mybatis的代码生成器--generator

作用：根据数据库中表自动生成实体类，dao层和xml映射文件完成简单的增删改查。
官网:http://mybatis.org/generator/

实例：完成两张表的自动化创建实体类，dao层，mapper层
前置条件
第一张表：tbl_user

/*
 Navicat Premium Data Transfer

 Source Server         : Michinaish
 Source Server Type    : MySQL
 Source Server Version : 80011
 Source Host           : localhost:3306
 Source Schema         : mybatis

 Target Server Type    : MySQL
 Target Server Version : 80011
 File Encoding         : 65001

 Date: 06/06/2022 19:27:10
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for tbl_user
-- ----------------------------
DROP TABLE IF EXISTS `tbl_user`;
CREATE TABLE `tbl_user`  (
  `id` int(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
  `name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '姓名',
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '邮箱',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 12 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of tbl_user
-- ----------------------------
INSERT INTO `tbl_user` VALUES (2, 'zs', '[email protected]');
INSERT INTO `tbl_user` VALUES (4, 'ls', '[email protected]');
INSERT INTO `tbl_user` VALUES (5, 'ww', '[email protected]');
INSERT INTO `tbl_user` VALUES (8, 'll', '[email protected]');
INSERT INTO `tbl_user` VALUES (9, 'mary', '[email protected]');
INSERT INTO `tbl_user` VALUES (10, 'kangkang', '[email protected]');
INSERT INTO `tbl_user` VALUES (11, 'kangkang', '[email protected]');
INSERT INTO `tbl_user` VALUES (12, 'mary', '[email protected]');

SET FOREIGN_KEY_CHECKS = 1;

第二张表:tb_stu

/*
 Navicat Premium Data Transfer

 Source Server         : Michinaish
 Source Server Type    : MySQL
 Source Server Version : 80011
 Source Host           : localhost:3306
 Source Schema         : mybatis

 Target Server Type    : MySQL
 Target Server Version : 80011
 File Encoding         : 65001

 Date: 06/06/2022 19:28:13
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for tb_stu
-- ----------------------------
DROP TABLE IF EXISTS `tb_stu`;
CREATE TABLE `tb_stu`  (
  `stu_id` int(11) NOT NULL AUTO_INCREMENT,
  `stu_name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
  `stu_age` int(255) NULL DEFAULT NULL,
  `stu_sex` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
  `cid` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`stu_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of tb_stu
-- ----------------------------
INSERT INTO `tb_stu` VALUES (1, '张三', 18, '男', 1);
INSERT INTO `tb_stu` VALUES (2, '李四', 19, '女', 2);
INSERT INTO `tb_stu` VALUES (3, '田七', 20, '男', 3);
INSERT INTO `tb_stu` VALUES (5, '赵六', 0, '女', 3);
INSERT INTO `tb_stu` VALUES (6, '赵六', 0, '女', 1);
INSERT INTO `tb_stu` VALUES (8, '赵六', 0, '女', 2);
SET FOREIGN_KEY_CHECKS = 1;

使用步骤
第一步：(1)引入mybatis-generator的依赖jar包。

<dependency>
            <groupId>repMaven.org.mybatis.generatorgroupId>
            <artifactId>mybatis-generator-coreartifactId>
            <version>1.4.0version>
dependency>

第二步:配置文件 generator.xml
注意:

<?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>

    <!--mysql驱动jar的位置 直到找到 mysql-connector-java-8.0.16.jar 版本不一致 但是为.jar结尾-->
    <classPathEntry location="D:\repMaven\mysql\mysql-connector-java\8.0.16\mysql-connector-java-8.0.16.jar" />

    <context id="DB2Tables" targetRuntime="MyBatis3">

        <!--数据库的配置信息-->
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/mybatis?serverTimezone=Asia/Shanghai"
                        userId="root"
                        password="root">
        </jdbcConnection>

        <!--Java实体类的配置信息
        targetPackage:目标包  实体类的位置是在java下
        targetProject:目标工程  src下 java之前
         -->
        <javaModelGenerator targetPackage="com.wx.entity" targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
        </javaModelGenerator>


        <!--映射文件的配置信息-->
        <sqlMapGenerator targetPackage="mapper"  targetProject=".\src\main\resources">
            <property name="enableSubPackages" value="true" />
        </sqlMapGenerator>

        <!--dao层的配置信息-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.wx.dao"  targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
        </javaClientGenerator>

        <!--
            schema:数据库名
            tableName:表名
            domainObjectName:实体类名

            这四个一般为false 不然回生成复杂的增删改查操作
            enableSelectByExample="false" 是否生成复杂的查询操作
            enableCountByExample="false"   
            enableDeleteByExample="false"
            enableUpdateByExample="false">
        -->
        <table schema="mybatis" tableName="tbl_user" domainObjectName="User"
               enableSelectByExample="false"
               enableCountByExample="false"
               enableDeleteByExample="false"
               enableUpdateByExample="false">
            <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>

        <table schema="mybatis" tableName="tb_stu" domainObjectName="Student"
               enableSelectByExample="false"
               enableCountByExample="false"
               enableDeleteByExample="false"
               enableUpdateByExample="false">
            <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>

第三步:在单元测试中或者在main函数中运行配置文件 生成实体层 dao层 mapper层

    @Test
    public void test01() 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);
    }

注意 生成的实体层 dao层 mapper层会有注释 这时候可以使用如下代码消除注释

		//抑制注释
        <commentGenerator>
            <property name="suppressAllComments" value="true" />
        </commentGenerator>

整体结构图为:

优化：自动生成的实体类名字和自己的数据库中表中列名一致 在idea中看着非常别扭
比如Student实体类

优化的地方
（1）重新写Student实体类中的属性
通过lombok简化代码书写

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {
    private Integer stuId;
    private String stuName;
    private Integer stuAge;
    private String stuSex;
    private Integer cid;
}

修改后为:

测试自动生成的代码

    /*通过主键删除某个学生对象*/
    @Test
    public void testStudentFindAll() throws Exception{
        Reader rd = Resources.getResourceAsReader("conf.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(rd);
        SqlSession session = factory.openSession();
        StudentMapper sm = session.getMapper(StudentMapper.class);
        int row = sm.deleteByPrimaryKey(8);
        System.out.println(row);
        session.commit();
        session.close();
    }

运行图:

其余的代码自行测试即可