Springboot+Redis executes lua script

With the wide application of Redis database, its role in server-side applications is becoming more and more important. Redis has many features such as fast reading and writing, data persistence, publishing and subscription, and transaction processing. These features make it excellent in handling high concurrency and real-time data operations. However, simply using Redis is not enough to meet the needs of some complex business logic. In this case, Lua scripts become an important complement to Redis. This article will introduce in detail the combined application of Redis and Lua scripts.

1. Redis overview

Redis is an in-memory data storage system that supports a variety of data structures, such as strings, hash tables, lists, sets, and ordered sets. Redis has the advantages of high performance, scalability and reliability, and is widely used in cache, message queue, real-time data analysis and other fields.

2. Introduction to Lua script

Lua is a lightweight, embeddable scripting language that is widely used in game development, embedded systems and other fields. Lua has the advantages of concise syntax, strong readability, and easy learning, and supports both process-oriented and object-oriented programming styles.

In Redis, Lua scripts can be used to execute some complex business logic, such as atomic transaction operations, conditional queries, etc. Through Lua scripts, we can implement some complex logic directly in Redis without the need for transfer through external programs.

3. Benefits of combining Redis and Lua scripts:

Efficiency: By using Lua scripts, multiple Redis commands can be combined together and executed in one request, thereby reducing network overhead and latency.
Reliability: Lua scripts can ensure the atomicity of operations and avoid errors or conflicts that may occur during the execution of multiple commands.
Reusability: By storing scripts in Redis and being reused by other clients, you can avoid writing the same code repeatedly.
Convenience: Complex business logic can be easily implemented using Lua scripts, and data can be shared between the client and server.
Embeddability: Lua scripts can be embedded into Redis servers, allowing interaction with Redis through programming languages.

4. Redis eval command

The EVAL command of Redis is a command used to execute Lua scripts. It allows Lua scripts to be passed to Redis as strings and executed by Redis's Lua interpreter. The basic syntax of the EVAL command is as follows:

EVAL script numkeys key [key ...] arg [arg ...]

in:

script: Lua script to be executed.
numkeys: The number of key parameters passed to the Lua script.
key [key ...]: Key parameters passed to the Lua script, separated by commas.
arg [arg ...]: Additional parameters passed to the Lua script, separated by commas.

example:

EVAL "return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}" 2 key1 key2 first second
1) "key1"
2) "key2"
3) "first"
4) "second"

5. Execute redis command in Lua

In Lua scripts, you can use Redis commands to perform various operations. Here are some examples of commonly used Redis commands:

1.Set and get values

local key = "mykey"  
local value = "myvalue"  
redis.call("SET", key, value) -- 设置键值对  
local retrievedValue = redis.call("GET", key) -- 获取键的值

2. List operations

local listKey = "mylist"  
redis.call("LPUSH", listKey, "item1") -- 在列表头部插入元素  
redis.call("RPUSH", listKey, "item2") -- 在列表尾部插入元素  
local leftValue = redis.call("LPOP", listKey) -- 从列表头部弹出元素  
local rightValue = redis.call("RPOP", listKey) -- 从列表尾部弹出元素

3. Collection operation

local setKey = "myset"  
redis.call("SADD", setKey, "item1") -- 添加元素到集合  
redis.call("SADD", setKey, "item2")  
local isMember = redis.call("SISMEMBER", setKey, "item1") -- 检查元素是否在集合中

4. Transaction operations

redis.call("MULTI") -- 开始事务块  
redis.call("SET", "key1", "value1")  
redis.call("SET", "key2", "value2")  
local result = redis.call("EXEC") -- 执行事务块

These are some commonly used command examples in Redis. You can use other commands to perform more complex operations as needed. Please note that Redis command calls in Lua scripts are redis.callmade through functions.

6. Springboot combines with redis to implement Lua script operations

6.1. Springboot integrates redis

Add the Redis dependency to your pom.xmlfile:

<dependency>  
    <groupId>org.springframework.boot</groupId>  
    <artifactId>spring-boot-starter-data-redis</artifactId>  
</dependency>

2. Configure Redis connection parameters in the application.propertiesor file:application.yml

spring.redis.host=localhost  
spring.redis.port=6379

3. Use StringRedisTemplateor RedisTemplateto execute Lua script

First we need to initialize the member variables:

  //lua脚本
    private DefaultRedisScript<Boolean> casScript;

    @Resource
    private RedisTemplate redisTemplate;
    @PostConstruct
    public void init(){
        casScript=new DefaultRedisScript<>();
        //lua脚本类型
        casScript.setResultType(Boolean.class);
        //lua脚本在哪加载
        casScript.setScriptSource(new ResourceScriptSource(new ClassPathResource("compareAndSet.lua")));
    }

use:

    public Boolean compareAndSet(String key,Long oldValue,Long newValue){
        List<String> keys=new ArrayList<>();
        keys.add(key);
        //参数一为lua脚本   
        //参数二为keys集合    对应KEYS[1]、KEYS[2]....
        //参数三为可变长参数  对应 ARGV[1]、ARGV[2]...
        return (Boolean) redisTemplate.execute(casScript,keys,oldValue,newValue);
    }

6.2. Use lua script to implement cas operation

initialization:

 @Resource
    private RedisTemplate redisTemplate;
    //lua脚本
    private DefaultRedisScript<Boolean> casScript;
    @PostConstruct
    public void init(){
        casScript=new DefaultRedisScript<>();
        //lua脚本类型
        casScript.setResultType(Boolean.class);
        //lua脚本在哪加载
        casScript.setScriptSource(new ResourceScriptSource(new ClassPathResource("compareAndSet.lua")));
    }
    public Boolean compareAndSet(String key,Long oldValue,Long newValue){
        List<String> keys=new ArrayList<>();
        keys.add(key);
        return (Boolean) redisTemplate.execute(casScript,keys,oldValue,newValue);
    }

lua script:

local key=KEYS[1]
local oldValue=ARGV[1]
local newValue=ARGV[2]
local redisValue=redis.call('get',key)
if(redisValue==false or tonumber(redisValue)==tonumber(oldValue))
then
    redis.call('set',key,newValue)
    return true
else
    return false
end

use:

  public Boolean compareAndSet(String key,Long oldValue,Long newValue){
        List<String> keys=new ArrayList<>();
        keys.add(key);
        return (Boolean) redisTemplate.execute(casScript,keys,oldValue,newValue);
    }

Summarize

In this article, we introduced how to use Redis to execute Lua scripts in Spring Boot. By combining Lua scripts and Redis, we can implement complex business logic, improve the atomicity and execution efficiency of operations, and reduce network communication overhead.

However, there are a few things to note when using Lua scripts:

Ensure the correctness and security of Lua scripts to avoid injection attacks and other security issues.
When executing Lua scripts, you need to carefully handle possible exceptions and ensure the stability of the script.
When using Lua scripts, you need to consider network latency and the performance of the Redis server to avoid excessive load on the Redis server.

In short, Spring Boot combined with Redis and Lua scripts can provide us with more powerful and flexible data processing capabilities, but we need to pay attention to security and performance issues. In practical applications, trade-offs and choices need to be made based on specific circumstances.