MyBatis_[tp_48]_动态sql_内置参数_parameter&_databaseId

笔记要点-----内置参数_parameter&_databaseId      用处: 迅速切换数据库,执行一条多分支的sql语句即可;
1.定义接口

public interface EmployeeMapper_DynamicSQL {
    public List<Employee> getEmpsTestInnerParameter(Employee employee);//测试内部参数
}

2.定义XML映射文件

    <!--两个内置参数;不只是方法传递过来的参数可以用来判断,取值
        mubatis默认还有两个内置参数:
        _parameter : 代表整个参数;
            单个参数: _parameter就是这个参数
            多个参数: 会被封装成一个map,map就是_parameter

        _databaseId : 如果配置了databaseIdProvider标签;
            _databaseId就是代表了当前数据库的别名mysql !
        -->
    <!--public List<Employee> getEmpsTestInnerParameter(Employee employee);//测试内部参数-->
    <select id="getEmpsTestInnerParameter" resultType="com.bean.Employee">
        <if test="_databaseId=='mysql'">
            select * from tbl_employee
            <if test="_parameter!=null">
                where last_name = #{_parameter.lastName}
            </if>
        </if>
        <if test="_databaseId=='oracle'">
            select * from tbl_employee
        </if>

3.编写测试代码

public class test_tp48 {
    public SqlSessionFactory getSqlSessionFactory() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        return new SqlSessionFactoryBuilder().build(inputStream);
    }

    @Test
    public void test11() throws Exception {
        SqlSession openSession = getSqlSessionFactory().openSession();
        try {
            System.out.println("++++++++++---- tp48.测试动态sql_内置参数_parameter&_databaseId");
            EmployeeMapper_DynamicSQL mapper = openSession.getMapper(EmployeeMapper_DynamicSQL.class);
            List<Employee> list = mapper.getEmpsTestInnerParameter(null);
            for(Employee e:list)
                System.out.println(e);

            openSession.commit();
        } finally {
            openSession.close();
        }
    }
}

测试结果

++++++++++---- tp48.测试动态sql_内置参数_parameter&_databaseId
DEBUG 12-05 17:45:17,805 ==>  Preparing: select * from tbl_employee   (BaseJdbcLogger.java:145)
DEBUG 12-05 17:45:17,828 ==> Parameters:   (BaseJdbcLogger.java:145)
DEBUG 12-05 17:45:17,845 <==      Total: 8  (BaseJdbcLogger.java:145)
Employee{id=1, lastName='Jerry2333', email='233@...', gender='1', dept=null}
Employee{id=4, lastName='葫芦娃', email='葫芦娃@163.com', gender='0', dept=null}
Employee{id=5, lastName='葫芦娃e', email='qwq@qq.com', gender='1', dept=null}
Employee{id=6, lastName='null', email='xxx@qq.com', gender='1', dept=null}
Employee{id=7, lastName='tom', email='tom@163.com', gender='0', dept=null}
Employee{id=8, lastName='frak', email='frak@163.com', gender='1', dept=null}
Employee{id=9, lastName='smith', email='smith@qq.com', gender='1', dept=null}
Employee{id=10, lastName='aliex', email='aliex@qq.com', gender='0', dept=null}