MyBatis Generator简称MBG

流程：

导入依赖：

<!--MBG逆向工程-->
<dependency>
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-core</artifactId>
    <version>1.3.7</version>
</dependency>

再resource下创建MBG配置文件mbg.xml

<?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="DB2Tables" targetRuntime="MyBatis3">
        <commentGenerator>
            <!-- 是否去除自动生成的注释 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!-- Mysql数据库连接的信息：驱动类、连接地址、用户名、密码 -->
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/mybatis"
                        userId="root"
                        password="123456">
        </jdbcConnection>
        <!-- Oracle数据库
            <jdbcConnection driverClass="oracle.jdbc.OracleDriver"
                connectionURL="jdbc:oracle:thin:@127.0.0.1:1521:yycg"
                userId="yycg"
                password="yycg">
            </jdbcConnection>
        -->

        <!-- 默认为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POJO类的位置 -->
        <javaModelGenerator targetPackage="com.wang.entity" targetProject=".\src\main\java">
            <!-- 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：mapper映射文件生成的位置 -->
        <sqlMapGenerator targetPackage="com.wang.dao.xml"  targetProject=".\src\main\java">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false" />
        </sqlMapGenerator>

        <!-- targetProject：mapper接口生成的的位置 -->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.wang.dao"  targetProject=".\src\main\java">
            <!-- enableSubPackages:是否让schema作为包的后缀 -->
            <property name="enableSubPackages" value="false" />
        </javaClientGenerator>

        <!-- 指定数据表 -->
        <table schema="" tableName="tbl_employee" domainObjectName="Employee"></table>
        <table schema="" tableName="tbl-department" domaninObjectName="Department"></table>
<!--        <table schema="" tableName="tb_content_category"></table>-->
<!--        <table schema="" tableName="tb_item"></table>-->
<!--        <table schema="" tableName="tb_item_cat"></table>-->
<!--        <table schema="" tableName="tb_item_desc"></table>-->
<!--        <table schema="" tableName="tb_item_param"></table>-->
<!--        <table schema="" tableName="tb_item_param_item"></table>-->
<!--        <table schema="" tableName="tb_order"></table>-->
<!--        <table schema="" tableName="tb_order_item"></table>-->
<!--        <table schema="" tableName="tb_order_shipping"></table>-->
<!--        <table schema="" tableName="tb_user"></table>-->

        <!-- 有些表的字段需要指定java类型
        <table schema="DB2ADMIN" tableName="ALLTYPES" domainObjectName="Customer" >
          <property name="useActualColumnNames" value="true"/>
          <generatedKey column="ID" sqlStatement="DB2" identity="true" />
          <columnOverride column="DATE_FIELD" property="startDate" />
          <ignoreColumn column="FRED" />
          <columnOverride column="LONG_VARCHAR_FIELD" jdbcType="VARCHAR" />
        </table> -->

    </context>
</generatorConfiguration>

生成的代码

@org.junit.Test
public void test1(){
    try{
        List<String> warnings = new ArrayList<String>();
        boolean overwrite = true;
        // 指定配置文件，这里最好是使用绝对路径
        File configFile = new File("D:\\Coding\\IntellijProjects\\mybatis-MBG\\src\\main\\resources\\mbg.xml");
        ConfigurationParser cp = new ConfigurationParser(warnings);
        Configuration config = cp.parseConfiguration(configFile);
        DefaultShellCallback callback = new DefaultShellCallback(overwrite);
        MyBatisGenerator myBatisGenerator = new MyBatisGenerator(config, callback, warnings);
        myBatisGenerator.generate(null);
    }catch (Exception e){
        e.printStackTrace();
    }
}

补充：

自动生成的代码是不会包含有关联查询的，所以需要手动补充

如：

<!--=================补充：带部门的查询=====================-->
<resultMap id="withDepartmentResultMap" type="employee">
  <id column="employee_id" property="employeeId"/>
  <result column="employee_name" property="employeeName"/>
  <result column="gender" property="gender"/>
  <result column="email" property="email"/>
  <result column="department_id" property="departmentId"/>
  <!--分步查询-->
  <!--调用departmentmapper中的selectByPrimaryKey来级联合成-->
  <association property="department"
               select="com.wang.dao.DepartmentMapper.selectByPrimaryKey"
               column="department_id"/>
</resultMap>
<sql id="withDepartment_Column_List">
  e.employee_id,e.employee_name,e.gender,e.email,e.department_id,d.department_name
</sql>


<!--  List<Employee> selectByExampleWithDepartment(EmployeeExample example);-->
<select id="selectByExampleWithDepartment" parameterType="com.wang.pojo.EmployeeExample">
  select
  <if test="distinct">
    distinct
  </if>
  <include refid="withDepartment_Column_List" />
  FROM tbl_employee e
  LEFT JOIN tbl_department d
  ON e.`department_id` = d.`department_id`
  <if test="_parameter != null">
    <include refid="Example_Where_Clause" />
  </if>
  <if test="orderByClause != null">
    order by ${orderByClause}
  </if>
</select>
<!--  Employee selectByPrimaryKeyWithDepartment(Integer employeeId);-->
<select id="selectByPrimaryKeyWithDepartment" parameterType="com.wang.pojo.EmployeeExample">
  select
  <include refid="withDepartment_Column_List" />
  FROM tbl_employee e
  LEFT JOIN tbl_department d
  ON e.`department_id` = d.`department_id`
  where employee_id = #{employeeId,jdbcType=INTEGER}
</select>

mybatis-8-逆向工程