Spring提供了一个消息的封装接口MessageConverter,我们需要自行去实现它,从而完成消息的定义,封装.
public Message toMessage(Object obj, Session session) throws JMSException,
MessageConversionException
public Object fromMessage(Message msg) throws JMSException,
MessageConversionException
toMessage 提供了一个消息打包的调用,Spring会在jmstemplate调用template.convertAndSend(this.destination, order);的时候 调用toMessage方法
同时,会在MessageListenerAdapter收到原始的jms消息后,首先调用formMessage,然后把消息解包成普通对象,作为参数再返给OrderMessageConsumer的sendEmail方法
SS2中,在convert中使用的是ActiveMQObjectMessage来封装消息。具体代码参见OrderMessageConvert
ActiveMQObjectMessage 这里需要注意的是如果你使用的是setObjectProperty(String key,Object value),那么这里的value要不然是Strings 或者是 primitive类型,要不然就只能是map或者list。这里还有要说明的是,如果你使用embedded-vm(未使用持久化)的时候,即使你的Order,OrderItem,Product未实现Serialzable接口,也不会报错,但是一旦你的broker配置了持久化或者是远程broker或者使用其他的transport协议的时候,就会提示Order is not primitive type,因此在springside2 最新的版本中,OrderMessageConver的包装形式已经作了修改,会将Order序列化成byte然后发送。也就是我们可以将消息的定义在Conver完成,而对于上层业务来说是透明的,如果你不想Order,OrderItem,Product实现Serializable接口,那么你就需要在Convert作其他的封装用来发送消息.
JMS provides five forms of message body. Each form is defined by a message nterface:
• StreamMessage - a message whose body contains a stream of Java primitive values. It is filled and read sequentially.
• MapMessage - a message whose body contains a set of name-value pairs where names are Strings and values are Java primitive types. The entries can be accessed sequentially by enumerator or randomly by name. The order of the entries is undefined.
• TextMessage - a message whose body contains a java.lang.String. The inclusion of this message type is based on our presumption that String messages will be used extensively. One reason for this is that XML will likely become a popular mechanism for representing the content of JMS messages.
• ObjectMessage - a message that contains a Serializable Java object. If a collection of Java objects is needed, one of the collection classes provided in JDK 1.2 can be used.
• BytesMessage - a message that contains a stream of uninterpreted bytes.This message type is for literally encoding a body to match an existing message format. In many cases, it will be possible to use one of the other,self-defining, message types instead. Although JMS allows the use of message properties with byte messages, they are typically not used, since the inclusion of properties may affect the format.
