I'll copy my question here - in case there are other experts who are not on
the users group. I guess bad timing on my part.
All,
Just wondering - can we complement this with a method along the lines of
"isPayloadType(Class<?> clazz)" that returns true if the underlying payload
can be cast to the given class, false if it cannot be (or if it's a stream
message?)
I know in my applications today I have up to three if blocks depending on
the message implementation used, and would need this logic to check before
processing. It may also be cleaner than catching the exception.
John
On Tue, Oct 23, 2012 at 7:29 AM, Nigel Deakin <nigel.deakin_at_oracle.com>wrote:
> Following Pete's proposal (and Chris's support) I have logged this JIRA
> issue:
>
> http://java.net/jira/browse/**JMS_SPEC-101<http://java.net/jira/browse/JMS_SPEC-101>
> New method Message.getPayload(Class<T> c)
>
> Please indicate whether you support adding this new method to JMS 2.0.
>
> This is a proposal to add a new method to javax.jms.Message which allows
> the message payload to be obtained without the need to cast the object to
> the appropriate subtype first. This can slightly simplify the code of a
> MessageListener's, onMessage method, where the object passed in is always
> declared to be a javax.jms.Message.
>
> Here is the proposed API:
>
> /**
> * Returns the messages's payload, which must be of the specified
> type. If
> * the message has no payload then null is returned. This method
> may be used
> * to obtain the payload of any type of message except for
> * <tt>StreamMessage</tt>.
> * * @param c
> * The class of the payload.<br/>
> * If the message is a <code>TextMessage</code> then
> this should
> * be set to <code>String.class</code>.<br/**>
> * If the message is a <code>ObjectMessage</code> then
> this
> * should be set to <code>java.io.Serializable.**class</code>.
> <br/>
> * If the message is a <code>MapMessage</code> then
> this should
> * be set to <code>java.util.Map.class</**code>.<br/>
> * If the message is a <code>BytesMessage</code> then
> this should
> * be set to <code>byte[].class</code>.<br/**>
> * If the message payload is not of the specified type a
> * <code>MessageFormatException</**code> will be thrown
> * * @return the messages's payload
> * * @exception JMSException
> * if the JMS provider fails to get the payload due
> to some
> * internal error.
> * @exception MessageFormatException
> * if the payload is not of the specified type or,
> if the
> * message is an ObjectMessage, if object
> deserialization
> * fails.
> * @Exception MessageNotReadableException - if the message is a
> BytesMessage
> * and the message is in write-only mode.
> */
> <T> T getPayload(Class<T> c) throws JMSException;
>
> This means that instead of something like:
>
> public void onMessage(Message message) {
> String payload = ((TextMessage) message).getText();
>
> we could have
>
> public void onMessage(Message message) {
> String payload2 = message.getPayload(String.**class);
>
>
>
>