbootmybatisplus.entity.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserMapper extends BaseMapper<User> {
}

XML映射

在src/resources/mapper下创建UserMapper.xml文件，模板如下

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<?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.springbootmybatisplus.mapper.UserMapper">

</mapper>

配置扫描

在启动类加上@MapperScan({"com.example.springbootmybatisplus.mapper"})以配置Mapper扫描

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@SpringBootApplication
@MapperScan({"com.example.springbootmybatisplus.mapper"})
public class SpringbootmybatisplusApplication {

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

}

服务类

新建Service接口com.example.springbootmybatisplus.service.UserService

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package com.example.springbootmybatisplus.service;

import com.example.springbootmybatisplus.entity.User;
import com.baomidou.mybatisplus.extension.service.IService;

public interface UserService extends IService<User> {
}

新建Service实现类com.example.springbootmybatisplus.service.impl.UserServiceImpl

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package com.example.springbootmybatisplus.service.impl;

import com.example.springbootmybatisplus.entity.User;
import com.example.springbootmybatisplus.mapper.UserMapper;
import com.example.springbootmybatisplus.service.UserService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
}

控制器

新建Controller控制器com.example.springbootmybatisplus.controller.UserController

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package com.example.springbootmybatisplus.controller;

import com.example.springbootmybatisplus.entity.User;
import com.example.springbootmybatisplus.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;

    @GetMapping
    public List<User> findAll() {
        return userService.list();
    }
}

测试

运行启动类，使用浏览器访问http://localhost:8080/user，返回值如下：

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[
    {
        id: 1,
		username: "zhangsan",
		password: "123",
		gender: "男",
		addr: "北京"
    },
    {
        id: 2,
		username: "李四",
		password: "234",
		gender: "女",
		addr: "天津"
    },
    {
        id: 3,
		username: "王五",
		password: "11",
		gender: "男",
		addr: "西安"
    }
]