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MyBatis框架需要：实体类、自定义Mapper接口、Mapper.xml
传统发开中上述三个组件需要开发者手动创建，逆向工程可以帮助开发者自动创建三个组件，减轻开发者的工作量，提高工作效率

如何使用逆向工程

MyBatis Generator，简称MBG，是一个专门为Mybatis框架开发者定制的代码生成器，可自动生成MaBatis框架所需的实体类、Mapper接口和Mappler.xml，支持基本的CRUD操作，但是一些相对复杂的SQL需要开发者自己来完成

• 新建Maven工程，pom.xml

<dependencies>

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis</artifactId>

            <version>3.4.6</version>

        </dependency>

        <dependency>

            <groupId>mysql</groupId>

            <artifactId>mysql-connector-java</artifactId>

            <version>8.0.21</version>

        </dependency>

        <dependency>

            <groupId>org.mybatis.generator</groupId>

            <artifactId>mybatis-generator</artifactId>

            <version>1.3.2</version>

        </dependency>

    </dependencies>

• 创建MBG配置文件generatorConfig.xml

1、jdbcConnect配置数据库连接信息
2、javaModelGenerator配置JavaBean的生成策略
3、sqlMapGenerator配置SQL映射文件生成策略
4、JavaClientGenerator配置Mapper接口的生成策略
5、table配置目标数据表(tbaleName：表名,domainObjectName：JavaBean类名)


<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE generatorConfiguration

        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"

        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">

<generatorConfiguration>

    <context id="mybatis" targetRuntime="MyBatis3">

        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"

                        connectionURL="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"

                        userId="root" password="123456">

        </jdbcConnection>

        <javaModelGenerator targetPackage="com.mybatistest.entity" targetProject=".\src\main\java">

        </javaModelGenerator>

        <sqlMapGenerator targetPackage="com.mybatistest.repository" targetProject=".\src\main\java">

        </sqlMapGenerator>

        <javaClientGenerator type="XMLMAPPER" targetPackage="com.mybatistest.repository" targetProject=".\src\main\java">

        </javaClientGenerator>

        <table tableName="t_user" domainObjectName="User">

        </table>

    </context>

</generatorConfiguration>

• 创建Generator执行类

package com.mybatis.test;

import org.mybatis.generator.api.MyBatisGenerator;

import org.mybatis.generator.config.Configuration;

import org.mybatis.generator.config.xml.ConfigurationParser;

import org.mybatis.generator.exception.InvalidConfigurationException;

import org.mybatis.generator.exception.XMLParserException;

import org.mybatis.generator.internal.DefaultShellCallback;

import java.io.File;

import java.io.IOException;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;

public class Main {

    public static void main(String[] args) {

        List<String>warings = new ArrayList<String>();

        boolean overwrite = true;

        String genCig = "/generatorConfig.xml";

        File configFile = new File(Main.class.getResource(genCig).getFile());

        ConfigurationParser configurationParser = new ConfigurationParser(warings);

        Configuration configuration = null;

        try {

            configuration = configurationParser.parseConfiguration(configFile);

        } catch (IOException e) {

            e.printStackTrace();

        } catch (XMLParserException e) {

            e.printStackTrace();

        }

        DefaultShellCallback callback = new DefaultShellCallback(overwrite);

        MyBatisGenerator myBatisGenerator = null;

        try {

            myBatisGenerator = new MyBatisGenerator(configuration,callback,warings);

        } catch (InvalidConfigurationException e) {

            e.printStackTrace();

        }

        try {

            myBatisGenerator.generate(null);

        } catch (SQLException throwables) {

            throwables.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

}