51工具盒子作为一个人，对父母要尊敬，对子女要慈爱，对穷亲戚要慷慨，对一切人要有礼貌。------(美国)罗素
都封装好了
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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 | hljs java /** * 随机取几条 * * @param function 表名::列名 * @return T * @author <achao1441470436@gmail.com> * @since 2021/5/17 0017 10:34 */ @SuppressWarnings("unchecked") public static <T, O> List<O> getAny(SFunction<O, T> function, Integer limit) { SerializedLambda lambda = Optional.ofNullable(function).map(LambdaUtils::resolve).orElseThrow(() -> ExceptionUtils.mpe("传入条件不能为空")); Class<O> entityClass = (Class<O>) lambda.getImplClass(); TableInfo tableInfo = Optional.ofNullable(entityClass).map(TableInfoHelper::getTableInfo).orElseThrow(() -> ExceptionUtils.mpe("未找到该实体类对应BaseMapper，请注入对应mybatis-plus的BaseMapper")); String tableName = tableInfo.getTableName(); String id = PropertyNamer.methodToProperty(lambda.getImplMethodName()); List<HashMap<String, Object>> mapList = (List<HashMap<String, Object>>) USER_MAPPER.getAny(tableName, id, limit, entityClass); List<TableFieldInfo> fieldList = tableInfo.getFieldList(); Reflector reflector = new Reflector(entityClass); Map<String, Invoker> columnSetterMap = fieldList.parallelStream().collect(Collectors.toMap(tbf -> Optional.ofNullable(tbf).map(TableFieldInfo::getField).map(field -> field.getAnnotation(TableField.class)).map(TableField::value).filter(StringUtils::isNotBlank).orElse(Objects.requireNonNull(tbf).getProperty()), f -> reflector.getSetInvoker(f.getProperty()), (v1, v2) -> v2)); return mapList.stream().map(map -> { O bean = ClassUtils.newInstance(entityClass); map.forEach((key, value) -> Optional.ofNullable(key).map(columnSetterMap::get).ifPresent(i -> { try { i.invoke(bean, new Object[]{value}); } catch (IllegalAccessException | InvocationTargetException e) { e.printStackTrace(); } })); return bean; }).collect(Collectors.toList()); } /** * 随机取一条 * * @param function 表名::列名 * @return O 随便取的 * @author <achao1441470436@gmail.com> * @since 2021/5/17 0017 12:29 */ public static <O> O getAnyOne(SFunction<O, ?> function) { return getAny(function, 1).parallelStream().findAny().orElse(null); } |
这里的USER_MAPPER我们可以使用任意一个mapper，我这里使用的是静态注入的方式
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| 1 | hljs java private static final UserMapper USER_MAPPER = SpringContextHolder.getBean(UserMapper.class); |
然后是mapper里的方法
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| 1 2 3 4 5 6 7 8 9 10 11 | hljs java /** * 随机取一条 * * @param tableName 表名 * @param columnName 列名 * @param limit 取几条 * @return O * @author <achao1441470436@gmail.com> * @since 2021/5/17 0017 10:47 */ <O> List<O> getAny(@Param("table_name") String tableName, @Param("id") String columnName, @Param("limit") Integer limit, Class<O> type); |
以及对应的xml
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| 1 2 3 4 5 6 7 | hljs xml <!-- 随机取一条 --> <select id="getAny" resultType="java.util.Map"> SELECT * FROM ${table_name} AS t1 JOIN (SELECT ROUND(RAND() *((SELECT MAX(${id}) FROM ${table_name}) - (SELECT MIN(${id}) FROM ${table_name})) +(SELECT MIN(${id}) FROM ${table_name})) AS tmp_id) AS t2 WHERE t1.${id} >= t2.tmp_id ORDER BY t1.${id} LIMIT #{limit}; </select> |
实际使用场景、方式
