[置顶] 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。