1 #{}和${}的区别、及注入问题
(1) 区别：
首先清楚一点，动态 SQL 是 mybatis 的强大特性之一，在 mapper 中定义的参数传到 xml 中之后，在查询之前 mybatis 会对其进行动态解析，#{} 和 ${} 在预编译中的处理是不一样的：
例如：select * from t_user where userName = #{name};
#{}预编译：用一个占位符 ? 代替参数:select * from t_user where userName = ?
#{}预编译：会将参数值一起进行编译：select * from t_user where userName = 'zhangsan'
(2) 使用场景：
一般情况首选#{}，因为这样能避免sql注入；如果需要传参 动态表名、动态字段名时，需要使用${}
比如：select * from ${tableName} where id > #{id};
(3) SQL注入问题：
举个例子，如果使用${}出现的注入问题：
select * from ${tableName};
如果传参 t_user;delete from t_user，则预编译后的sql如下，将会导致系统不可用：
select * from t_user;delete from t_user;
(4) like 语句防注入：
使用concat函数：
select * from t_user where name like concat('%', #{name}, '%')
2 mybatis几种传参方式
非注解：
(1)单参数：
public User getUserByUuid(String uuid);
<select id="getUserByUuid" resultMap="BaseResultMap" parameterType="Object">
SELECT * FROM t_user WHERE uuid = #{uuid}
</select>
(2)多参数
public User getUserByNameAndPass(String name,String pass);
<select id="getUserByNameAndPass" resultMap="BaseResultMap" parameterType="Object">
SELECT * FROM t_user WHERE t_name = #{0} and t_pass = #{1}
</select>
(3)Map参数
public User getUserByMap(Map<String,Object> map);
<select id="getUserByMap" resultMap="BaseResultMap" parameterType="java.util.Map">
SELECT * FROM t_user WHERE t_name = #{name} and t_pass = #{pass}
</select>
(4)实体对象参数
public int updateUser(User user);
<select id="updateUser" resultMap="BaseResultMap" parameterType="Object">
update t_user set t_name = #{name}, t_pass = #{pass} where uuid=#{uuid}
</select>
(4)List集合参数
public int batchDelUser(List<String> uuidList);
<delete id="batchDelUser" parameterType="java.util.List">
DELETE FROM t_user WHERE uuid IN
<foreach collection="list" index="index" item="uuid" open="(" separator="," close=")">
#{uuid}
</foreach>
</delete>
注解：
public List<User> getUserByTime(@Param("startTime")String startTime, @Param("endTime")String endTime);
<select id="getUserByTime" resultMap="BaseResultMap" parameterType="Object">
SELECT * from t_user where createTime >= #{startTime} and createTime <= #{endTime}
</select>
2 choose when otherwise
//JAVA 代码
public List<Group> getUserRoleRelByUserUuid(@Param("groupUuid") String userUuid,@Param("roleList")List<String> roleUuidList);
//SQL
SELECT * from user_role where groupUuid=#{groupUuid}
<choose>
<when test="roleList!=null&&roleList.size()>0">
AND roleUuid IN
<foreach collection="roleList" index="index" item="roleUuid" open="(" separator="," close=")">
#{roleUuid}
</foreach>
</when>
<otherwise>
AND roleUuid IN ('')
</otherwise>
</choose>
3 判断字符串相等
//JAVA 代码
public int getOrderCountByParams(Map<String, Object> params);
//SQL
<select id="getOrderCountByParams" resultType="java.lang.Integer" parameterType="Object">
SELECT count(*) FROM itil_publish_order where 1=1
<if test="timeType == '1'.toString()" >
AND create_time >= #{timeStr}
</if>
<if test="timeType == '2'.toString()" >
AND end_time <= #{timeStr}
</if>
</select>
或者
<if test = 'timeType== "1"'> </if>
4 CONCAT函数实现 模糊匹配
<select id="getMaxSerialCode" resultType="java.lang.String" parameterType="Object">
SELECT count(*) FROM
itil_publish_order
WHERE serial_code LIKE CONCAT('%',#{codeStr},'%')
ORDER BY serial_code DESC LIMIT 1
</select>
5 大于等于、小于等于
//JAVA代码
public List<PublishOrder> getOrderCount(@Param("startTime") String startTime,@Param("startTime")List<String> startTime);
//SQL
<select id="getOrderCount" resultType="java.lang.String" parameterType="Object">
SELECT * FROM itil_publish_order
WHERE createTime >= #{startTime} and <= #{startTime}
</select>
