springboot默认是使用基于lettuce的redis客户端，默认情况下LettuceConnectionFactory的shareNativeConnection属性值为true；在springboot的IOC容器之中一个LettuceConnectionFactory最多提供两个共享本地连接，一个给RedisTemplate和StringRedisTemplate的所有操作共用，另外一个给ReactiveRedisTemplate和ReactiveStringRedisTemplate的所有操作共用。

一个对springboot redis框架进行重写，支持lettuce、jedis、连接池、同时连接多个集群、多个redis数据库、开发自定义属性配置的开源SDK：

<dependency><groupId>io.github.mingyang66</groupId><artifactId>emily-spring-boot-redis</artifactId><version>4.3.9</version>
</dependency>

GitHub地址：https://github.com/mingyang66/spring-parent

一、LettuceConnectionFactory连接工厂类默认属性

	//建立Redis连接的client对象private @Nullable AbstractRedisClient client;private @Nullable LettuceConnectionProvider connectionProvider;private @Nullable LettuceConnectionProvider reactiveConnectionProvider;//是否校验连接，默认：falseprivate boolean validateConnection = false;//是否共享本地连接，默认：trueprivate boolean shareNativeConnection = true;//是否提前初始化共享本地连接，默认：falseprivate boolean eagerInitialization = false;//通用共享本地连接，默认：nullprivate @Nullable SharedConnection<byte[]> connection;//基于reactive的通用共享本地连接，默认：nullprivate @Nullable SharedConnection<ByteBuffer> reactiveConnection;

二、Redis连接获取统一入口RedisConnectionUtils#doGetConnection

public static RedisConnection doGetConnection(RedisConnectionFactory factory, boolean allowCreate, boolean bind,boolean transactionSupport) {...//入参factory是LettuceConnectionFactory对象，RedisConnection connection = fetchConnection(factory);...return connection;}private static RedisConnection fetchConnection(RedisConnectionFactory factory) {//通过LettuceConnectionFactory对象的getConnection方法获取连接对象return factory.getConnection();}

三、LettuceConnectionFactory#getConnection连接工厂类方法获取连接对象

	public RedisConnection getConnection() {assertInitialized();if (isClusterAware()) {return getClusterConnection();}//此处会获取基于lettuce的连接对象LettuceConnection connection = doCreateLettuceConnection(getSharedConnection(), connectionProvider, getTimeout(),getDatabase());connection.setConvertPipelineAndTxResults(convertPipelineAndTxResults);return connection;}// 当前shareNativeConnection为true,则回去获取或者创建本地原生共享连接@Nullableprotected StatefulRedisConnection<byte[], byte[]> getSharedConnection() {return shareNativeConnection && !isClusterAware()? (StatefulRedisConnection) getOrCreateSharedConnection().getConnection(): null;}// 首先创建一个共享连接对象，此处包含一个真实创建连接对象的connectionProvider对象，实际是StandaloneConnectionProvider// 实际的创建原理，我们后面的文章分析private SharedConnection<byte[]> getOrCreateSharedConnection() {synchronized (this.connectionMonitor) {if (this.connection == null) {this.connection = new SharedConnection<>(connectionProvider);}return this.connection;}}

四、LettuceConnectionFactory.SharedConnection#getConnection创建原生共享本地连接

		// 此方法是所有创建真正的物理连接都要调用的方法入口@NullableStatefulConnection<E, E> getConnection() {synchronized (this.connectionMonitor) {//如果连接不存在，则会创建本地连接if (this.connection == null) {this.connection = getNativeConnection();}// 此处是根据属性配置是否需要校验连接有效性，如果需要则会校验，本文不做重点分析if (getValidateConnection()) {validateConnection();}return this.connection;}}private StatefulConnection<E, E> getNativeConnection() {//此处是创建本地连接的入口，具体是调用LettuceConnectionProvider的子类StandaloneConnectionProviderreturn connectionProvider.getConnection(StatefulConnection.class);}

五、StandaloneConnectionProvider#getConnection方法创建本地连接

	@Overridepublic <T extends StatefulConnection<?, ?>> T getConnection(Class<T> connectionType) {if (connectionType.equals(StatefulRedisSentinelConnection.class)) {return connectionType.cast(client.connectSentinel());}if (connectionType.equals(StatefulRedisPubSubConnection.class)) {return connectionType.cast(client.connectPubSub(codec));}//本地连接是通过此处方法创建，具体是通过client.connect创建//此处的client是通过LettuceConnectionFactory的afterPropertiesSet方法初始化的client对象//再具体的创建连接过程要进入RedisClient对象中，本文不做进一步分析。if (StatefulConnection.class.isAssignableFrom(connectionType)) {return connectionType.cast(readFrom.map(it -> this.masterReplicaConnection(redisURISupplier.get(), it)).orElseGet(() -> client.connect(codec)));}throw new UnsupportedOperationException("Connection type " + connectionType + " not supported");}

六、共享本地连接是如何实现的

​ 经过上面的源码分析其实结果已经很清楚了，redis的共享本地连接就保存在ioc容器中的LettuceConnectionFactory连接工厂类对象中，有两个属性connection、reactiveConnection，其为通用编程模式和响应式编程分别提供了一个共享本地对象，开发者可以根据个人编程需求通过RedisTemplate等模板对象去LettuceConnectionFactory对象上去取符合要求的共享本地连接。