MyBatis Plus wapper介绍

超、凢脫俗 2024-04-03 08:15 89阅读 0赞

**Wrapper ： 条件构造抽象类，最顶端父类**

*  AbstractWrapper ： 用于查询条件封装，生成 sql 的 where 条件
 *  QueryWrapper ： 查询条件封装
 *  UpdateWrapper ： Update 条件封装
 *  AbstractLambdaWrapper ： 使用Lambda 语法
 *  LambdaQueryWrapper ：用于Lambda语法使用的查询Wrapper
 *  LambdaUpdateWrapper ： Lambda 更新封装Wrapper

**测试用例** ge、gt、le、lt、isNull、isNotNull

@Test
 public void testQuery() {
 QueryWrapper<User>queryWrapper = newQueryWrapper<>();
 queryWrapper
 .isNull("name")
 .ge("age", 12)
 .isNotNull("email");
 int result = userMapper.delete(queryWrapper);
 System.out.println("delete return count = " + result);
 }

**eq、ne,注意：seletOne()返回的是一条实体记录，当出现多条时会报错**

@Test
 public void testSelectOne() {
 QueryWrapper<User>queryWrapper = newQueryWrapper<>();
 queryWrapper.eq("name", "Tom");
 Useruser = userMapper.selectOne(queryWrapper);//只能返回一条记录，多余一条则抛出异常
 System.out.println(user);
 }

####  **between、notBetween**,包含大小边界 ####

@Test
 public void testSelectCount() {
 QueryWrapper<User>queryWrapper = newQueryWrapper<>();
 queryWrapper.between("age", 20, 30);
 Integer count = userMapper.selectCount(queryWrapper); //返回数据数量
 System.out.println(count);
 }

like、notLike、likeLeft、likeRight,selectMaps()返回Map集合列表，通常配合select()使用

@Test
 public void testSelectMaps() {
 QueryWrapper<User>queryWrapper = newQueryWrapper<>();
 queryWrapper
 .select("name", "age")
 .like("name", "e")
 .likeRight("email", "5");
 List<Map<String, Object>>maps = userMapper.selectMaps(queryWrapper);//返回值是Map列表
 maps.forEach(System.out::println);
 }

orderBy、orderByDesc、orderByAsc

@Test
 public void testSelectListOrderBy() {
 QueryWrapper<User>queryWrapper = newQueryWrapper<>();
 queryWrapper.orderByDesc("age", "id");
 List<User>users = userMapper.selectList(queryWrapper);
 users.forEach(System.out::println);
 }

<table style="margin-left:6.75pt;"> 
 <tbody> 
 <tr> 
 <td style="vertical-align:top;"> 查询方式 </td> 
 <td style="vertical-align:top;"> 说明 </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> setSqlSelect </td> 
 <td style="background-color:#f1f1f1;"> 设置 SELECT 查询字段 </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> where </td> 
 <td style="vertical-align:top;"> WHERE 语句，拼接 +&nbsp;WHERE 条件 </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> and </td> 
 <td style="background-color:#f1f1f1;"> AND 语句，拼接 +&nbsp;AND 字段=值 </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> andNew </td> 
 <td style="vertical-align:top;"> AND 语句，拼接 +&nbsp;AND (字段=值) </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> or </td> 
 <td style="background-color:#f1f1f1;"> OR 语句，拼接 +&nbsp;OR 字段=值 </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> orNew </td> 
 <td style="vertical-align:top;"> OR 语句，拼接 +&nbsp;OR (字段=值) </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> eq </td> 
 <td style="background-color:#f1f1f1;"> 等于= </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> allEq </td> 
 <td style="vertical-align:top;"> 基于 map 内容等于= </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> ne </td> 
 <td style="background-color:#f1f1f1;"> 不等于&lt;&gt; </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> gt </td> 
 <td style="vertical-align:top;"> 大于&gt; </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> ge </td> 
 <td style="background-color:#f1f1f1;"> 大于等于&gt;= </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> lt </td> 
 <td style="vertical-align:top;"> 小于&lt; </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> le </td> 
 <td style="background-color:#f1f1f1;"> 小于等于&lt;= </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> like </td> 
 <td style="vertical-align:top;"> 模糊查询 LIKE </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> notLike </td> 
 <td style="background-color:#f1f1f1;"> 模糊查询 NOT LIKE </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> in </td> 
 <td style="vertical-align:top;"> IN 查询 </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> notIn </td> 
 <td style="background-color:#f1f1f1;"> NOT IN 查询 </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> isNull </td> 
 <td style="vertical-align:top;"> NULL 值查询 </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> isNotNull </td> 
 <td style="background-color:#f1f1f1;"> IS NOT NULL </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> groupBy </td> 
 <td style="vertical-align:top;"> 分组 GROUP BY </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> having </td> 
 <td style="background-color:#f1f1f1;"> HAVING 关键词 </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> orderBy </td> 
 <td style="vertical-align:top;"> 排序 ORDER BY </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> orderAsc </td> 
 <td style="background-color:#f1f1f1;"> ASC 排序 ORDER BY </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> orderDesc </td> 
 <td style="vertical-align:top;"> DESC 排序 ORDER BY </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> exists </td> 
 <td style="background-color:#f1f1f1;"> EXISTS 条件语句 </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> notExists </td> 
 <td style="vertical-align:top;"> NOT EXISTS 条件语句 </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> between </td> 
 <td style="background-color:#f1f1f1;"> BETWEEN 条件语句 </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> notBetween </td> 
 <td style="vertical-align:top;"> NOT BETWEEN 条件语句 </td> 
 </tr> 
 <tr> 
 <td style="background-color:#f1f1f1;"> addFilter </td> 
 <td style="background-color:#f1f1f1;"> 自由拼接 SQL </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;"> last </td> 
 <td style="vertical-align:top;"> 拼接在最后，例如：last(“LIMIT 1”) </td> 
 </tr> 
 </tbody> 
</table>