spring-data spring 的nosql的orm框架设计学习

1.spring-data-redis如何连接到redis服务端

其中定义了两个接口 org.springframework.data.redis.connection下的RedisConnection和RedisConnectionFactory工厂接口：

public interface RedisConnection extends RedisCommands {
void close() throws DataAccessException;

boolean isClosed();

Object getNativeConnection();

boolean isQueueing();

boolean isPipelined();

void openPipeline();

List<Object> closePipeline();
}

其中RedisCommands接口定义了redis支持的所有操作接口，

public interface RedisConnectionFactory extends PersistenceExceptionTranslator {

RedisConnection getConnection();
}

RedisConnectionFactory接口只定义一个获取连接的方法，而PersistenceExceptionTranslator定义了出现异常时把异常转化为spring通用的DataAccessException异常，可以供spring统一处理。

spring-data-redis通过三种方式连接：

Jedis connector

<bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory"
p:host-name="server" p:port="6379"/>

JRedis connector

<bean id="jredisConnectionFactory" class="org.springframework.data.redis.connection.jredis.JredisConnectionFactory"
p:host-name="server" p:port="6379"/>

RJC connector

<bean id="jredisConnectionFactory" class="org.springframework.data.redis.connection.rjc.RjcConnectionFactory" p:host-name="server" p:port="6379"/>

而spring-data-redis是统一通过RedisTemplate类给用户操作

<bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory"
p:use-pool="true"/>

<!-- redis template definition -->
<bean id="redisTemplate" class="org.springframework.data.redis.core.RedisTemplate"
p:connection-factory-ref="jedisConnectionFactory"/>

示例如下：

public class Example {

// inject the actual template
@Autowired
private RedisTemplate<String, String> template;

// inject the template as ListOperations
@Autowired
private ListOperations<String, String> listOps;

public void addLink(String userId, URL url) {
listOps.leftPush(userId, url.toExternalForm());
}
}

2.序列化

通过序列化接口org.springframework.data.redis.serializer来定制自己的序列化逻辑

public interface RedisSerializer<T> {
/**
* Serialize the given object to binary data.
*
* @param t object to serialize
* @return the equivalent binary data
*/
byte[] serialize(T t) throws SerializationException;

/**
* Deserialize an object from the given binary data.
*
* @param bytes object binary representation
* @return the equivalent object instance
*/
T deserialize(byte[] bytes) throws SerializationException;
}

存到redis上都是二进制的值，现在spring-data-redis里面已经提供了几种序列化机制：

JacksonJsonRedisSerializer json格式序列化

JdkSerializationRedisSerializer jdk的序列化

OxmSerializer spring的orm的序列化

StringRedisSerializer 简单的字符串跟字节转换序列化

3.spring-data-redis的消息发布订阅处理

<bean id="messageListener" class="org.springframework.data.redis.listener.adapter.MessageListenerAdapter">
<constructor-arg>
<bean class="redisexample.DefaultMessageDelegate"/>
</constructor-arg>
</bean>

<!-- and this is the message listener container... -->
<bean id="redisContainer" class="org.springframework.data.redis.listener.RedisMessageListenerContainer">
<property name="connectionFactory" ref="connectionFactory"/>
<property name="messageListeners">
<!-- map of listeners and their associated topics (channels or/and patterns) -->
<map>
<entry key-ref="messageListener">
<bean class="org.springframework.data.redis.listener.ChannelTopic">
<constructor-arg value="chatroom">
</bean>
</entry>
</map>
</property>
</bean>

每次接收到消息，就会调用注册的listener来处理。

4.支持spring cache的处理抽象

<bean id="cacheManager" class="org.springframework.data.redis.cache.RedisCacheManager" c:template-ref="redisTemplate">

这样支持在本地缓存访问过的记录。

5.访问redis时支持回调，给程序员开发充分的扩展性灵活性来处理自定义的一些操作

通过扩展回调接口：

public interface RedisCallback<T> {
/**
* Gets called by {@link RedisTemplate} with an active Redis connection. Does not need to care about activating or
* closing the connection or handling exceptions.
*
* @param connection active Redis connection
* @return a result object or {@code null} if none
* @throws DataAccessException
*/
T doInRedis(RedisConnection connection) throws DataAccessException;
}

实际上redisTemplate的所有操作都是通过这个回调接口来处理的

public List<Object> exec() {
return execute(new RedisCallback<List<Object>>() {

public List<Object> doInRedis(RedisConnection connection) throws DataAccessException {
return connection.exec();
}
});
}

public void delete(K key) {
final byte[] rawKey = rawKey(key);

execute(new RedisCallback<Object>() {

public Object doInRedis(RedisConnection connection) {
connection.del(rawKey);
return null;
}
}, true);
}

public void delete(Collection<K> keys) {
final byte[][] rawKeys = rawKeys(keys);

execute(new RedisCallback<Object>() {

public Object doInRedis(RedisConnection connection) {
connection.del(rawKeys);
return null;
}
}, true);
}

回调接口代码看起来很优雅，也非常灵活，设计得很不错。