I think everyone who wishes to comment on this proposal has now made their views known.
There seems to be general support for the new method Message.getBody(Class<T> c). Encouraging comments were received
from John A, Rob, Clebert, Chris. So I'm now going to add it to the spec.
There was less clear support for Message.isBodyAssignableTo(Class<T> c), though those who criticised it were more
concerned that it was not useful then that it was bad or invalid. My feeling is that it is forms a potentially-useful
companion to getBody and worth keeping. Since it is easy to specify and implement I've decided to keep it, at least for now.
Thank you to everyone for your comments - and to Pete Muir for first suggesting it.
Nigel
On 26/10/2012 15:00, Nigel Deakin wrote:
> http://java.net/jira/browse/JMS_SPEC-101
> New method Message.getBody(Class<T> c)
>
> Following preceding discussions, I have changed the name of this method to getBody and polished the javadoc comment
> slightly. The updated API doc can be seen below and also at
> http://jms-spec.java.net/2.0-SNAPSHOT/apidocs/javax/jms/Message.html#getBody%28java.lang.Class%29
>
> In addition, I have taken up John A's suggestion and drafted an API doc for a method isBodyAssignableTo which can be
> used to find out whether a subsequent call to getBody would fail because of an incompatible type. The APi docs can be
> seen below and also at
> http://jms-spec.java.net/2.0-SNAPSHOT/apidocs/javax/jms/Message.html#isBodyAssignableTo%28java.lang.Class%29
>
> I think getBody() would be a nice addition to the API and is a useful complement to the new receivePayload methods. It
> would remove the need to cast a Message to a specific subtype in other cases such as in a MessageListener. However I
> would still welcome your views on this.
>
> I am less sure about isBodyAssignableTo. It is simple enough to define, but I'm not totally convinced there's a good
> case for adding it. Is this a useful complement to getBody, or is it simply bloat?
>
> So please express your views on the following:
>
> 1. Do you support the addition of Message.getBody() as defined below?
>
> 2. Do you support the addition of Message.isBodyAssignableTo() as defined below?
>
> Thanks,
>
> Nigel
>
> Here are those javadocs:
>
>
> /**
> * Returns the message body as an object of the specified type. The message
> * body must be capable of being assigned to the specified type. This means
> * that the specified class or interface must be either the same as, or a
> * superclass or superinterface of, the class of the message body. This
> * method may be used to obtain the body of any type of message except for
> * <tt>StreamMessage</tt>. If the message has no body then null is returned.
> *
> * @param c
> * The type to which the message body should be assigned. <br/>
> * If the message is a <code>TextMessage</code> then this should
> * be set to <code>String.class</code> or another class to which
> * a String is assignable. <br/>
> * If the message is a <code>ObjectMessage</code> then this
> * should be set to <code>java.io.Serializable.class</code> or
> * another class to which the payload is assignable. <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>. The
> * <code>BytesMessage</code> must not be in write-only mode.
> *
> * @return the message body
> *
> * @exception JMSException
> * if the JMS provider fails to get the message body due to
> * some internal error.
> * @exception MessageFormatException
> * if the message is a <code>StreamMessage</code>, or the
> * message body cannot be assigned to the specified type, or
> * the message is an <code>ObjectMessage</code> and object
> * deserialization fails.
> * @exception MessageNotReadableException
> * if the message is a <code>BytesMessage</code> and the
> * message is in write-only mode.
> */
> <T> T getBody(Class<T> c) throws JMSException;
>
> /**
> * Returns whether the message body is capable of being assigned to the
> * specified type. If this method returns true then a subsequent call to the
> * method <code>getBody</code> with the same type argument would not throw a
> * MessageFormatException.
> * <p>
> * If the message is a <code>StreamMessage</code> then false is returned. If
> * the message is a <code>ObjectMessage</code> and object deserialization
> * fails then false is returned. If the message has no body then true is
> * returned.
> *
> * @param c
> * The specified type <br/>
> * If the message is a <code>TextMessage</code> then method will
> * only return true if this parameter is set to
> * <code>String.class</code> or another class to which a String
> * is assignable. <br/>
> * If the message is a <code>ObjectMessage</code> then this
> * method will only return true if this parameter is set to
> * <code>java.io.Serializable.class</code> or another class to
> * which the payload is assignable. <br/>
> * If the message is a <code>MapMessage</code> then this method
> * will only return true if this parameter is set to
> * <code>java.util.Map.class</code>. <br/>
> * If the message is a <code>BytesMessage</code> then this this
> * method will only return true if this parameter is set to
> * <code>byte[].class</code>.
> *
> * @return whether the message body is capable of being assigned to the
> * specified type
> *
> * @exception JMSException
> * if the JMS provider fails to return a value due to some
> * internal error.
> * @exception MessageNotReadableException
> * if the message is a <code>BytesMessage</code> and the
> * message is in write-only mode.
> */
> boolean isBodyAssignableTo(Class c) throws JMSException;