Mybatis、Mybatis Generator、Mybatis-Plus、Mybatis Plus Generator

1、介绍

Mybatis

Mybatis 是操作数据库的框架：提供一种Mapper类，支持用Java代码对数据库进行增删改查。

缺点：需要先在xml中写好SQL语句；

Mybatis Generator

自动为Mybatis生成简单的增删改查SQL语句的工具

Mybatis-Plus

MyBatis-Plus 是一个Mybatis 增强版工具，在 MyBatis 基础上扩充了功能（由国人团队苞米豆开发）。
作用：为了简化开发效率。

Mybatis Plus Generator

比Mybatis Generator更加强大，支持功能更多，可自动生成：
Entity、Mapper、Service、Controller等

2、Mybatis Plus Generator用法演示

2.1、工程创建与依赖配置

通过IDEA新建Spring工程，在工程的pom.xml文件中配置依赖：

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</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>

        <!--mp-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.2.0</version>
        </dependency>
        <!--模板-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-freemarker</artifactId>
        </dependency>
        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!--mp代码生成器-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-generator</artifactId>
            <version>3.2.0</version>
        </dependency>
    </dependencies>

2.2、数据库构建与项目配置

使用Navicat创建mysql数据库 “vueblog”，创建数据表，SQL语句（自己懒得写，参考某大神的现成的SQL）：

CREATE TABLE `m_user` (
 `id` bigint(20) NOT NULL AUTO_INCREMENT,
 `username` varchar(64) DEFAULT NULL,
 `avatar` varchar(255) DEFAULT NULL,
 `email` varchar(64) DEFAULT NULL,
 `password` varchar(64) DEFAULT NULL,
 `status` int(5) NOT NULL,
 `created` datetime DEFAULT NULL,
 `last_login` datetime DEFAULT NULL,
 PRIMARY KEY (`id`),
 KEY `UK_USERNAME` (`username`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE `m_blog` (
 `id` bigint(20) NOT NULL AUTO_INCREMENT,
 `user_id` bigint(20) NOT NULL,
 `title` varchar(255) NOT NULL,
 `description` varchar(255) NOT NULL,
 `content` longtext,
 `created` datetime NOT NULL ON UPDATE CURRENT_TIMESTAMP,
 `status` tinyint(4) DEFAULT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8mb4;

INSERT INTO `vueblog`.`m_user` (`id`, `username`, `avatar`, `email`, `password`, `status`, `created`, `last_login`) VALUES ('1', 'test', 'https://image-1300566513.cos.ap-guangzhou.myqcloud.com/upload/images/5a9f48118166308daba8b6da7e466aab.jpg', NULL, '96e79218965eb72c92a549dd5a330112', '0', '2020-04-20 10:44:01', NULL);

在工程的application.properties中，配置数据源datasource与mybatis-plus：

server.port=8080

# DataSource Config
spring.datasource.url=jdbc:mysql://localhost:3306/vueblog?useUnicode=true&useSSL=false&characterEncoding=utf8
spring.datasource.username=root
spring.datasource.password=qixingchao
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

mybatis-plus.mapper-locations=classpath*:/mapper/**Mapper.xml

2.3、导入、调整CodeGenerator源码

注意：数据源、包名信息一定要根据自己项目信息进行调整

package com.qxc;

import com.baomidou.mybatisplus.core.exceptions.MybatisPlusException;
import com.baomidou.mybatisplus.core.toolkit.StringPool;
import com.baomidou.mybatisplus.core.toolkit.StringUtils;
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 java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class CodeGenerator {

    /**
     * <p>
     * 读取控制台内容
     * </p>
     */
    public static String scanner(String tip) {
        Scanner scanner = new Scanner(System.in);
        StringBuilder help = new StringBuilder();
        help.append("请输入" + tip + "：");
        System.out.println(help.toString());
        if (scanner.hasNext()) {
            String ipt = scanner.next();
            if (StringUtils.isNotEmpty(ipt)) {
                return ipt;
            }
        }
        throw new MybatisPlusException("请输入正确的" + tip + "！");
    }

    public static void main(String[] args) {
        // 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("qixingchao");
        gc.setOpen(false);
        gc.setServiceName("%sService");
        mpg.setGlobalConfig(gc);

        // 数据源配置
        DataSourceConfig dsc = new DataSourceConfig();
        dsc.setUrl("jdbc:mysql://localhost:3306/vueblog?useUnicode=true&useSSL=false&characterEncoding=utf8&serverTimezone=UTC");
        dsc.setDriverName("com.mysql.cj.jdbc.Driver");
        dsc.setUsername("root");
        dsc.setPassword("qixingchao");
        mpg.setDataSource(dsc);

        // 包配置
        PackageConfig pc = new PackageConfig();
        pc.setModuleName(null);
        pc.setParent("com.qxc");
        mpg.setPackageInfo(pc);

        // 自定义配置
        InjectionConfig cfg = new InjectionConfig() {
            @Override
            public void initMap() {
                // to do nothing
            }
        };

        // 如果模板引擎是 freemarker
        String templatePath = "/templates/mapper.xml.ftl";
        // 如果模板引擎是 velocity
        // String templatePath = "/templates/mapper.xml.vm";

        // 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(templatePath) {
            @Override
            public String outputFile(TableInfo tableInfo) {
                // 自定义输出文件名 ， 如果你 Entity 设置了前后缀、此处注意 xml 的名称会跟着发生变化！！
                return projectPath + "/src/main/resources/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(true);
        strategy.setRestControllerStyle(true);
        strategy.setInclude(scanner("表名，多个英文逗号分割").split(","));
        strategy.setControllerMappingHyphenStyle(true);
        strategy.setTablePrefix("m_");
        mpg.setStrategy(strategy);
        mpg.setTemplateEngine(new FreemarkerTemplateEngine());
        mpg.execute();
    }
}

2.4 执行CodeGenerator

右键CodeGenerator.java类 --> 选择"Run 'CodeGenerator.main()' "

IDEA底部弹出输入面板，手动输入数据库表名：

回车，自动生成基础代码：

2.5 代码测试

工程Application类增加自动扫描代码MapperScan：

package com.qxc;

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

@SpringBootApplication
@MapperScan("com.qxc.mapper")
public class VueblogApplication {
    public static void main(String[] args) {
        SpringApplication.run(VueblogApplication.class, args);
    }
}

UserController类里写接口测试方法：

package com.qxc.controller;

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

import org.springframework.web.bind.annotation.RestController;

/**
 * <p>
 *  前端控制器
 * </p>
 *
 * @author qixingchao
 * @since 2021-04-12
 */
@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    UserService userService;

    @GetMapping("/{id}")
    public Object getUserById(@PathVariable("id")long id){
        return userService.getById(id);
    }
}

通过IDEA启动工程，在浏览器输入与接口匹配的URL地址：