【Mybatis】（六）****

Mybatis Generator（MBG）通过丰富的配置可以生成不同类型的代码，代码包含了数据库表对应的实体类，Mapper接口类，Mapper XML文件和Example对象等。这些代码文件中几乎包含了全部的单表操作方法，使用MBG可以极大程度上方便我们使用Mybatis。
接下来介绍具体的配置过程：

1、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>

        <!--jdbcConnection：指定如何连接到目标数据库 targetRuntime="MyBatis3Simple"：生成简单版的CRUD targetRuntime="MyBatis3"：生成复杂的CRUD -->
        <context id="DB2Tables" targetRuntime="MyBatis3">
                <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://localhost:3306/mybatis" userId="root" password="13579">
                </jdbcConnection>

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

                <!--javaModelGenerator：指定Javabean的生成策略 targetPackage ="test.model" 目标包名 argetProject = "\ MBGTestProject \ src" 目标工程 -->
                <javaModelGenerator targetPackage ="com.lhk.mybatis.bean" targetProject = ".\src">
                    <property name ="enableSubPackages" value ="true"/>
                    <property name ="trimStrings" value = "true"/>
                </javaModelGenerator>

                <!--sqlMapGenerator：sql映射生成策略 targetPackage ="test.xml" 目标包名 targetProject ="\MBGTestProject\ src" 目标工程 -->
                <sqlMapGenerator targetPackage ="conf" targetProject =".\src">
                    <property name ="enableSubPackages" value ="true"/>
                </sqlMapGenerator>


                <!--javaClientGenerator：指定mapper接口所在的位置 targetPackage = "test.dao" 目标包名 targetProject = "\ MBGTestProject \ src" 目标工程 -->
                <javaClientGenerator type = "XMLMAPPER" targetPackage = "com.lhk.mybatis.dao" targetProject = ".\src">
                    <property name ="enableSubPackages" value ="true"/>
                </javaClientGenerator>

                <!--table：指定要逆向生成的表，根据表要创建Javabean tableName ="tb1_employee" 数据库中的表名 domainObjectName ="Employee" 对应生成的Javabean类名称 -->
                <table tableName ="tb1_employee" domainObjectName ="Employee">
                    <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 tableName="tb1_dept" domainObjectName="Department">
                    <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>

2、添加 mybatis-config.xml

<?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>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 数据库连接的配置信息 驱动，URL，用户名，密码-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
                <property name="username" value="root" />
                <property name="password" value="13579" />
            </dataSource>
        </environment>
    </environments>

    <!-- 将我们写好的sql映射文件（EmployeeMapper.xml）一定要注册到全局配置文件（mybatis-config.xml）中 -->
    <mappers>
        <mapper resource="conf/EmployeeMapper.xml" />
        <mapper resource="conf/DepartmentMapper.xml" />
    </mappers>
</configuration>

3、添加MyBatisTest测试类

用于执行MBG配置生成代码

@Test
    public void testMbg() throws Exception{
        //MBG执行过程中的警告信息
        List<String> warnings = new ArrayList<>();
        //当生成代码重复时，覆盖原代码
        boolean overwrite = true;
        //读取MBG配置文件
        File configFile = new File("E:\\java\\IDEATest\\Mybatis_MBG\\src\\conf\\mbg.xml");

        // ...根据需要填写配置对象......
        ConfigurationParser cp = new ConfigurationParser(warnings);
        Configuration config = cp.parseConfiguration(configFile);

        DefaultShellCallback callback = new DefaultShellCallback(overwrite);

        // 创建MBG
        MyBatisGenerator myBatisGenerator = new MyBatisGenerator(config,callback,warnings);

        // 执行生成代码
        myBatisGenerator.generate(null);
    }

在通过MBG生成代码之前，项目的结构为：

在使用MBG生成代码后，项目的结构为：

可以看到通过MBG自动生成了实体类，Mapper接口类，Mapper XML文件和Example对象。

4、测试自动生成的查询方法

public SqlSessionFactory getSqlSessionFactory() throws IOException {
        String resource = "conf/mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        return new SqlSessionFactoryBuilder().build(inputStream);
    }

 @Test
    public void testSimple() throws IOException {
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        SqlSession openSession = sqlSessionFactory.openSession();
        try {
            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);

            //查询员工名字中有e字母的，和员工性别是0的
            //封装员工查询条件example
            EmployeeExample example = new EmployeeExample();
            //创建一个Criteria，这个Criteria就是拼装查询条件
            EmployeeExample.Criteria criteria = example.createCriteria();
            criteria.andLast_nameLike("%e%");
            criteria.andGenderEqualTo("0");

            //添加or查询，新建一个Criteria，然后example.or(criteria2)
            EmployeeExample.Criteria criteria2 = example.createCriteria();
            criteria2.andEmailLike("%e%");
            example.or(criteria2);

            List<Employee> selectList =  mapper.selectByExample(example);
            for (Employee employee : selectList) {
                System.out.println(employee.getId());
            }
        } finally {
            openSession.close();
        }
    }

查询结果