SpringBoot系列—1.IDEA搭建SpringBoot框架
SpringBoot系列—2.SpringBoot拦截器篇
SpringBoot系列—3.SpringBoot Redis篇
SpringBoot系列—4.SpringBoot 整合Mybatis、MP（MyBatis-Plus）
SpringBoot系列—5.SpringBoot 整合Mybatis-Plus分页

**1.pom.xml引入依赖（mybatis、mysql-connect、mp）

<!-- mybatis -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.1</version>
</dependency>

<!-- mysql-connector -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

<!-- mybatis-plus -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.3.1.tmp</version>
</dependency>

<!-- mybatis-plus代码生成器 -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-generator</artifactId>
    <version>3.3.1.tmp</version>
</dependency>

<!-- freemarker模板 -->
<dependency>
    <groupId>org.freemarker</groupId>
    <artifactId>freemarker</artifactId>
    <version>2.3.29</version>
</dependency>

2.mysql创建数据库，创建一个user表

3.配置数据库连接

# 驱动配置信息
spring.datasource.driverClassName=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/demo?characterEncoding=UTF-8&useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.username=root
spring.datasource.password=12345678
# mybatis扫描包
mybatis.type-aliases-package=com.example.demo.entity
mybatis.mapper-locations=classpath:mybatis/mapper/*.xml
mybatis-plus.type-aliases-package=com.example.demo.entity
mybatis-plus.mapper-locations=classpath:mybatis/mapper/*.xml

4.新建MPCodeGeneratorHelper类，使用mybatis-plus-generator进行代码生成

package com.example.demo.helper;

import com.baomidou.mybatisplus.core.toolkit.StringPool;
import com.baomidou.mybatisplus.generator.AutoGenerator;
import com.baomidou.mybatisplus.generator.InjectionConfig;
import com.baomidou.mybatisplus.generator.config.*;
import com.baomidou.mybatisplus.generator.config.po.TableInfo;
import com.baomidou.mybatisplus.generator.config.rules.NamingStrategy;
import com.baomidou.mybatisplus.generator.engine.FreemarkerTemplateEngine;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PropertiesLoaderUtils;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

/**
 * 代码生成器配置
 */
public class MPCodeGeneratorHelper {
    //  数据库连接url
    private static String dbUrl;
    // 数据库驱动
    private static String dbDriverName;
    //数据库连接名称
    private static String dbUserName;
    //数据库连接密码
    private static String dbPassword;

    public static void main(String[] args) {
        // 加载DB配置信息
        loadDbProperty();
        // 代码生成器
        AutoGenerator mpg = new AutoGenerator();
        // 全局配置
        GlobalConfig gc = new GlobalConfig();
        String projectPath = System.getProperty("user.dir");
        gc.setOutputDir(projectPath + "/src/main/java");
        gc.setAuthor("Kevin");
        gc.setOpen(false);
        mpg.setGlobalConfig(gc);

        // 数据源配置
        DataSourceConfig dsc = new DataSourceConfig();
        dsc.setUrl(dbUrl);
        dsc.setDriverName(dbDriverName);
        dsc.setUsername(dbUserName);
        dsc.setPassword(dbPassword);
        mpg.setDataSource(dsc);

        // 包配置
        PackageConfig pc = new PackageConfig();
        pc.setParent("com.example.demo");
        mpg.setPackageInfo(pc);

        // 自定义配置
        InjectionConfig cfg = new InjectionConfig() {
            @Override
            public void initMap() {
            }
        };
        // 自定义输出配置
        List<FileOutConfig> focList = new ArrayList<>();
        // 自定义配置会被优先输出
        focList.add(new FileOutConfig("/templates/mapper.xml.ftl") {
            @Override
            public String outputFile(TableInfo tableInfo) {
                return projectPath + "/src/main/resources/mybatis/mapper/" + tableInfo.getEntityName() + "Mapper" + StringPool.DOT_XML;
            }
        });
        cfg.setFileOutConfigList(focList);
        mpg.setCfg(cfg);
        // 配置模板
        TemplateConfig templateConfig = new TemplateConfig();
        templateConfig.setXml(null);
        mpg.setTemplate(templateConfig);
        // 策略配置
        StrategyConfig strategy = new StrategyConfig();
        strategy.setNaming(NamingStrategy.underline_to_camel);
        strategy.setColumnNaming(NamingStrategy.underline_to_camel);
        strategy.setEntityLombokModel(false);
        strategy.setRestControllerStyle(true);
        strategy.setControllerMappingHyphenStyle(true);
        strategy.setTablePrefix(pc.getModuleName() + "_");
        mpg.setStrategy(strategy);
        mpg.setTemplateEngine(new FreemarkerTemplateEngine());
        mpg.execute();
    }

    /**
     * 加载数据量属性配置信息
     */
    private static void loadDbProperty(){
        Properties props = null;
        try {
            Resource resource = new ClassPathResource("/application.properties");//
            props = PropertiesLoaderUtils.loadProperties(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        dbUrl = props.getProperty("spring.datasource.url","");
        dbDriverName = props.getProperty("spring.datasource.driverClassName","");
        dbUserName = props.getProperty("spring.datasource.username","");
        dbPassword = props.getProperty("spring.datasource.password","");
    }
}

5.主类新增Mapper扫描注解@MapperScan("com.example.demo.mapper")

package com.example.demo;

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

@SpringBootApplication
@MapperScan("com.example.demo.mapper")
public class DemoApplication {

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

}

6.右键MPCodeGeneratorHelper，Run ‘MPCodeGeneratorHelper.main()’，系统会自动生成entity、controller、mapper、service

7.使用mybatis-plus进行增删改查
1）编写UserController.java （如果userMapper出现：Could not autowire. No beans of 'UserMapper' type found.
解决办法：在UserMapper.java添加类注解@Repository即可）

package com.example.demo.controller;

import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

/**
 * <p>
 *  前端控制器
 * </p>
 *
 * @author Kevin
 * @since 2020-02-05
 */
@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserMapper userMapper;

    /**
     * 增
     * @return
     */
    @RequestMapping("/add")
    @ResponseBody
    private String add(){
        User user = new User();
        user.setName("Kevin");
        user.setAge(24);
        user.setSex("男");
        int result = userMapper.insert(user);
        return result==0?"数据新增失败":"数据新增成功";
    }

    @RequestMapping("/delete")
    @ResponseBody
    private String delete(){
        return userMapper.deleteById(1)==0?"数据删除失败":"数据删除成功";
    }

    @RequestMapping("/update")
    @ResponseBody
    private String update(){
        User user = userMapper.selectById(1);
        user.setName("Tony");
        return userMapper.updateById(user)==0?"数据更新失败":"数据更新成功";
    }

    @RequestMapping("/query")
    @ResponseBody
    private String query(){
        return userMapper.selectList(null).toString();
    }
}

2）为防止请求返回的中文出现乱码，新增字符集拦截器设置UTF-8即可

package com.example.demo.interceptor;

import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;

import java.nio.charset.StandardCharsets;
import java.util.List;

@Configuration
public class InterceptorConfig extends WebMvcConfigurationSupport {

    @Override
    protected void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        // 解决controller返回字符串中文乱码问题
        for (HttpMessageConverter<?> converter : converters) {
            if (converter instanceof StringHttpMessageConverter) {
                ((StringHttpMessageConverter)converter).setDefaultCharset(StandardCharsets.UTF_8);
            }
        }
    }
}

3）测试mybatis-plus是否生效

8.SpringBoot整合Mybatis、MP（Mybatis-Plus）完毕，MP：https://mp.baomidou.com/