1、首先加载需要的依赖

 <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.2</version>
    </dependency>
    <dependency>
      <groupId>org.mybatis.generator</groupId>
      <artifactId>mybatis-generator-core</artifactId>
      <version>1.3.7</version>
    </dependency>
  </dependencies>
  <!-- 控制Maven在构建过程中相关配置 -->
  <build>

    <!-- 构建过程中用到的插件 -->
    <plugins>

      <!-- 具体插件，逆向工程的操作是以构建过程中插件形式出现的 -->
      <plugin>
        <groupId>org.mybatis.generator</groupId>
        <artifactId>mybatis-generator-maven-plugin</artifactId>
        <version>1.3.0</version>

        <!-- 插件的依赖 -->
        <dependencies>

          <!-- 逆向工程的核心依赖 -->
          <dependency>
            <groupId>org.mybatis.generator</groupId>
            <artifactId>mybatis-generator-core</artifactId>
            <version>1.3.2</version>
          </dependency>

          <!-- 数据库连接池 -->
          <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.2</version>
          </dependency>

          <!-- MySQL驱动 -->
          <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.8</version>
          </dependency>
        </dependencies>
      </plugin>
    </plugins>
  </build>

2、配置资源文件核心代码如下：

<?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>
    <!-- mybatis-generator:generate -->
    <context id="atguiguTables" targetRuntime="MyBatis3">
        <commentGenerator>
            <!-- 是否去除自动生成的注释 true:是;false:否 -->
            <property name="suppressAllComments" value="true" />
        </commentGenerator>

        <!--数据库连接的信息：驱动类、连接地址、用户名、密码 -->
        <jdbcConnection
                driverClass="com.mysql.jdbc.Driver"
                connectionURL="jdbc:mysql://localhost:3306/project_crowd"
                userId="root"
                password="123">
        </jdbcConnection>

        <!-- 默认false，把JDBC DECIMAL 和 NUMERIC 类型解析为 Integer，为 true时把JDBC DECIMAL
            和 NUMERIC 类型解析为java.math.BigDecimal -->
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false" />
        </javaTypeResolver>

        <!-- targetProject:生成Entity类的路径 -->
        <javaModelGenerator targetProject=".\src\main\java"
                            targetPackage="com.atguigu.crowd.entity">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false" />
            <!-- 从数据库返回的值被清理前后的空格 -->
            <property name="trimStrings" value="true" />
        </javaModelGenerator>

        <!-- targetProject:XxxMapper.xml映射文件生成的路径 -->
        <sqlMapGenerator targetProject=".\src\main\java"
                         targetPackage="com.atguigu.crowd.mapper">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false" />
        </sqlMapGenerator>

        <!-- targetPackage：Mapper接口生成的位置 ，其中targetPackage是自己定义的包路径-->
        <javaClientGenerator type="XMLMAPPER"
                             targetProject=".\src\main\java"
                             targetPackage="com.atguigu.crowd.mapper">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false" />
        </javaClientGenerator>

        <!-- 数据库表名字t_role和我们的entity类对应的映射指定Role -->
        <table tableName="t_role" domainObjectName="Role" />

    </context>
</generatorConfiguration>

3、点击idea右侧maven，双击下面的文件，就会自动生成所需要的资源