JMS Message components
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From: gk on 1 Jul 2010 00:22 http://download.oracle.com/docs/cd/E17477_01/javaee/5/api/javax/jms/Message.html JMS messages are composed of the following parts: Header - All messages support the same set of header fields. Header fields contain values used by both clients and providers to identify and route messages. Properties - Each message contains a built-in facility for supporting application-defined property values. Properties provide an efficient mechanism for supporting application-defined message filtering. Body - The JMS API defines several types of message body, which cover the majority of messaging styles currently in use. I don't understand the Properties section. It says .."Properties provide an efficient mechanism for supporting application-defined message filtering....". Could you please elaborate how it works the application-defined message filtering ? Is it something that Application ID is put into the Properties and receiver can find that whether message is intended for the receiver or not ? are they talking about this kind of filtering ?
From: Jean-Baptiste Nizet on 1 Jul 2010 03:53 On 1 juil, 06:22, gk <src...(a)gmail.com> wrote: > http://download.oracle.com/docs/cd/E17477_01/javaee/5/api/javax/jms/M... > > JMS messages are composed of the following parts: > > Header - All messages support the same set of header fields. Header > fields contain values used by both clients and providers to identify > and route messages. > > Properties - Each message contains a built-in facility for supporting > application-defined property values. Properties provide an efficient > mechanism for supporting application-defined message filtering. > > Body - The JMS API defines several types of message body, which cover > the majority of messaging styles currently in use. > > I don't understand the Properties section. It says .."Properties > provide an efficient mechanism for supporting application-defined > message filtering....". > > Could you please elaborate how it works the application-defined > message filtering ? Is it something that Application ID is put into > the Properties and receiver can find that whether message is intended > for the receiver or not ? are they talking about this kind of > filtering ? Yes they are. See http://download.oracle.com/docs/cd/E17477_01/javaee/5/tutorial/doc/bnceh.html#bncer and the section about selectors in http://download.oracle.com/docs/cd/E17477_01/javaee/5/api/javax/jms/Message..html To give you a concrete example on how it might be useful : the project I'm working on involves multiple servers listening on the same message queue. Multiple servers are needed to be able to sustain the load. Every message posted in the queue concerns one location, identified by a location code. And all the messages for a location must be handled sequentially. We thus have a listener on a first server listening for messages for locations A, B and C, while we have a second listener on the second server listening for messages for locations D, E and F. We do that by setting a property "locationCode" on each message posted in the queue. The first listener has the selector "locationCode IN ('A', 'B', 'C')", and the second one has the selector "locationCode IN ('D', 'E', 'F')". JB.
From: gk on 1 Jul 2010 04:36
On Jul 1, 12:53 pm, Jean-Baptiste Nizet <jni...(a)gmail.com> wrote: > On 1 juil, 06:22, gk <src...(a)gmail.com> wrote: > > > > > > >http://download.oracle.com/docs/cd/E17477_01/javaee/5/api/javax/jms/M... > > > JMS messages are composed of the following parts: > > > Header - All messages support the same set of header fields. Header > > fields contain values used by both clients and providers to identify > > and route messages. > > > Properties - Each message contains a built-in facility for supporting > > application-defined property values. Properties provide an efficient > > mechanism for supporting application-defined message filtering. > > > Body - The JMS API defines several types of message body, which cover > > the majority of messaging styles currently in use. > > > I don't understand the Properties section. It says .."Properties > > provide an efficient mechanism for supporting application-defined > > message filtering....". > > > Could you please elaborate how it works the application-defined > > message filtering ? Is it something that Application ID is put into > > the Properties and receiver can find that whether message is intended > > for the receiver or not ? are they talking about this kind of > > filtering ? > > Yes they are. > > Seehttp://download.oracle.com/docs/cd/E17477_01/javaee/5/tutorial/doc/bn.... > and the section about selectors inhttp://download.oracle.com/docs/cd/E17477_01/javaee/5/api/javax/jms/M... > > To give you a concrete example on how it might be useful : the project > I'm working on involves multiple servers listening on the same message > queue. Multiple servers are needed to be able to sustain the load. > Every message posted in the queue concerns one location, identified by > a location code. And all the messages for a location must be handled > sequentially. We thus have a listener on a first server listening for > messages for locations A, B and C, while we have a second listener on > the second server listening for messages for locations D, E and F. We > do that by setting a property "locationCode" on each message posted in > the queue. The first listener has the selector "locationCode IN ('A', > 'B', 'C')", and the second one has the selector "locationCode IN ('D', > 'E', 'F')". > very nice. I guess corelation ID also be an example of this then ? Anyway, you example was quite helpful. Thanks for your time and post. |