Simple operations for redis caching (get put)

This article describes simple redis caching operations, including introducing the jedisjar package, configuring redis, RedisDao, putting data into redis (put), fetching data from redis (get), and accessing redis logic

1. Introduce the jedis jar package

<!-- java access redis the jar package jedis -->
<dependency>
 <groupId>redis.clients</groupId>
 <artifactId>jedis</artifactId>
 <version>2.7.3</version>
</dependency>
<!-- protostuff Serialization dependency  -->
<dependency>
 <groupId>com.dyuproject.protostuff</groupId>
 <artifactId>protostuff-core</artifactId>
 <version>1.0.8</version>
</dependency>
<dependency>
 <groupId>com.dyuproject.protostuff</groupId>
 <artifactId>protostuff-runtime</artifactId>
 <version>1.0.8</version>
</dependency>

Note: why introduce the serialization dependency jar package protostuff?

1) the data extracted from redis is serialized. We need to use the deserialization operation of protostuff to convert the serialized object into the object we need

2) when putting data into redis, we need to use the serialization operation of protostuff to convert the object into a serialized object before putting into redis

2. Inject redis into the spring configuration file and put it into the ioc container of spring

<!--  injection redis dao -->
<bean id="redisDao" class="org.demo.dao.cache.RedisDao">
　　<constructor-arg index="0" value="localhost"></constructor-arg>
　　<constructor-arg index="1" value="6379"></constructor-arg>
</bean>

Note:

1) the RedisDao path here is my package path, note that you should use your own path when configuring

2) local redis service localhost is used here

3) the default port of redis service is 6379

3. RedisDao needs some tools

//redis The connection pool 
 private final JedisPool jedisPool;// Generates an empty object based on the object's bytecode file 
 private RuntimeSchema<Object> schema = RuntimeSchema.createFrom(Object.class); //Object.class : gets the bytecode of the object 
 
 public RedisDao(String ip, int port){
  jedisPool = new JedisPool(ip, port);
 }

Note:

1) RedisDao requires redis's connection pool JedisPool, just like JDBC's database connection pool 1. We will initialize the connection pool in RedisDao's constructor

2) we need a tool RuntimeSchema that can generate empty objects according to the object's bytecode file. Whatever object you want to use, you write to your object at Object (Object.class: get the object's bytecode file)

3) the initialization of connection pool JedisPool requires two parameters: ip and port

4. Put data into redis (put)

// Cache the object into redis
 public String putObject(Object obj){
  // Caching logic :Object -->  serialization  --> byte[] -->  The cache to redis
  try {
   Jedis jedis = jedisPool.getResource(); // To obtain redis The connection object is equivalent to JDBC the connection
   try{
    String key = "Object:"+obj.getId();
    // serialize 
    byte[] bytes = ProtostuffIOUtil.toByteArray(seckill, schema, 
      LinkedBuffer.allocate(LinkedBuffer.DEFAULT_BUFFER_SIZE)); // If the object is too large, it is buffered 
    // Start the cache 
    int timeout = 60*60; // Set timeout time  1 hours , Through timeout maintenance 1 consistency 
    String result = jedis.setex(key.getBytes(), timeout, bytes);
    return result;
   }finally{
    jedis.close();
   }
  } catch (Exception e) {
   e.printStack();
  }
  return null;
 }

Note:

1) cache logic: Object -- > Serialization operation -- > byte[] -- > Write redis. That means serializing the object first, and then writing redis!

2) we must get the connection object of redis from the connection pool before operating redis

5. Data from redis (get)

 // from redis Query in cache 
 public Object getObject(long id){
  //redis Operation logic 
  try {
   Jedis jedis = jedisPool.getResource(); // Cache connection objects, equivalent to database connection objects connection
   try {
    String key = "Object:"+id;
    // The entity object does not implement an internal serialization operation 
    // Cache logic: getByte[] -->  deserialization  --> Object
    byte[] bytes = jedis.get(key.getBytes()); // from jedis Gets an array of serialized objects for the target object 
    if(bytes != null){
     // Deserialization logic 
     Object obj = schema.newMessage(); // through schema generate 1 Two new empty objects 
     ProtostuffIOUtil.mergeFrom(bytes, obj, schema); // Do the deserialization operation 
     return obj;
    }
    
   } finally {
    jedis.close();
   }
    
  } catch (Exception e) {
　　　　　　　　e.printStack();
  }
  return null;
 }

Note:

1) data fetching logic: redis -- > Get byte - [] > Deserialization -- > Object

2) when we put the data, it is in the form of key-value pairs: id -- > obj. When we fetch data, we fetch it according to id

6. Logic when querying redis

Pseudo code:

get form redis_cache    // The first query redis
if null       // If there is no 
 get from db     // From the database db The query 
 if null      // If it still doesn't 
  return null    // So return null 
 else       // Otherwise, 
  put into redis_cache  // Now put the data in redis
  return obj    // Put the data back 
else        // If from redis Found in 
 return obj     // So just return the data