MapMessage object is used to send a set of name-value pairs. The names are String objects, and the values are primitive data types in the Java programming language. The names must have a value that is not null, and not an empty string. The entries can be accessed sequentially or randomly by name. The order of the entries is undefined. MapMessage inherits from the Message interface and adds a message body that contains a Map. The primitive types can be read or written explicitly using methods for each type. They may also be read or written generically as objects. For instance, a call to MapMessage.setInt("foo", 6) is equivalent to MapMessage.setObject("foo", new Integer(6)). Both forms are provided, because the explicit form is convenient for static programming, and the object form is needed when types are not known at compile time.
When a client receives a MapMessage, it is in read-only mode. If a client attempts to write to the message at this point, a MessageNotWriteableException is thrown. If clearBody is called, the message can now be both read from and written to.
MapMessage objects support the following conversion table. The marked cases must be supported. The unmarked cases must throw a JMSException. The String -to-primitive conversions may throw a runtime exception if the primitive's valueOf() method does not accept it as a valid String representation of the primitive.
A value written as the row type can be read as the column type.
| | boolean byte short char int long float double String byte[] |---------------------------------------------------------------------- |boolean | X X |byte | X X X X X |short | X X X X |char | X X |int | X X X |long | X X |float | X X X |double | X X |String | X X X X X X X X |byte[] | X |----------------------------------------------------------------------
Attempting to read a null value as a primitive type must be treated as calling the primitive's corresponding valueOf(String) conversion method with a null value. Since char does not support a String conversion, attempting to read a null value as a char must throw a NullPointerException.
@see javax.jms.Session#createMapMessage()
@see javax.jms.BytesMessage
@see javax.jms.Message
@see javax.jms.ObjectMessage
@see javax.jms.StreamMessage
@see javax.jms.TextMessage
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