詳解mybatis #{}和${}的區別、傳參、基本語法
阿新 • • 發佈:2020-07-22
1 #{}和${}的區別、及注入問題
(1) 區別: 首先清楚一點,動態 SQL 是 mybatis 的強大特性之一,在 mapper 中定義的引數傳到 xml 中之後,在查詢之前 mybatis 會對其進行動態解析,#{} 和 ${} 在預編譯中的處理是不一樣的: 例如:select * from t_user where userName = #{name}; #{}預編譯:用一個佔位符 ? 代替引數:select * from t_user where userName = ? #{}預編譯:會將引數值一起進行編譯:select * from t_user where userName = 'zhangsan' (2) 使用場景: 一般情況首選#{},因為這樣能避免sql注入;如果需要傳參 動態表名、動態欄位名時,需要使用${} 比如:select * from ${tableName} where id > #{id}; (3) SQL注入問題: 舉個例子,如果使用${}出現的注入問題: select * from ${tableName}; 如果傳參 t_user;delete from t_user,則預編譯後的sql如下,將會導致系統不可用: select * from t_user;delete from t_user; (4) like 語句防注入: 使用concat函式: select * from t_user where name like concat('%',#{name},'%')
2 mybatis幾種傳參方式
非註解: (1)單引數: public User getUserByUuid(String uuid); <select id="getUserByUuid" resultMap="BaseResultMap" parameterType="Object"> SELECT * FROM t_user WHERE uuid = #{uuid} </select> (2)多引數 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引數 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)實體物件引數 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集合引數 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> 註解: 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 程式碼 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 判斷字串相等
//JAVA 程式碼 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函式實現 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 大於等於、小於等於
//JAVA程式碼 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>
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