分批查询工具类

BatchQueryUtil.java

    /**
     * 分批查询
     *
     * <p>
     * sql中copy以下代码：
     * <pre>{@code
     *  <if test="begin != null and pageSize != null">
     *      limit #{begin}, #{pageSize}
     *  </if>
     * }</pre>
     *
     * @param batchQueryListFunction mapper查询方法
     * @param paramMap               paramMap 查询参数map
     * @param pageSize               pageSize 每批次大小
     * @return 查询结果合集
     */
    public static <E> List<E> batchQuery(Function<Map<String, Object>, List<E>> batchQueryListFunction, Map<String, Object> paramMap, int pageSize) {
        List<E> allList = new ArrayList<>();
        int page = 0;
        HashMap<String, Object> newParamMap;
        if (paramMap == null) {
            newParamMap = new HashMap<>(2);
        } else {
            newParamMap = new HashMap<>(paramMap);
        }
        newParamMap.put("pageSize", pageSize);
        for (; ; ) {
            newParamMap.put("begin", page * pageSize);
            List<E> splitList = batchQueryListFunction.apply(newParamMap);
            // 第一次查询结果为空
            if (page == 0 && CollectionUtils.isEmpty(splitList)) {
                return Collections.emptyList();
            }
            if (CollectionUtils.isNotEmpty(splitList)) {
                allList.addAll(splitList);
            }
            if (splitList.size() < pageSize) {
                break;
            }
            page++;
        }
        return allList;
    }

    /**
     * 分批查询；默认每批次查500
     *
     * <p>
     * sql中copy以下代码：
     * <pre>{@code
     *  <if test="begin != null and pageSize != null">
     *      limit #{begin}, #{pageSize}
     *  </if>
     * }</pre>
     *
     * @param batchQueryListFunction mapper查询方法
     * @param paramMap               paramMap 查询参数map
     * @return 查询结果合集
     */
    public static <E> List<E> batchQuery(Function<Map<String, Object>, List<E>> batchQueryListFunction, Map<String, Object> paramMap) {
        return batchQuery(batchQueryListFunction, paramMap, 500);
    }