MyBaits动态sql语句

1 在接口中书写方法

public interface EmployeeMapperDynamicSQL {

public List<Employee> getEmpsTestInnerParameter(Employee employee);

}

2在映射中进行配置

<!-- 查询员工，要求，携带了哪个字段查询条件就带上这个字段的值 -->
<!-- public List<Employee> getEmpsByConditionIf(Employee employee); -->
<select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
select * from tbl_employee
<!-- where -->
<where>
<!-- test：判断表达式（OGNL）
OGNL参照PPT或者官方文档。
c:if test
从参数中取值进行判断

遇见特殊符号应该去写转义字符：
&&：
-->
<if test="id!=null">
id=#{id}
</if><!-- &amp;为& &quot;为“ -->
<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
and last_name like #{lastName}
</if>
<if test="email!=null and email.trim()!=&quot;&quot;">
and email=#{email}
</if>
<!-- ognl会进行字符串与数字的转换判断 "0"==0 -->
<if test="gender==0 or gender==1">
and gender=#{gender}
</if>
</where>
</select>

3进行测试

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

@Test
public void testDynamicSql() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
//select * from tbl_employee where id=? and last_name like ?
//测试ifwhere
Employee employee = new Employee(null, "jerry2", null, null);
List<Employee> emps = mapper.getEmpsByConditionIf(employee );
for (Employee emp : emps) {
System.out.println(emp);
}
}finally{
openSession.close();
}
}