Mybatis 逆向工程

概述

写javabean对象正常的操作是:根据table写数据库表—>javaBean对象—>BookDao—>dao.xml—>。。。

逆向工程：
根据数据表table，逆向分析数据表，自动生成javaBean—BookDao—dao.xml—xxx

MBG：MyBatis Generator：代码生成器；
MyBatis官方提供的代码生成器；帮我们逆向生成；

实现

1、导包

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

2、写配置

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>

    <!--
    MyBatis3Simple：基础班CRUD
    MyBatis3：复杂版CRUD
     -->
    <context id="DB2Tables" targetRuntime="MyBatis3">
        <commentGenerator>
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!-- jdbcConnection:指导连接到哪个数据库 -->
        <jdbcConnection

                driverClass="com.mysql.cj.jdbc.Driver"
                connectionURL="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8&amp;serverTimezone=UTC"

                userId="root"

                password="123456">
        </jdbcConnection>

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

        <!-- javaModelGenerator：生成pojo

        targetPackage：生成的pojo放在哪个包
        targetProject：放在哪个工程下
        -->
        <javaModelGenerator targetPackage="com.lly.pojo"
                            targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
        </javaModelGenerator>

        <!--sqlMapGenerator：sql映射文件生成器；指定xml生成的地方  -->
        <sqlMapGenerator targetPackage="mapper"
                         targetProject=".\src\main\resources">
            <property name="enableSubPackages" value="true" />
        </sqlMapGenerator>

        <!-- javaClientGenerator：mapper接口生成的地方 -->
        <javaClientGenerator type="XMLMAPPER"
                             targetPackage="com.lly.mapper"

                             targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
        </javaClientGenerator>

        <!-- table：指定要逆向生成哪个数据表
        tableName="t_cat"：表名
        domainObjectName=""：这个表对应的对象名
         -->
        <table tableName="cat" domainObjectName="Cat"></table>
        <table tableName="teacher" domainObjectName="Teacher"></table>

    </context>
</generatorConfiguration>

3、生成

    public static void main(String[] args) throws Exception {
        List<String> warnings = new ArrayList<String>();
        boolean overwrite = true;
        File configFile = new File("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);
        //代码生成
        myBatisGenerator.generate(null);
        System.out.println("生成ok了！");
    }

4、使用插件生成

pom.xml

        <!--使用插件启动mbg-->
        <dependency>
        <groupId>org.mybatis.generator</groupId>
        <artifactId>mybatis-generator-maven-plugin</artifactId>
        <version>1.3.7</version>
        </dependency>


      <!--引入mbg插件-->
      <plugin>
        <groupId>org.mybatis.generator</groupId>
        <artifactId>mybatis-generator-maven-plugin</artifactId>
        <version>1.3.7</version>
        <!--以下依赖不导入的话可能会报以下异常-->
        <dependencies>
          <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.17</version>
          </dependency>
        </dependencies>

        <configuration>
          <verbose>true</verbose>
          <overwrite>true</overwrite>
          <configurationFile>src/main/resources/mbg.xml</configurationFile>
        </configuration>
      </plugin>

[ERROR] Failed to execute goal org.mybatis.generator:mybatis-generator-maven-plugin:1.3.7:
generate (default-cli) on project SSM: Execution default-cli of goal 
org.mybatis.generator:mybatis-generator-maven-plugin:1.3.7:generate failed: 

Exception getting JDBC Driver: com.mysql.cj.jdbc.Driver -> [Help 1]

补充：

用逆向工程可能会造成自己写的文件被清掉哟

分页插件

1、导包

    <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper</artifactId>
      <version>5.2.0</version>
    </dependency>

2、写配置

mybatis-config.xml

    <plugins>
        <plugin interceptor="com.github.pagehelper.PageInterceptor"></plugin>
    </plugins>

3、测试

        PageHelper.startPage(pn,5);
        List<Teacher> list = teacherService.getAll();

        //将查询的结果放在PageInfo()中，这个PageInfo就有非常多能用的东西
        //PageInfo(参数1，参数2)；参数2传入要连续要显示的页码
        PageInfo pageInfo = new PageInfo(list,5);

        System.out.println("当前页码： "+pageInfo.getPageNum());
        System.out.println("总页码： "+pageInfo.getPages());
        System.out.println("总记录数： "+pageInfo.getTotal());
        System.out.println("当前页有几条记录： "+pageInfo.getSize());
        System.out.println("当前页的pageSize： "+pageInfo.getPageSize());
        System.out.println("前一页： "+pageInfo.getPrePage());
        System.out.println("结果： "+pageInfo.getList());//查询结果