整体项目结构

pom.xml 配置

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.5.5</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.study</groupId>
	<artifactId>mybatis-plus</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>mybatis-plus</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>com.baomidou</groupId>
			<artifactId>mybatis-plus-boot-starter</artifactId>
			<version>3.4.3.4</version>
		</dependency>

	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<configuration>
					<excludes>
						<exclude>
							<groupId>org.projectlombok</groupId>
							<artifactId>lombok</artifactId>
						</exclude>
					</excludes>
				</configuration>
			</plugin>
		</plugins>
		<resources>
			<resource>
				<directory>src/main/java</directory><!--所在的目录-->
				<includes>
					<include>**/*.xml</include>
				</includes>
				<filtering>false</filtering>
			</resource>
		</resources>
	</build>
</project>

application.properties

server.port = 8044
spring.datasource.url=jdbc:h2:mem:test_db;DATABASE_TO_UPPER=false;MODE=MYSQL;DB_CLOSE_ON_EXIT=FALSE;
spring.h2.console.enabled=true
spring.datasource.driver-class-name=org.h2.Driver
#maper.xml路径
mybatis-plus.mapper-locations=classpath:com/study/mybatisplus/dao/mapper/**.xml
#sql 打印在控制台
logging.level.com.study.mybatisplus.dao=debug

主启动类

@SpringBootApplication
@MapperScan("com.study.mybatisplus.dao")
public class MybatisPlusApplication {
	public static void main(String[] args) {
		SpringApplication.run(MybatisPlusApplication.class, args);
	}
}

分页配置

import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import javafx.scene.control.Pagination;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MybatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor(){
        MybatisPlusInterceptor  interceptor = new MybatisPlusInterceptor ();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

controller层

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.study.mybatisplus.dao.UserDao;
import com.study.mybatisplus.po.User;
import com.study.mybatisplus.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;
import java.util.stream.Collectors;

@RestController
public class UserController {

    @Autowired
    private UserService userService;
    @Autowired
    private UserDao userDao;

    @PostMapping("/add")
    public int add(@RequestBody User user) {
        int user1 = userService.createUser(user);
        return user1;
    }

    @GetMapping("/list")
    public List<User> list() {
        List<User> users = userDao.selectList(null);
        List<User> collect = users.stream().filter(x -> x.getId() > 11).collect(Collectors.toList());
        collect.forEach(System.out::println);
        return collect;
    }
    @GetMapping("/findList")
    public IPage<User> findList() {
        IPage<User> list = userService.findList();

        return list;
    }
    @GetMapping("/getById")
    public User getById(Long id) {
        User users = userDao.getStudentById(id);

        return users;
    }
}

service

public interface UserService extends IService<User> {
    int createUser(User user);
    IPage<User> findList();
}

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.study.mybatisplus.dao.UserDao;
import com.study.mybatisplus.po.User;
import com.study.mybatisplus.service.UserService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;

@Service
public class UserServiceImpl extends ServiceImpl<UserDao,User> implements UserService {
    @Resource
    private UserDao userDao;

    @Override
    public int createUser(User user) {
       return userDao.insert(user);
    }

    @Override
    public IPage<User> findList() {
        IPage<User> page= new Page(1,2);
        IPage<User>  users = userDao.findList(page);
        return users;
    }
}

dao

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.study.mybatisplus.po.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface UserDao extends BaseMapper<User>  {

    User getStudentById(Long id);
    IPage<User>  findList(IPage<User> page);
}

<?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.study.mybatisplus.dao.UserDao">

    <resultMap id="userMap" type="com.study.mybatisplus.po.User">
        <id property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="age" column="age"/>
    </resultMap>
    <select id="getStudentById" parameterType="long" resultType="com.study.mybatisplus.po.User">
        select *
        from user
        <where>
            <if test="id != null and id !=''">
                id=#{id}
            </if>
        </where>
    </select>
    <select id="findList"  resultType="com.study.mybatisplus.po.User">
        select *
        from user
    </select>
</mapper>

po

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

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Data
@Entity
@TableName("user")
public class User {
    @Id
    private Long id;
    private String name;
    private Integer age;
}