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| 1 | +# 利用 Redis 列表实现页面数据分页 |
| 2 | + |
| 3 | +## 代码实现 |
| 4 | +| [Python](#Python-版本) | [Java](#Java-版本) | |
| 5 | +|---|---| |
| 6 | + |
| 7 | +### Python 版本 |
| 8 | +```python |
| 9 | +from redis import Redis |
| 10 | + |
| 11 | + |
| 12 | +class Paginate: |
| 13 | + def __init__(self, client: Redis, key: str): |
| 14 | + self.client = client |
| 15 | + self.key = key |
| 16 | + |
| 17 | + def add(self, item): |
| 18 | + """添加元素到分页列表中""" |
| 19 | + self.client.lpush(self.key, item) |
| 20 | + |
| 21 | + def get_page(self, page: int, per_page: int): |
| 22 | + """根据页码取出指定数量的元素""" |
| 23 | + start = (page - 1) * per_page |
| 24 | + end = page * per_page - 1 |
| 25 | + return self.client.lrange(self.key, start, end) |
| 26 | + |
| 27 | + def get_size(self): |
| 28 | + """获取列表的元素数量""" |
| 29 | + return self.client.llen(self.key) |
| 30 | + |
| 31 | + |
| 32 | +if __name__ == '__main__': |
| 33 | + redis = Redis(decode_responses=True) |
| 34 | + topics = Paginate(redis, 'user-topics') |
| 35 | + |
| 36 | + for i in range(24): |
| 37 | + topics.add(i) |
| 38 | + |
| 39 | + # 取总数 |
| 40 | + print(topics.get_size()) # 24 |
| 41 | + |
| 42 | + # 以每页5条数据的方式取出第1页数据 |
| 43 | + print(topics.get_page(1, 5)) # ['23', '22', '21', '20', '19'] |
| 44 | + |
| 45 | + # 以每页10条数据的方式取出第1页数据 |
| 46 | + print(topics.get_page(1, 10)) # ['23', '22', '21', '20', '19', '18', '17', '16', '15', '14'] |
| 47 | + |
| 48 | + # 以每页5条数据的方式取出第5页数据 |
| 49 | + print(topics.get_page(5, 5)) # ['3', '2', '1', '0'] |
| 50 | + |
| 51 | +``` |
| 52 | + |
| 53 | +### Java 版本 |
| 54 | +```java |
| 55 | +import redis.clients.jedis.Jedis; |
| 56 | + |
| 57 | +import java.util.List; |
| 58 | + |
| 59 | +public class Paginate { |
| 60 | + |
| 61 | + private Jedis client; |
| 62 | + private String key; |
| 63 | + |
| 64 | + public Paginate(Jedis client, String key) { |
| 65 | + this.client = client; |
| 66 | + this.key = key; |
| 67 | + } |
| 68 | + |
| 69 | + /** |
| 70 | + * 添加元素到分页列表中 |
| 71 | + * |
| 72 | + * @param item 元素 |
| 73 | + */ |
| 74 | + public void add(String item) { |
| 75 | + client.lpush(key, item); |
| 76 | + } |
| 77 | + |
| 78 | + /** |
| 79 | + * 根据页码取出指定数量的元素 |
| 80 | + * |
| 81 | + * @param page 页码 |
| 82 | + * @param pageSize 数量 |
| 83 | + * @return 元素列表 |
| 84 | + */ |
| 85 | + public List<String> getPage(int page, int pageSize) { |
| 86 | + long start = (page - 1) * pageSize; |
| 87 | + long end = page * pageSize - 1; |
| 88 | + return client.lrange(key, start, end); |
| 89 | + } |
| 90 | + |
| 91 | + /** |
| 92 | + * 获取列表的元素数量 |
| 93 | + * |
| 94 | + * @return 总数 |
| 95 | + */ |
| 96 | + public Long getTotalCount() { |
| 97 | + return client.llen(key); |
| 98 | + } |
| 99 | + |
| 100 | + public static void main(String[] args) { |
| 101 | + Jedis client = new Jedis(); |
| 102 | + Paginate topics = new Paginate(client, "user-topics"); |
| 103 | + for (int i = 0; i < 24; ++i) { |
| 104 | + topics.add(i + ""); |
| 105 | + } |
| 106 | + |
| 107 | + // 取总数 |
| 108 | + System.out.println(topics.getTotalCount()); // 24 |
| 109 | + |
| 110 | + // 以每页5条数据的方式取出第1页数据 |
| 111 | + System.out.println(topics.getPage(1, 5)); // [23, 22, 21, 20, 19] |
| 112 | + |
| 113 | + // 以每页10条数据的方式取出第1页数据 |
| 114 | + System.out.println(topics.getPage(1, 10)); // [23, 22, 21, 20, 19, 18, 17, 16, 15, 14] |
| 115 | + |
| 116 | + // 以每页5条数据的方式取出第5页数据 |
| 117 | + System.out.println(topics.getPage(5, 5)); // [3, 2, 1, 0] |
| 118 | + } |
| 119 | +} |
| 120 | +``` |
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