RedisTemplate

1. Jedis与RedisTemplate的区别：
   Jedis是Redis官方推荐的面向Java的操作Redis的客户端，可以用JedisPool来获得连接进行get、set、del等操作相对简单，而RedisTemplate是SpringDataRedis中对JedisApi的高度封装。
   SpringDataRedis相对于Jedis来说可以方便地更换Redis的Java客户端，比Jedis多了自动管理连接池的特性，方便与其他Spring框架进行搭配使用如：SpringCache
   参考：https://blog.csdn.net/varyall/article/details/83476970

2. redisTemplate与stringRedisTemplate的区别
   第一点，StringRedisTemplate继承了RedisTemplate。
   第二点，RedisTemplate是一个泛型类，而StringRedisTemplate则不是。
   第三点，StringRedisTemplate只能对key=String，value=String的键值对进行操作，RedisTemplate可以对任何类型的key-value键值对操作。
   第四点，是他们各自序列化的方式不同，但最终都是得到了一个字节数组，殊途同归，StringRedisTemplate使用的是StringRedisSerializer类；RedisTemplate使用的是JdkSerializationRedisSerializer类。反序列化，则是一个得到String，一个得到Object
   这两个类是springboot-data-redis对Redis进行操作的实现类。

   打开StringRedisTemplate和RedisTemplate的源码，发现StringRedisTemplate继承了RedisTemplate，一般来说子类应该比父类有用更强大的功能，而此处却不是，因为RedisTemplate是泛型类，而在StringRedisTemplate继承RedisTemplate类时，则是指定了泛型的类型，两个String。
   这就直接导致了，StringRedisTemplate只能处理String-String的键值对数据，而RedisTemplate则可以处理任何类型的键值对。

RedisTemplate源码：

public class RedisTemplate extends RedisAccessor implements RedisOperations, BeanClassLoaderAware {}

StringRedisTemplate源码：

public class StringRedisTemplate extends RedisTemplate {}

参考：https://jingyan.baidu.com/article/f7ff0bfcc5c4152e26bb13bc.html

3. 序列化：
   redis中对序列化的应用主要是在四个方面，分别是
   keySerializer、valueSerializer、hashKeySerialiser、hashValueSerializer。可以从StringRedisTemplate的源码中体现出来：

/**
	 * Constructs a new StringRedisTemplate instance. {@link #setConnectionFactory(RedisConnectionFactory)}
	 * and {@link #afterPropertiesSet()} still need to be called.
	 */
	public StringRedisTemplate() {
		setKeySerializer(RedisSerializer.string());
		setValueSerializer(RedisSerializer.string());
		setHashKeySerializer(RedisSerializer.string());
		setHashValueSerializer(RedisSerializer.string());
	}

在redisTemplate中采用的序列化机制默认都是JdkSerializationRedisSerializer，源码：

	@Override
	public void afterPropertiesSet() {

		super.afterPropertiesSet();

		boolean defaultUsed = false;

		if (defaultSerializer == null) {

			defaultSerializer = new JdkSerializationRedisSerializer(
					classLoader != null ? classLoader : this.getClass().getClassLoader());
		}

		if (enableDefaultSerializer) {

			if (keySerializer == null) {
				keySerializer = defaultSerializer;
				defaultUsed = true;
			}
			if (valueSerializer == null) {
				valueSerializer = defaultSerializer;
				defaultUsed = true;
			}
			if (hashKeySerializer == null) {
				hashKeySerializer = defaultSerializer;
				defaultUsed = true;
			}
			if (hashValueSerializer == null) {
				hashValueSerializer = defaultSerializer;
				defaultUsed = true;
			}
		}

		if (enableDefaultSerializer && defaultUsed) {
			Assert.notNull(defaultSerializer, "default serializer null and not all serializers initialized");
		}

		if (scriptExecutor == null) {
			this.scriptExecutor = new DefaultScriptExecutor<>(this);
		}

		initialized = true;
	}

而在StringRedisTemplate中默认采用的序列化机制是：StringRedisSerializer，源码：

/**
	 * Constructs a new StringRedisTemplate instance. {@link #setConnectionFactory(RedisConnectionFactory)}
	 * and {@link #afterPropertiesSet()} still need to be called.
	 */
	public StringRedisTemplate() {
		setKeySerializer(RedisSerializer.string());
		setValueSerializer(RedisSerializer.string());
		setHashKeySerializer(RedisSerializer.string());
		setHashValueSerializer(RedisSerializer.string());
	}
/**
	 * Obtain a simple {@link java.lang.String} to {@literal byte[]} (and back) serializer using
	 * {@link java.nio.charset.StandardCharsets#UTF_8 UTF-8} as the default {@link java.nio.charset.Charset}.
	 *
	 * @return never {@literal null}.
	 * @since 2.1
	 */
	static RedisSerializer string() {
		return StringRedisSerializer.UTF_8;
	}
	public static final StringRedisSerializer UTF_8 = new StringRedisSerializer(StandardCharsets.UTF_8);

无论是JdkSerializationRedisSerializer还是StringRedisSerializer都实现泛型接口RedisSerializer, 源码：

/**
 * Basic interface serialization and deserialization of Objects to byte arrays (binary data). It is recommended that
 * implementations are designed to handle null objects/empty arrays on serialization and deserialization side. Note that
 * Redis does not accept null keys or values but can return null replies (for non existing keys).
 *
 * @author Mark Pollack
 * @author Costin Leau
 * @author Christoph Strobl
 */
public interface RedisSerializer {}

/**
 * Java Serialization Redis serializer. Delegates to the default (Java based) {@link DefaultSerializer serializer} and
 * {@link DefaultDeserializer}. This {@link RedisSerializer serializer} can be constructed with either custom
 * {@link ClassLoader} or own {@link Converter converters}.
 *
 * @author Mark Pollack
 * @author Costin Leau
 * @author Mark Paluch
 * @author Christoph Strobl
 */
public class JdkSerializationRedisSerializer implements RedisSerializer