使用set标签可以将动态的配置SET 关键字，和剔除追加到条件末尾的任何不相关的逗号
1.在接口中创建方法
public void updateEmp(Employee employee);
2在映射文件中配置
<!--public void updateEmp(Employee employee); -->
<update >
gender=#{gender}
</if>
</trim>
where id=#{id} -->
</update>
3进行测试
@Test
public void testDynamicSql() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
Employee employee = new Employee(1, null, null, "3");
//测试set标签
mapper.updateEmp(employee);
openSession.commit();
}finally{
openSession.close();
}
}