Mybatis属于半自动ORM，在使用这个框架中，工作量最大的就是书写Mapping的映射文件，由于手动书写很容易出错，我们可以利用Mybatis-Generator来帮我们自动生成文件


关于Mybatis-Generator的下载可以到这个地址：​​https://github.com/mybatis/generator/releases​​


pom.xml添加jar依赖


<!-- https://mvnrepository.com/artifact/org.mybatis.generator/mybatis-generator-core -->
    <dependency>
      <groupId>org.mybatis.generator</groupId>
      <artifactId>mybatis-generator-core</artifactId>
      <version>1.3.5</version>
    </dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.41</version>
    </dependency>

创建表



create table `departments` (
  `DEPARTMENT_ID` int ,
  `DEPARTMENT_NAME` varchar ,
  `MANAGER_ID` int ,
  `LOCATION_ID` int 
);
CREATE TABLE `employees` (
  `EMPLOYEE_ID` int(11) NOT NULL AUTO_INCREMENT,
  `FIRST_NAME` varchar(20) DEFAULT NULL,
  `LAST_NAME` varchar(20) DEFAULT NULL,
  `EMAIL` varchar(20) DEFAULT NULL,
  `PHONE_NUMBER` varchar(20) DEFAULT NULL,
  `HIRE_DATE` date DEFAULT NULL,
  `JOB_ID` int(11) DEFAULT NULL,
  `SALARY` double DEFAULT NULL,
  `COMMISSION_PCT` int(11) DEFAULT NULL,
  `MANAGER_ID` int(11) DEFAULT NULL,
  `DEPARTMENT_ID` int(11) DEFAULT NULL,
  PRIMARY KEY (`EMPLOYEE_ID`)
) ENGINE=InnoDB AUTO_INCREMENT DEFAULT CHARSET=utf8;

编写generator.xml文件



<?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">
      <!-- 不生成注释  -->
    <commentGenerator>
      <property name="suppressAllComments" value="true" />
    </commentGenerator>
    <!-- 配置数据库连接 -->
    <jdbcConnection driverClass="com.mysql.jdbc.Driver"
      connectionURL="jdbc:mysql://localhost:3306/crud" userId="root"
      password="root">
    </jdbcConnection>

    <javaTypeResolver>
      <property name="forceBigDecimals" value="false" />
    </javaTypeResolver>

    <!-- 指定javaBean生成的位置 -->
    <javaModelGenerator targetPackage="com.me.bean"
      targetProject=".\src\main\java">
      <property name="enableSubPackages" value="true" />
      <property name="trimStrings" value="true" />
    </javaModelGenerator>

    <!--指定sql映射文件生成的位置 -->
    <sqlMapGenerator targetPackage="mapper" targetProject=".\src\main\resources">
      <property name="enableSubPackages" value="true" />
    </sqlMapGenerator>

    <!-- 指定dao接口生成的位置，mapper接口 -->
    <javaClientGenerator type="XMLMAPPER"
      targetPackage="com.me.dao" targetProject=".\src\main\java">
      <property name="enableSubPackages" value="true" />
    </javaClientGenerator>


    <!-- table指定每个表的生成策略 -->
    <table tableName="tbl_emp" domainObjectName="Employee"></table>
    <table tableName="tbl_dept" domainObjectName="Department"></table>
  </context>
</generatorConfiguration>

main主方法



import java.io.File;
import java.util.ArrayList;
import java.util.List;

import org.mybatis.generator.api.MyBatisGenerator;
import org.mybatis.generator.config.Configuration;
import org.mybatis.generator.config.xml.ConfigurationParser;
import org.mybatis.generator.internal.DefaultShellCallback;

public class Generator{

  public static void main(String[] args) throws Exception {
    List<String> warnings = new ArrayList<String>();
    boolean overwrite = true;
    File configFile = new File("generator.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);
  }
}

运行后会自动生成javaBean，Mapper Java和xml配置文件


mybatis.generator使用_mysql


注：多表查询语句还是要自己编写

连接多表查询语句的编写

EmployeeMapper接口添加方法，例如


List<Employee> selectByExampleWithDept(EmployeeExample example);

