O'Reilly - Java Message Service

publisher.publish(message);
...
// A message consumer reads the properties
String name = (String)message.getObjectProperty("username");
Double limit = (Double)message.setObjectProperty("Limit");
Boolean isApproved = (Boolean)message.setObjectProperty("IsApproved");
C.3 Read-Only Properties
Java Message Service
Once a message is produced (sent), its properties become read-only; the properties cannot
be changed. While consumers can read the properties using the property accessor methods
(getProperty( )), they cannot modify the properties using any of the mutator
methods (setProperty( )). If the consumer attempts to set a property, the mutator
method throws a javax.jms.MessageNotWriteableException.
Once a message is received, the only way its properties can be changed is by clearing out
all the properties using the clearProperties( ) method. This removes all the properties
from the message so that new ones can be added. Individual properties cannot be modified
or removed once a message is sent.
C.4 Property Value Conversion
The JMS specification defines rules for conversion of property values, so that, for
example, a property value of type int can be read as a long:
Message message = topicSession.createMessage( );
// Set the property "Age" as an int value
message.setIntProperty("Age", 72);
...
// Read the property "Age" as a long is legal
long age = message.getLongProperty("Age");
The conversion rules are fairly simple, as shown in Table C.1. A property value can be set
as one primitive type or String, and read as one of the other value types.
Table C.1. Property Type Conversions
Message.setProperty( ) Message.getProperty( )
boolean boolean, String
byte byte, short, int, long, String
short short, int, long, String
int int, long, String
long long, String
float float, double, String
double double, String
String
String, boolean, byte, short, int, long, float,
double
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