注解開發 · JAVA

[TOC] # 配置 **用了注解,xml就不要用了,用了就會報錯** SqlMapConfig.xml ~~~  <mappers> <package name="com.jdxia.dao"/> </mappers> ~~~ # 增刪改查 ## 增加 ~~~ /** * 保存用戶 * @param user */ @Insert("insert into user(username, address, sex, birthday) values " + "(#{username}, #{address}, #{sex}, #{birthday})") void saveUser(User user); ~~~ ## 更改 ~~~ /** * 更改用戶 * @param user */ @Update("update user set username=#{username}, sex=#{sex}, birthday=#{birthday} where id=#{id}") void updateUser(User user); ~~~ # 別名 ~~~ /** * 查詢所有用戶 * @return */ @Select("select * from user") @Results( id = "userMap", value = { @Result(id=true, column = "id", property = "id"), @Result(column = "username", property = "username"), @Result(column = "address", property = "address") } ) List<User> findAll(); ~~~ 設置的別名也可以使用 ~~~ /** * 保存用戶 * @param user */ @Insert("insert into user(username, address, sex, birthday) values " + "(#{username}, #{address}, #{sex}, #{birthday})") @ResultMap(value = {"userMap"}) void saveUser(User user); ~~~ 也可以寫成這樣 ~~~ @ResultMap("userMap") ~~~ 只有value,{}只有一個元素,可以省略 # 關聯關系 ## 一對一 one是一對一 fetchType是是否延遲加載 ~~~ /** * 查詢所有賬戶，并且獲取每個賬戶所屬的用戶信息 * @return */ @Select("select * from account") @Results(id="accountMap",value = { @Result(id=true,column = "id",property = "id"), @Result(column = "uid",property = "uid"), @Result(column = "money",property = "money"), @Result(property = "user",column = "uid",one=@One(select="com.jdxia.dao.IUserDao.findById",fetchType= FetchType.EAGER)) }) List<Account> findAll(); ~~~ ## 一對多 ~~~ /** * 查詢所有用戶 * @return */ @Select("select * from user") @Results(id="userMap",value={ @Result(id=true,column = "id",property = "userId"), @Result(column = "username",property = "userName"), @Result(column = "address",property = "userAddress"), @Result(column = "sex",property = "userSex"), @Result(column = "birthday",property = "userBirthday"), @Result(property = "accounts",column = "id", many = @Many(select = "com.jdxia.dao.IAccountDao.findAccountByUid", fetchType = FetchType.LAZY)) }) List<User> findAll(); ~~~ # 二級緩存 SqlMapConfig.xml還是需要配置一下的 ~~~ @CacheNamespace(blocking = true) public interface IUserDao { ~~~ # options注解第一個使用場景：有一個表 ~~~ CREATE TABLE instance ( instance_id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT COMMENT '主鍵id', infos VARCHAR(2048) NOT NULL DEFAULT '' COMMENT '', create_time TIMESTAMP NOT NULL DEFAULT '0000-00-00 00:00:00' COMMENT '創建時間', update_time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新時間', PRIMARY KEY (instance_id) )ENGINE=INNODB DEFAULT CHARSET=utf8 COMMENT '實例表'; ~~~ 其中的instance\_id是自增的主鍵。我希望通過dao層的接口插入的數據能夠返回主鍵的id：接口代碼如下： ~~~ @Insert("insert into instance (infos)" + " (" + " @{infos}," + " NOW()" + ")") @Options(useGeneratedKeys = true, keyProperty = "instanceId", keyColumn = "instance_id") int addInstance(Instance instance); ~~~ `@Options`注解中默認設置的主鍵對應的字段名為id、在我們的表中，主鍵名為instance\_id，因此需要將keyProperty和keyColumn設置成我們想要的字段：這個注解的意思就是，從instance\_id這個字段里面把數據放到傳入對象的instanceId成員變量里面。我們來看下@Option注解的源碼：注解中的useCache還可以設置緩存相關的選項： useCache = true表示本次查詢結果被緩存以提高下次查詢速度，flushCache = false表示下次查詢時不刷新緩存，timeout = 10000表示查詢結果緩存10000秒。 # selectKey注解 [https://www.cnblogs.com/weiyinfu/p/6835301.html](https://www.cnblogs.com/weiyinfu/p/6835301.html) 注解大全 [https://blog.csdn.net/weixin\_39805338/article/details/80759155](https://blog.csdn.net/weixin_39805338/article/details/80759155)