  Employee selectByPrimaryKeyWithDept(Integer empId);

EmployeeMapper.xml编写对应sql查询




把自动selectByPrimaryKey和selectByExample 复制一份稍做修改

就可以了


<!-- List<Employee> selectByExampleWithDept(EmployeeExample example); Employee 
    selectByPrimaryKeyWithDept(Integer empId); -->
    
  <resultMap id="WithDeptResultMap" type="com.me.bean.Employee">
    <id column="emp_id" jdbcType="INTEGER" property="empId" />
    <result column="emp_name" jdbcType="VARCHAR" property="empName" />
    <result column="gender" jdbcType="CHAR" property="gender" />
    <result column="email" jdbcType="VARCHAR" property="email" />
    <result column="d_id" jdbcType="INTEGER" property="dId" />
    <!-- 指定联合查询出部门字段的封装 -->
    <association property="department" javaType="com.me.bean.Department">
      <id column="dept_id" jdbcType="INTEGER" property="deptId" />
      <result column="dept_name" jdbcType="VARCHAR" property="deptName" />
    </association>
  </resultMap>

  <sql id="WithDept_Column_List">
    e.emp_id, e.emp_name, e.gender, e.email, e.d_id, d.dept_id, d.dept_name
  </sql>


  <select id="selectByExampleWithDept" parameterType="com.me.bean.EmployeeExample"
    resultMap="WithDeptResultMap">
    select
    <if test="distinct">
      distinct
    </if>
    <include refid="WithDept_Column_List" />
    FROM tbl_emp e LEFT JOIN tbl_dept d ON e.`d_id`= d.`dept_id`
    <if test="_parameter != null">
      <include refid="Example_Where_Clause" />
    </if>
    <if test="orderByClause != null">
      order by ${orderByClause}
    </if>
  </select>

  <select id="selectByPrimaryKeyWithDept" parameterType="java.lang.Integer"
    resultMap="WithDeptResultMap">
    select
    <include refid="WithDept_Column_List" />
    FROM tbl_emp e LEFT JOIN tbl_dept d ON e.`d_id`= d.`dept_id`
    where emp_id = #{empId,jdbcType=INTEGER}
  </select>


idea mybatis.generator使用

  • ​​ <build> <plugins> <!-- mybatis generator 自动生成代码插件 --> <plugin> <groupId>org.mybatis.generator</groupId> <artifactId>mybatis-generator-maven-plugin</artifactId> <version>1.3.2</version> <configuration> <configurationFile>${basedir}/src/main/resources/generator/generatorConfig.xml</configurationFile> <overwrite>true</overwrite> <verbose>true</verbose> </configuration> </plugin> </plugins> </build>​​在目录下<configurationFile>${basedir}/src/main/resources/generator/generatorConfig.xml</configurationFile>新建generatorConfig.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>
    <!-- 数据库驱动:选择你的本地硬盘上面的数据库驱动包-->
    <classPathEntry  location="D:\java\apache-maven-3.3.9\repo\mysql\mysql-connector-java\5.1.47\mysql-connector-java-5.1.47.jar"/>
    <context id="DB2Tables"  targetRuntime="MyBatis3">
        <commentGenerator>
            <property name="suppressDate" value="true"/>
            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!--数据库链接URL，用户名、密码 -->
        <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://127.0.0.1/mytest?characterEncoding=utf8" userId="root" password="123456">
        </jdbcConnection>
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>
        <!-- 生成模型的包名和位置-->
        <javaModelGenerator targetPackage="com.caffz.model" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>
        <!-- 生成映射文件的包名和位置-->
        <sqlMapGenerator targetPackage="mapping" targetProject="src/main/resources">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>
        <!-- 生成DAO的包名和位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.caffz.mapper" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>
        <!-- 要生成的表 tableName是数据库中的表名或视图名 domainObjectName是实体类名-->
        <table tableName="t_user" domainObjectName="User" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>
    </context>
</generatorConfiguration>



mybatis.generator使用_xml_02


点击右侧栏maven Projects，再打开Plugins插件点击mybatis-generator即可