Messages:
The ultimate purpose of a JMS application is to produce and to consume messages that can then be used by other software applications. JMS messages have a basic format that is simple but highly flexible, allowing you to create messages that match formats used by non-JMS applications on heterogeneous platforms.
A JMS message has three parts:
• A header
• Properties (optional)
• A body (optional)
Message Headers:
A JMS message header contains a number of predefined fields that contain values that both clients and providers use to identify and to route messages.
Each header field has associated setter and getter methods, which are documented in the description of the Message interface. Some header fields are intended to be set by a client, but many are set automatically by the send or the publish method, which overrides any client-set values.
JMS Message Header Field Values Are Set
Header Field Set By
JMSDestination send or publish method
JMSDeliveryMode send or publish method
JMSExpiration send or publish method
JMSPriority send or publish method
JMSMessageID send or publish method
JMSTimestamp send or publish method
JMSCorrelationID Client
JMSReplyTo Client
JMSType Client
JMSRedelivered JMS provider
Message Properties:
The JMS API provides some predefined property names that a provider may support. The use of either predefined properties or user-defined properties is optional.
Message Bodies:
The JMS API defines five message body formats, also called message types, which allow you to send and to receive data in many different forms and provide compatibility with existing messaging formats.
Message Type Body Contains
TextMessage A java.lang.String object (for example, the contents of anExtensible Markup Language file).
MapMessage A set of name/value pairs, with names as String objects and values as primitive types in the Java programming language. The entries can be accessed sequentially by enumerator or randomly by name. The order of the entries is undefined.
BytesMessage A stream of uninterpreted bytes. This message type is for literally encoding a body to match an existing message format.
StreamMessage A stream of primitive values in the Java programming language, filled and read sequentially.
ObjectMessage A Serializable object in the Java programming language.
Message Nothing. Composed of header fields and properties only. This message type is useful when a message body is not required.
The JMS API provides methods for creating messages of each type and for filling in their contents. For example, to create and send a TextMessage to a queue, you might use the following statements:
TextMessage message = queueSession.createTextMessage();
message.setText(msg_text); // msg_text is a String
queueSender.send(message);
Exception Handling:
The root class for exceptions thrown by JMS API methods is JMSException. Catching JMSException provides a generic way of handling all exceptions related to the JMS API.
The JMSException class includes the following subclasses:
• IllegalStateException
• InvalidClientIDException
• InvalidDestinationException
• InvalidSelectorException
• JMSSecurityException
• MessageEOFException
• MessageFormatException
• MessageNotReadableException
• MessageNotWriteableException
• ResourceAllocationException
• TransactionInProgressException
• TransactionRolledBackException
The ultimate purpose of a JMS application is to produce and to consume messages that can then be used by other software applications. JMS messages have a basic format that is simple but highly flexible, allowing you to create messages that match formats used by non-JMS applications on heterogeneous platforms.
A JMS message has three parts:
• A header
• Properties (optional)
• A body (optional)
Message Headers:
A JMS message header contains a number of predefined fields that contain values that both clients and providers use to identify and to route messages.
Each header field has associated setter and getter methods, which are documented in the description of the Message interface. Some header fields are intended to be set by a client, but many are set automatically by the send or the publish method, which overrides any client-set values.
JMS Message Header Field Values Are Set
Header Field Set By
JMSDestination send or publish method
JMSDeliveryMode send or publish method
JMSExpiration send or publish method
JMSPriority send or publish method
JMSMessageID send or publish method
JMSTimestamp send or publish method
JMSCorrelationID Client
JMSReplyTo Client
JMSType Client
JMSRedelivered JMS provider
Message Properties:
The JMS API provides some predefined property names that a provider may support. The use of either predefined properties or user-defined properties is optional.
Message Bodies:
The JMS API defines five message body formats, also called message types, which allow you to send and to receive data in many different forms and provide compatibility with existing messaging formats.
Message Type Body Contains
TextMessage A java.lang.String object (for example, the contents of anExtensible Markup Language file).
MapMessage A set of name/value pairs, with names as String objects and values as primitive types in the Java programming language. The entries can be accessed sequentially by enumerator or randomly by name. The order of the entries is undefined.
BytesMessage A stream of uninterpreted bytes. This message type is for literally encoding a body to match an existing message format.
StreamMessage A stream of primitive values in the Java programming language, filled and read sequentially.
ObjectMessage A Serializable object in the Java programming language.
Message Nothing. Composed of header fields and properties only. This message type is useful when a message body is not required.
The JMS API provides methods for creating messages of each type and for filling in their contents. For example, to create and send a TextMessage to a queue, you might use the following statements:
TextMessage message = queueSession.createTextMessage();
message.setText(msg_text); // msg_text is a String
queueSender.send(message);
Exception Handling:
The root class for exceptions thrown by JMS API methods is JMSException. Catching JMSException provides a generic way of handling all exceptions related to the JMS API.
The JMSException class includes the following subclasses:
• IllegalStateException
• InvalidClientIDException
• InvalidDestinationException
• InvalidSelectorException
• JMSSecurityException
• MessageEOFException
• MessageFormatException
• MessageNotReadableException
• MessageNotWriteableException
• ResourceAllocationException
• TransactionInProgressException
• TransactionRolledBackException
