详解mybatis #{}和${}的区别、传参、基本语法

(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}, '%')

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 &gt;= #{startTime} and createTime &lt;= #{endTime}
</select>

//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&amp;&amp;roleList.size()&gt;0">
      AND roleUuid IN
      <foreach collection="roleList" index="index" item="roleUuid" open="(" separator="," close=")">
        #{roleUuid}
      </foreach>
    </when>
    <otherwise>
      AND roleUuid IN ('')
    </otherwise>
   </choose>

//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 &gt;= #{timeStr}
       </if>
       <if test="timeType == '2'.toString()" >
            AND end_time &lt;= #{timeStr}
       </if>
 </select>
或者
<if test = 'timeType== "1"'> </if>

<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>

//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 &gt;= #{startTime} and &lt;= #{startTime}
</select>