MyBatis的逆向工程

正向工程：先创建Java实体类，由框架负责根据实体类生成数据库表。Hibernate是支持正向工程的。
逆向工程：先创建数据库表，由框架负责根据数据库表，反向生成如下资源：
- Java实体类
- Mapper接口
- Mapper映射文件

MyBatis Generator

简称MBG，是一个专门为MyBatis框架使用者定制的代码生成器，可以快速的根据表生成对应的映射文件，接口，以及bean类。支持基本的增删改查，以及QBC风格的条件查询。但是表连接、存储过程等这些复杂sql的定义需要我们手工编写

创建逆向工程的步骤

添加依赖和插件

<!-- 依赖MyBatis核心包 -->
  <dependencies>
      <dependency>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
          <version>3.5.7</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>
                    <dependency>
                      <groupId>log4j</groupId>
                      <artifactId>log4j</artifactId>
                      <version>1.2.14</version>
                      <optional>true</optional>
      			</dependency>
              </dependencies>
          </plugin>
      </plugins>
  </build>

创建MyBatis的核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <properties resource="jdbc.properties"/>

    <typeAliases>
        <package name="com.frx01.mybatis.pojo"/>
    </typeAliases>

    <plugins>
        <!--设置分页插件-->
        <plugin interceptor="com.github.pagehelper.PageInterceptor"></plugin>
    </plugins>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <package name="com.frx01.mybatis.mapper"/>
    </mappers>
</configuration>

创建逆向工程的配置文件

文件名必须是：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>
    <!--
            targetRuntime: 执行生成的逆向工程的版本
                    MyBatis3Simple: 生成基本的CRUD（清新简洁版）
                    MyBatis3: 生成带条件的CRUD（奢华尊享版）
     -->
    <context id="DB2Tables" targetRuntime="MyBatis3">
        <!-- 数据库的连接信息 -->
        <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/mybatis"
                        userId="root"
                        password="hsp">
        </jdbcConnection>
        <!-- javaBean的生成策略-->
        <javaModelGenerator targetPackage="com.frx01.mybatis.pojo" targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
        </javaModelGenerator>
        <!-- SQL映射文件的生成策略 -->
        <sqlMapGenerator targetPackage="com.frx01.mybatis.mapper"  targetProject=".\src\main\resources">
            <property name="enableSubPackages" value="true" />
        </sqlMapGenerator>
        <!-- Mapper接口的生成策略 -->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.frx01.mybatis.mapper"  targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
        </javaClientGenerator>
        <!-- 逆向分析的表 -->
        <!-- tableName设置为*号，可以对应所有表，此时不写domainObjectName -->
        <!-- domainObjectName属性指定生成出来的实体类的类名 -->
        <table tableName="t_emp" domainObjectName="Emp"/>
        <table tableName="t_dept" domainObjectName="Dept"/>
    </context>
</generatorConfiguration>

执行MBG插件的generate目标

清新简洁版效果:

奢华尊享版效果:

测试

public class MBGTest {

    @Test
    public void testMBG() {
        try {

            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
            SqlSession openSession = sqlSessionFactory.openSession(true);
            EmpMapper mapper = openSession.getMapper(EmpMapper.class);
            //查询数据
            Emp emp = mapper.selectByPrimaryKey(3);
            System.out.println(emp);
        }catch (IOException e){
            e.printStackTrace();
        }
    }
}

结果

DEBUG 02-28 11:28:40,132 ==>  Preparing: select id, last_name, gender, email, d_id from tbl_employee where id = ?  (BaseJdbcLogger.java:137) 
DEBUG 02-28 11:28:40,185 ==> Parameters: 3(Integer)  (BaseJdbcLogger.java:137) 
DEBUG 02-28 11:28:40,219 <==      Total: 1  (BaseJdbcLogger.java:137) 
Emp{id=3, lastName='jerry', gender='1', email='jerry@123.com', dId=null}

Process finished with exit code 0

QBC查询

根据条件查询

@Test
public void testMBG() {
    try {

        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        SqlSession openSession = sqlSessionFactory.openSession(true);
        EmpMapper mapper = openSession.getMapper(EmpMapper.class);
        //根据条件查询
        EmpExample example = new EmpExample();
        example.createCriteria().andLastNameEqualTo("frank").andGenderEqualTo("1");
        List<Emp> list = mapper.selectByExample(example);
        for (Emp emp : list) {
            System.out.println(emp);
        }
    }catch (IOException e){
        e.printStackTrace();
    }

}

结果

DEBUG 02-28 11:27:59,060 ==>  Preparing: select id, last_name, gender, email, d_id from tbl_employee WHERE ( last_name = ? and gender = ? )  (BaseJdbcLogger.java:137) 
DEBUG 02-28 11:27:59,102 ==> Parameters: frank(String), 1(String)  (BaseJdbcLogger.java:137) 
DEBUG 02-28 11:27:59,136 <==      Total: 1  (BaseJdbcLogger.java:137) 
Emp{id=5, lastName='frank', gender='1', email='frank@athome.com', dId=2}

Process finished with exit code 0

根据主键修改

@Test
public void testMBG() {
    try {

        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        SqlSession openSession = sqlSessionFactory.openSession(true);
        EmpMapper mapper = openSession.getMapper(EmpMapper.class);
        //根据主键修改
        mapper.updateByPrimaryKey(new Emp(1,"admin","1","123@qq.com",1));
    }catch (IOException e){
        e.printStackTrace();
    }

}

结果

DEBUG 02-28 11:39:37,371 ==>  Preparing: update tbl_employee set last_name = ?, gender = ?, email = ?, d_id = ? where id = ?  (BaseJdbcLogger.java:137) 
DEBUG 02-28 11:39:37,431 ==> Parameters: admin(String), 1(String), 123@qq.com(String), 1(Integer), 1(Integer)  (BaseJdbcLogger.java:137) 
DEBUG 02-28 11:39:37,831 <==    Updates: 1  (BaseJdbcLogger.java:137) 

Process finished with exit code 0