List数据类型

List认识

总结官方

Redis lists are linked lists of string values. Redis lists are frequently used to:

• Implement stacks and queues.
• Build queue management for background worker systems. List的数据类型是一个双端链表实现方式，其中LPUSH从头添加元素，RPUSH从尾添加元素。即可以用List实现队列的使用。

Redis lists are implemented via Linked Lists. This means that even if you have millions of elements inside a list, the operation of adding a new element in the head or in the tail of the list is performed in constant time. The speed of adding a new element with the LPUSH command to the head of a list with ten elements is the same as adding an element to the head of list with 10 million elements. 官方说明了，甭管你是100w、100还是1000w,使用LPUSH和RPUSH速度相同（这不就是链表嘛），想想看链表的特性线性表

Lists are useful for a number of tasks, two very representative use cases are the following:

• Remember the latest updates posted by users into a social network.
• Communication between processes, using a consumer-producer pattern where the producer pushes items into a list, and a consumer (usually a worker) consumes those items and executes actions. Redis has special list commands to make this use case both more reliable and efficient.
  List常见的使用场景:
• 记住用户在社交网络中发布的最新更新
• 进程之间的通信，使用消费者-生产者模式，其中生产者将项目推送到列表中，消费者（通常是 Worker）消费这些项目并执行操作。 Redis 提供了特殊的列表命令，使这种用例更可靠、更高效。

同时官方给出例子:
The popular Twitter social network takes the latest tweets posted by users into Redis lists. To describe a common use case step by step, imagine your home page shows the latest photos published in a photo sharing social network and you want to speedup access.

• Every time a user posts a new photo, we add its ID into a list with LPUSH.
• When users visit the home page, we use LRANGE 0 9 in order to get the latest 10 posted items.

流行的 Twitter 社交网络会将用户发布的最新推文放入 Redis 列表中。 为了逐步描述一个常见的用例，想象一下你的主页会显示照片分享社交网络中发布的最新照片，而你希望加快访问速度。 每当用户发布一张新照片，我们就用 LPUSH 将其 ID 添加到一个列表中。 当用户访问主页时，我们使用 LRANGE 0 9 来获取最新发布的 10 张照片。

添加元素

PUSH命令

LPUSH 从左往右插入

LPUSH命令从头开始依次添加元素，先进的排在后面，后进的排在前面。留个谜底想想这是哪种数据结构的特性?

Redis Command

 127.0.0.1:6379> lpush list:user java vue python
 (integer) 3
 # 获取元素
 127.0.0.1:6379> lrange list:user 0 -1
 1) "python"
 2) "vue"
 3) "java"

Java

    // 第一种方式
    List<String> list = new ArrayList<>();
    list.add("水杯");
    list.add("保温杯");
    list.add("不锈钢杯");
    for (int i = 0; i < list.size(); i++) {
        redisTemplate.opsForList().leftPush("list:product",list.get(i));
    }   
    // 第二种方式
    redisTemplate.opsForList().leftPushAll("list:model","干饭","下地","锄禾日");
    // 第三种
    List<String> listF = new ArrayList<>();
    listF.add("水杯1");
    listF.add("保温杯2");
    listF.add("不锈钢杯");
    redisTemplate.opsForList().leftPushAll("list:feature",listF);

RPUSH 从右往左插入

RPUSH命令从尾开始依次添加元素，先进的排在前面，后进的排在后面。留个谜底想想这是哪种数据结构的特性?

Redis Command

 127.0.0.1:6379> rpush list:push money mone mon mo m
 (integer) 5
 127.0.0.1:6379> lrange list:push 0 -1
 1) "money"
 2) "mone"
 3) "mon"
 4) "mo"
 5) "m"
 127.0.0.1:6379>

Java

    // 第一种方式
    List<String> list = new ArrayList<>();
    list.add("水杯");
    list.add("保温杯");
    list.add("不锈钢杯");
    for (int i = 0; i < list.size(); i++) {
        redisTemplate.opsForList().rightPush("list:product",list.get(i));
    }   
    // 第二种方式
    redisTemplate.opsForList().rightPushAll("list:model","干饭","下地","锄禾日");
    // 第三种
    List<String> listF = new ArrayList<>();
    listF.add("水杯1");
    listF.add("保温杯2");
    listF.add("不锈钢杯");
    redisTemplate.opsForList().rightPushAll("list:feature",listF);

LINSERT 插入指定位置

LINSERT key <BEFORE | AFTER> pivot element
LINSERT命令就是在哪个元素前或者后添加一个新元素

Redis Command

 # 加 before 在mon前面加font
 127.0.0.1:6379> linsert list:push before mon font
 (integer) 5
 127.0.0.1:6379> lrange list:push 0 -1
 1) "money"
 2) "mone"
 3) "font"
 4) "mon"
 5) "mo"

Java

redisTemplate.opsForList().leftPush("list:push","font","code");

LRANGE 查询

LRANGE key start stop
LRANGE命令 查询数据使用，查询全部则 LRANGE key 0 -1

Redis Command

 # 查询0-3数据，也就是4个
 127.0.0.1:6379> lrange list:push 0 3
 1) "money"
 2) "mone"
 3) "font"
 4) "mon"

Java

redisTemplate.opsForList().range("list:model", 0, -1)

删除操作

RPOP 右删除

RPOP key [count]

Redis Command

 127.0.0.1:6379> rpop list:push
 "mo"

Java

redisTemplate.opsForList().rightPop("list:mode");

LPOP 左删除

LPOP key [count]

Redis Command

 127.0.0.1:6379> LPOP list:push
 "mo"

Java

redisTemplate.opsForList().leftPop("list:mode");

LLEN 元素个数

Redis Command

 127.0.0.1:6379> LLEN list:push
 5

Java

redisTemplate.opsForList().size("list:model")

LINDEX 根据下标查询元素

Redis Command

 127.0.0.1:6379> lindex list:push 2
 "font"

Java

redisTemplate.opsForList().index("list:model", 2)